ALBERT

Description: SummaryIn four consecutive experiments, plasma uric acid (PUA), hepatic xanthine dehydrogenase (XDH) and body-weight gains (WG) of broiler chickens were measured under varying dietary methionine, protein and energy. In Expt 1, increases in WG with increasing dietary methionine peaked at 0·60%, a level where the initial decreases in either PUA or XDH reached a minimum. PUA and XDH in broiler finishers (Expt 2) decreased between 0·26 and 0·50% dietary methionine while WG improved between 0·26 and 0·50% methionine. XDH in the 18% protein and 0·68% methionine + cystine (MC) diet combination for Expt 3 was 66·4 μtmol/10 min/total liver weight, a value higher than either the 43·5 or 46·5 μtmol/10 min/total liver weight, respectively obtained in the 21% protein + 0·68% MC and 24% protein + 0·68% MC diet combinations. Both PUA and XDH, however, increased with increasing dietary protein when MC was either 0·76 or 0·84% diet. XDH in Expt 4 decreased between 11·7 and 13·4 MJ ME/kg diet that contained either 0·76 or 0·84% MC, tending not to vary between 13·4 and 15·1 MJ ME/kg diet. This enzyme activity remained essentially similar between 11·7 and 15·1 MJ ME/kg diet that contained 0·68% MC.

Description: SummaryFrom 1980 to 1982 fungicide and aphioide sprays were tested in factorial combination with four amounts of nitrogen fertilizer, applied in one or two dressings to winter wheat, on three contrasting clay soils. These experiments were at Hexton (Burwell series) in Hertfordshire, at Billington (Evesham series) and at Maulden (Hanslope series) in Bedfordshire, following a 2–year break, an all-cereal rotation, and continuous wheat respectively. The nitrogen dressings were calculated after taking into account mineral N in the soil. In 1981 and 1982 soil density was measured by penetrometer. This showed compaction in soil at Maulden 28 cm deep which caused waterlogging in spring; this delayed growth which was not made good later.At Hexton a small seed rate was used; plant losses during winter were proportionally larger than elsewhere. At Billington, the maximum number of stems occurred in March and elsewhere in April. Despite these differences in seed rate and number of plants, number of ears varied little, and each year the wheat at Hexton accumulated dry matter most rapidly. The growth rate there ranged from 20·0 to 21·8 g/m2/day during the linear growth phase as compared with 14·4 to 16·6 g/m2/day at the other two sites. Giving N in two dressings rather than in one increased dry-matter yield at all sites in May, but later this benefit remained static and so became a smaller proportion of the total. Fungicides increased post-anthesis dry-matter yield by 0·75 t/ha, most of which was incorporated in the grain.Mean grain yields from 1980 to 1982 where nitrogen fertilizer was given were 9·86 t/ha at Hexton, 7·88 t/ha at Billington and 6–91 t/ha at Maulden. Additional nitrogen fertilizer always increased grain yield when fungicides and aphicides were given, but not where they were not. Grain yields in excess of 10 t/ha were achieved with numbers of ears ranging between 360 and 435/m2. The components of yield showed that grain yield was related to the number of grains per ear and 1000·grain weight, but not number of ears. Grain weight was increased by 3·1 mg by the fungicides.The fungicides controlled the diseases eyespot (Pseudocercosporella herpolrichoides), Septoria spp. and yellow and brown rust (Pucdnia striiformis and P. recondita) where they occurred, but even where these diseases were absent or at very low levels the fungicides significantly increased grain yield. At Billington and Maulden take-all (Qaeumannomyces graminis) infected between 44 and 90% of the plants and sharp eyespot (Rhizoctonia cerealis) infected from 〈 1 to 20% of the stems because the wheat followed cereals. Yields of straw behind the combine-harvester were from 50 to 70% of those obtained from sheaves cut at ground level.

Description: Major economic losses in many agricultural crops have been attributed to damage caused by insects of Heliothis spp. For example, Alcock & Twine (1980) estimated that in Queensland, Australia the annual losses caused by Heliothis spp. were over $16 million, with major losses in sorghum, cotton, tomatoes, tobacco, and safflower. The increasing resistance of Heliothis spp. to pesticides together with an increasing awareness of environmental problems associated with excessive use of pesticides has encouraged the development of research into the area of host-plant resistance. Naturally occurring toxicants and repellants, feeding deterrents and sex pheromones have been evaluated for some years (Jacobson, 1982; Lukefahr, 1982).

Description: SUMMARYThe development of the acrosomic system and the spermatid nucleus were used to define 14 stages of the seminiferous epithelial cycle in goats; these stages provided a basis for the examination of the behaviour of different spermatogenic cells which gave an idea of the efficiency of spermatogenesis. Eighteen steps of acrosome development (spermiogenesis) were observed in testicular material stained with periodic acid-Schiff. The first 14 steps were used to classify SEC into 14 (I–XIV) stages which in turn were employed to study the pattern of differentiation of spermatogenic cells by counting them in each stage of the cycle. Three generations of type A (A1, A2, A3), one generation of type intermediate (In) and two generations of type B (B1, B2) spermatogonia could be distinguished. A1 spermatogonia divided primarily in stages IX–X to produce A2 spermatogonia which in turn divided in stages XII–XIII to produce A3 spermatogonia and A, spermatogonia. A3 spermatogonia divided in stage XIV to produce In spermatogonia whereas A1 spermatogonia did not divide till the next cycle but underwent 26·3 % degeneration. In spermatogonia divided to form B1 spermatogonia in stages III–V which further divided to produce B2 spermatogonia in stage VI. Types A3, In and B2 spermatogonia showed 15·0, 25·0 and 25·8% degeneration respectively. B2 spermatogonia divided in stages VII–VIII to produce double the number of primary spermatocytes which persisted without any degeneration till stage XIII of the following cycle and divided at the beginning of stage XIV to form double the number of secondary spermatocytes. These cells divided at the end of stage XIV to form less than double the number of young round spermatids, showing 10·4% degeneration. It is concluded that the development of the acrosomic system as well as the spermatid nucleus could be conveniently used to study the behaviour of spermatogenic cells and that the process of spermatogenesis was less efficient than thought previously.

Description: SUMMARYField experiments were made during the rainy seasons of 1979 and 1980 at Hissar, India, to study the effect of time of weed removal on the yield of groundnut. Removing weeds from 2 to 8 weeks after sowing led to significantly larger yields than that of plots which were not weeded. Maximum pod yield in both years was obtained when weeds were removed 4 weeks after crop sowing.

Description: The potential benefits of high-energy supplements, such as cereal grains, for grazing ruminants are commonly eroded by an accompanying depression in the digestion and intake of the basal herbage (McCullough, 1959). Low ruminal pH (〈 6·0) induced by the rapid rate of production of the acids of starch fermentation, and competition between cellulolytie and amylolytic bacteria for limited nutrients, are known to be responsible for inhibition of cellulolysis (Terry, Tilley & Outen, 1969; Stewart, 1977; el Shazly, Dehority & Johnson, 1961). However, there are reports of reduced roughage digestion when nutrients appear to be non-limiting and pH is maintained above 6·0 (Gilchrist et al. 1979; Henning et al. 1980). The possibility remains that intermediates or end products of starch digestion have specific inhibitory effects on the numbers of cellulolytie organisms or on the activity of their extracellular cellulases.

Description: SUMMARYVascular and non-vascular cell walls were isolated separately from leaves, upper stems and lower stems of 12 kale (Brassica oleracea L.) cultivars, by a sieving technique. The digestible organic matter in the dry matter (DOMD) of the cell walls and of the whole plants was determined by pepsin-cellulase digestion. The measured whole-plant DOMD correlated closely with the DOMD predicted by adding together the amounts of non-digested material derived from all the plant's component cell-wall fractions. Differences in DOMD between cultivars were determined primarily by the amount of vascular cell walls in the stems, particularly the lower stems; that is, by the stem anatomy. The vascular cell walls of the upper stems had a wider range of DOMD values and a higher mean DOMD than the vascular cell walls of the lower stems. Thus cell-wall composition made some contribution to determining the whole-plant DOMD, although it contributed less than the anatomy of the stem.

Description: SUMMARYEffects of three levels of N application and four intervals between harvests on field swards of perennial ryegrass (Lolium perenne L.) were studied during 6-week periods in summer and spring. Ryegrass was compared with tall fescue (Festuca arundinacea Schreb.) in spring and autumn.The application of N increased the rate of production of leaf primordia, the number of leaf primordia per tiller, the length of the shoot apex, the rate of development of primordia into unemerged leaves, the number of leaves emerging, the number of live, emerged leaves per tiller, the leaf extension rate and weight of blade emerging and the net gain, per tiller per day, in blade length and weight. The application of N tended to reduce the number of unemerged leaves per tiller and the length of apex per primordium. Applied N retarded leaf death (whether measured as numbers, length or weight) during the first 2–3 weeks after application and accelerated death subsequently. During the 1st week of the summer periods, the net gain in green blade length and weight per tiller was doubled by 22 kg N/ha and trebled by 66 kg N (compared with nil). During the final fortnight of the summer periods, the net gain in green blade length and weight was less with the 6-than with the 3- or 2-week interval, and, in the case of the 6-week interval, the positive effect of applied N on the rate of development of primordia into unemerged leaves and on the number of leaves emerging had been lost.The ryegrass had more leaf primordia and unemerged leaves per tiller than the fescue, and a faster rate of development of primordia into unemerged leaves and of unemerged into emerged leaves.A ryegrass leaf spent a broadly similar length of time in each of the three stages, primordium, unemerged leaf and fully expanded live leaf, and about half as long as one of those stages as an emerging leaf. At nil N a leaf developed to about 6000 times its starting length (as a newly-formed primordium) in 67 days in summer; at high N a leaf developed to about 10500 times its starting length in 53 days. The percentage increase in length per day was greatest during the unemerged leaf stage.

Description: SUMMARYIn Expt 1 the efficiency of absorption of phosphorus in feedingstuffs was compared within four sets of 18-month-old, chimaera-derived triplets; 12 feedingstuffs were evaluated in four balance trials with 32P. Seven diets consisted of a P-rich ingredient mixed with a low-P basic diet and five of hay or pelleted dried grass or lucerne. The P ingredients tested were the protein-rich meals, rape, soya-bean, maize gluten, fishmeal and rice bran, and the cereals, barley and wheat.Sets of triplets absorbed dietary P with different (P 〈 0·001) efficiencies; the mean values were 0·72, 0·63, 0·76 and 0·79. The availability of P differed (P 〈 0·001) between diets, highest values being seen with the fishmeal (0·80), barley (0·78) and wheat diets (0·78) and the lowest with rice bran (0·63) and a perennial ryegrass hay (0·64). There was no evidence for an age effect on efficiency of absorption.Endogenous faecal excretion was positively related to intake (P 〈 0·001) and negatively related to efficiency of absorption of dietary P. Plasma concentration was positively related (P 〈 0·001) to both intake and, between sets, to the efficiency of absorption.Significant urinary excretion of P generally occurred when the efficiency of absorption was greater than 0·70. Two members of a set which absorbed P with high efficiency and excreted low volumes of urine died from urethral obstruction caused by calculi.In Expt 2 an estimate of the variation in the concentration of P in plasma of 48 ewes on a barley-based diet was assessed and the values for three of the chimaera sets fell within the top quartile.Safety factors were calculated from the animal and plant variations in the efficiency of absorption of dietary P and used to determine dietary allowances for different classes of sheep.

Description: SUMMARYCommercial Celery Cultivars Varied in their response to inoculation by celery mosaic virus. The most severe symptoms occurred in self-blanching cultivars, but a high level of resistance was found in some non self-blanching cultivars such as Solid White and Fordhook. The resistance in these cultivars was confirmed in glasshouse tests.

Description: SUMMARYA method of assessing colour of grass leaves was developed to distinguish between cultivars. Leaves from a representative population of 60 plants of each cultivar were measured. To eliminate subjective judgment a colour difference meter was used, giving tristimulus values X, Y and Z (approximating to red, green and blue respectively), from which the colour co-ordinates L, a and b of the Commission Internationale de L'Eclairage system were calculated.In a pilot study two visually distinguishable perennial ryegrass cultivars were easily separated (P

Description: The changeover from fertilizers containing calcium or ammonium sulphate to those containing little or no sulphur has led to the occurrence of sulphur deficiency in many areas of the world (McNaught & Christoffels, 1961). In the United Kingdom, it was thought that even in the absence of fertilizer sulphur, atmospheric inputs were sufficient to ensure an adequate supply for crops. Recent work in the north of Scotland has shown that this is not so, that many soils in the area are low in sulphur, and yield responses have been obtained following application of sulphur to grass (Soott et al. 1983; Scott, 1984). The purpose of the present experiments was to extend the work to cereals, in particular to examine the response to added sulphur of the grain yield of winter barley, and to measure the effect of sulphur on the chemical composition of plants.

Description: Crop residues, consisting of cereal stovers and hays made from the vegetative parts of grain legumes, are important dry-season feeds for ruminant livestock in the Savannah Zone of West Africa (van Raay, 1975; McCown, Haaland & de Haan, 1979; Jahnke, 1982). With the increasing demand on land to produce more crops and animal products, traditional systems are under pressure. There is need for a reliable means to quantify the supply of feed from various sources and to monitor the type, quantity and quality of crop residue available to livestock.

Description: In the recent past, specific gravity of tubers has been considered an easy means of estimating yield potential of sweet potato cultivars (Bryant, 1979) and their quality characters like starch value and dry-matter content (Ishikawa & Sakai, 1973). Bryant (1979) separated sweet potato tubers with low and high specific gravity at planting time by determining whether or not they floated in water, and observed that the floaters gave 20% higher yield than the sinkers. As this simple test claimed to hold promise for selecting higher-yielding sweet potato genotypes, it was decided to scan its usefulness at the College of Agriculture, Dholi, where a large collection of sweet potato germ plasm is being maintained for research needs.

Description: The measurement of the nitrogen (N) content of plant material, used as an assessment of protein concentration, is important in determining the quality of various crops for feeding and processing. The generally accepted reference procedure for the direct measurement of N is the Kjeldahl method (Horwitz, 1980), first introduced 100 years ago (Kjeldahl, 1883). Recently a number of alternative direct (Williams et al. 1978) and indirect (Starr, Morgan & Smith, 1981) methods have become available.

Description: SUMMARYA nutrient indexing survey of the soils and rice crop was conducted on 300 fields of four villages in some floodplain areas of Ludhiana. The soils are, in general, alkaline in reaction, highly calcareous, medium in organic matter and mostly heavy in texture. Soil analysis (DTPA extraction) indicated that about 27% are deficient in available zinc. Leaf analysis indicated the concentration of N, Zn, Cu, Fe and B to be below their critical levels in 27, 25, 93, 39 and 6% of the samples respectively: the low levels of Cu(l–3 μg/g) are considered as a ‘hidden hunger’ as the crop lacked any visual Cudeficiency symptoms.Correlation studies indicated the absence of any relationship between the micronutrient status of the soils, assessed by DTPA extraction, and leaf content. Consequently leaf analysis is recommended for evaluating the nutritional disorders of lowland rice.

Description: SummaryDaily supplements of dried Leucaena leaf meal (500 g/head) were offered for 3 weeks to steers in metabolism cages. The steers had previously been fed diets of oaten chaff (5 kg/head/day) ormclasses and urea (4·5 kg/head/day) with restricted forage (2 kg/head/day). Excretion rates of the primary degradation product of mimosine, 3-hydroxy-4(1H) pyridone (DHP) by steers fed the two diets were compared. These compounds appeared in urine on the 1st day after Leucaena feeding had commenced and output remained fairly constant after 4 days. Mean weekly urinary outputs (g) of DHP from steers fed the oaten chaff or molasses + urea diet were 13·45 and 7·50 respectively. These levels corresponded to 0·23 and 0·13 of the amounts ingested. When steers were fed the molasses + urea diet, DHP continued to appear in urine up to 5 days after Leucaena had been withdrawn from the diet. On the oaten chaff diet no DHP was detected after 3 days following withdrawal of Leucaena.The effects of casein or formaldehyde-treated casein supplements on the output of urinary DHP by steers fed oaten chaff plus Leucaena was evaluated in a second experiment which ran concurrently. The animals were fed the test diets for 3 weeks before collections were made. Mean DHP outputs (g/day) from animals fed the control diet, control diet plus casein or control diet plus formaldehyde-treated casein were 1·89, 2·21 and 2·44 respectively.These results confirm substantial degradation of DHP and that the extent of degradation can be affected by the dietary regime in which Leucaena is fed.

Description: SummaryThree trials were conducted over two cropping seasons, on portions of the production fields of the Nigerian Sugar Company sugar-cane estate, Bacita, to evaluate the efficacy of several herbicide mixtures for weed control in sugar cane using the varieties Co. 957 and Co. 1001. With a broad spectrum of weeds, early post-emergence applications of diuron + hexazinone (2·0 + 0·7 kg a.i./ha) followed by hexazinone + paraquat (0·5 + 0·3 kg a.i./ha) about 8 weeks after the first application gave satisfactory weed control that resulted in high cane yields. Addition of glyphosate to the mixture for the first application or its substitution for paraquat in the second application, or both, resulted in increased suppression of nutsedge. This was, however, more phytotoxic to the sugar-cane plants. Addition of pendimethalin to either diuron or hexazinone improved the control of grass weeds. Hexazinone-based mixtures were found to give longer-lasting weed control than the diuron-based mixtures. Both diuron and hexazinone were generally more selective on Co. 957 than on Co. 1001. The degree of weed infestation between 6 and 12 weeks after planting was inversely related to cane yield.

Description: SummaryThe soils of fields where winter wheat yields were measured for the I.C.I. Ten Tonne Club Survey in 1979 and 1980 were identified according to the soil series recognized by the Soil Survey of England and Wales. The yield distributions were almost normal, with means 1·49 and 1·60 t/ha greater than the national average. Soil series accounted for 18–19% of the yield variance in both years, which was much more than any other single factor measured. If introduced in best order, soil series, crop variety, previous crop and sowing date accounted for 31% of the variance in both years. However, classes based on soil particle size and drainage, as derived from series identifications, accounted for very little of the variance. Only thick brickearth (loess) soils gave greater mean yields in both years than the overall means of all sites where series were identified. The same soil types provided 35% of the sites where 〉 10 t/ha was achieved in either year, though a wide range of soil types gave such large yields.Yields were greater in 1980 than in 1979 in almost all parts of the country. Although rainfall was only slightly less in the spring and early summer of 1980 than in the same period in 1979, many parts of the country suffered large potential soil moisture deficits in 1980, but these decreased yields slightly on a few series only. Factors other than rainfall used to calculate soil moisture deficits (radiation or wind) probably affected yields much more than rainfall itself.

Description: SummaryAn analysis of data from the complete dissection of one side from 285 animals from a breed comparison experiment was conducted to determine whether there were important biases in the prediction of percentage lean in the side based on dissection of the rumpback joint and, if so, whether the dissection of any of five other sample joints would have been better.For estimating lean content of the side, it was found that the lean content of any sample joint except the hand was a more precise predictor than standard carcass measurements alone, while including the latter in a prediction equation based on a single sample joint dissection improved precision further. For prediction based on lean in the sample joint alone, any one of the ribback, ham and rumpback was best. If other carcass measurements were included (in particular, C fat depth, eye-muscle area and trimming percentage were found to be useful), there was little to choose between the joints. For all joints there were differences between sire breeds (Large White, Canadian Yorkshire, U.S. Duroc, U.S. Yorkshire, Danish Landrace or Norwegian Landrace), sexes (hog or gilt) and feeding regimens (ad libitum or scale) in lean content of the side at constant lean content of the sample joint, but the regression slopes differed only when the rumpback or streak was used as a predictor, and then only between ad libitum and scale-fed pigs. It will therefore be important in any future such experiment fully to dissect a sample of each class (breed, feeding regimen and sex) to provide unbiased estimates of the differences in lean content. A sample of 30 from each class should allow the differences to be estimated adequately.

Description: SummaryExperiments testing the effects of variety, sowing date, seed rate, amount and time of application of nitrogenous fertilizer in the spring, application of nitrogenous fertilizerin the autumn and disease control at four sites in the north of England in 1980, 1981 and 1982 are described and the results are discussed.The siting of the experiments and the seasons had important effects on grain yield and influenced the response to the total amount of nitrogen used and to disease control. The other husbandry factors produced more consistent effects. The choice of variety and drilling date had thegreatest influence on yield. The responses to the different seed rates, to the method of applying nitrogenous fertilizer and to autumn-applied nitrogen were smaller. The effects were additive.It is argued that differences in the efficiency of light interception by the foliage affects grain yield; that light interception may be influenced by the state of the foliage at the start of the period of rapid growth from April onwards; and that site, season and husbandry all affect the development of the crop up to that point.

Description: SummaryThe seasonal and post-partum oestrus occurrence and ovarian activity, assessed by the plasma progesterone concentrations, were studied in Finn-cross ewes following autumn and winter lambings.The last seasonal oestrous cycle was followed by a silent ovulation in C0% of the Finn × Awassi ewes. Silent ovulations during midanoestrus occurred in 50% of the ewes, and in 90% of the animals a silent ovulation preceded the normal resumption of the seasonal sexual activity.The first post-partum oestrus occurred within C0 days after October lambings in about 90% of the ewes. Silent ovulations before the first post-partum oestrus were evident in 70% of the recycling ewes.It is suggested that breeding ewes with ovarian activity after oestrus induction during anoestrous periods might increase the reproductive performance of the flock in a frequent lambing system.

Description: SummaryNormal and brown midrib-3 (bm3) maize plants of three genotypes (Inra 188, Inra 240 and Inra 258) were sampled at three stages of maturity. Whole crop and plant components were analysed for in vitro digestible organic matter in the dry matter (DOMD) and the concentration of neutral detergent fibre, cellulose, hemicellulose, xylose, soluble sugars, starch and total nitrogen in the dry matter.The concentrations of total nitrogen, neutral detergent fibre, cellulose, hemicellulose and xylose were similar in both normal and bm3 plants. Xylose was the main constituent sugar of hemicellulose forming 70–75% of the total hemicellulose. The higher concentration of soluble sugars and lower concentration of starch in the bm3 plants was attributed to the later maturity of the bm3 plants.The bm3 gene significantly reduced lignin synthesis in the whole plant and plant components at all harvests. The mean concentration of lignin in the normal and bm3 plants were 2·2 and 1·4%, respectively. The ferulic and p-coumaric acid concentrations in the bm3 plants were 1·31 and 0·93 mg/g D.M. compared with 1·59 and 1·16 mg/g D.M. for the normal plants, respectively.The in vitro DOMD values for the bm3 plants were significantly higher (P 〈 0.05) than their normal counterparts.

Description: SummaryIn each of the years from September 1977 to July 1982 winter wheat was grown on one or more of three clay soil sites (clay content 35–55%) in Oxfordshire where the climate is close to the average for the area of England growing winter cereals.The effects on crop water use of different soil management practices, including ploughing, direct drilling and subsoil drainage, are compared. Cultivation treatment had little effect on the maximum depth of water extraction, which on average in these clay soils was 1·54 m below the soil surface. Maximum soil water deficit was also little affected by cultivation; the maximum recorded value was 186±7·6 mm. Subsoil drainage increased the maximum depth of water extraction by approximately 15 cm and the maximum soil water deficit by about 17 mm.Generally soil management had little effect on either total water use by the crop which was found to be close to the potential evaporation estimated by the method of Penman, or water use efficiency which for these crops was about 52 kg/ha par mm water used.Results are discussed in relation to limitations to potential yield.

Description: SummaryGabriel (1971) proposed a technique for displaying the rows and columns of a twoway table as a two-dimensional biplot so that any element of the table can be approximated by the inner product of vectors corresponding to the appropriate row and column. The technique is useful for investigating the pattern of response of varieties over different environments, and substantially increases the information available from the more familiar methods of regression and principal component analysis without need for additional computation.

Description: SummaryThe ruminal metabolism of lactic acid was investigated in vivo under normal feeding conditions in four sheep each adapted to one of the following diets: high-concentrate, intermediate, high-roughage containing 65, 43 or 10% maize meal and molasses respectively, or lucerne hay. A continuous basal turnover of ruminal lactate (0·01–0·02 mmol/1/min) was found which increased 10- to 40-fold immediately after feeding when production exceeded utilization and lactate accumulated in the rumen. This was followed by an increase in utilization rate which removed the accumulated lactate. Both lactate and glucose turnover were related to the amount of readily fermentable carbohydrate in the diet. Approximately 8, 6·5, 5 and 2·5% of the total VFA was formed through lactate on the high-concentrate, intermediate, high-roughage and lucerne hay diets respectively.Rumen microbial counts of total culturable, glucolytic, amylolytic and lactateutilizing bacteria, and of ciliate protozoa were also performed on the four sheep. Numbers of micro-organisms in all groups were highest on the high-concentrate diet and lowest on the two roughage diets. The proportions of the predominant genera from the different metabolic groups of bacteria differed, although in most cases the same organisms were present in the rumen on all diets. The succinate pathway was found to be quantitatively more important in the conversion of lactate to propionate in the rumen. Although the numbers of lactate-utilizing bacteria increased as the amount of RFC in the diet increased, their metabolic activity was actually lower. Reasons for this finding are discussed, together with factors influencing the regulation of lactate production and utilization in the rumen.

Description: SummarySixty families of each of two tomato triple test crosses (S 120 × EC 61747 and EC 31513 × Pusa Ruby) were raised in completely randomized blocks in two replications with two fertilizer levels. Perkins & Jinks' (1971) analysis was used to detect and measure the interactions of additive, dominance and epistatic effects of genes with micro- and macro-environments for flowering time, maturity period, number of branches, final height, number of locules, number of fruits per plant, yields per plant and weight per fruit. Additive and dominance gene effects were almost equally sensitive to micro- and to macro-environments. The j and l type epistasis was more sensitive to the environments than the i type epistasis.

Description: SummaryThe growth of Huia white clover was followed in undisturbed and unsterilized soil cores containing a normal endomycorrhizal fungal population which had been inoculated with one of eight additional endomycorrhizal fungal isolates. Most of the endophytes significantly stimulated growth over filtrate controls at some stage in the experiment. Glomus mosseae, G. tenue and Gigaspora margarita produced large growth increments over a range of applied phosphorus levels. The inocula also contained a filtrable agent that was capable of reducing the growth of white clover.

Description: SummaryTwo digestion trials were performed with sheep in order to assess the effect of the sulphur dioxide treatment on the digestibility of wheat straw in vivo. In the first trial, untreated and SO2-treated straw served as the major components of the diets. Sulphur dioxide partly solubilized the cell wall (CW) material of the straw, decreasing its content from 78·5 to 55·9%. The digestibility of the residual CW was increased from 49·2 to 77·8%, whereas the digestibility values of the cell-soluble fraction (CS) were unaffected by the treatment: 55·8 and 57·8% for the untreated and treated straw, respectively. Apparent digestibility of the organic matter (OM) was increased by the treatment from 46 to 65%.In the second trial SO2-treated wheat straw was fed together with concentrates at a D.M. ratio of 30/70, and the digestibility of the OM and CW was determined.CW and OM digestibilities of the treated straw were not affected by 70% concentrate in the diet and the respective values were 77·0 and 65·5%, very similar to those found in the first trial. The reason for the in vitro–in vivo discrepancy is discussed.

Description: SummaryThe relationship between structure and the ability of piglet intestine to transport alanine has been determined during the first few weeks of postnatal life.Villus length halved without change in crypt depth during the 3rd week of postnatal life. A similar shortening of villi, accompanied by an increase in crypt depth, took place when 2-week-old piglets were weaned on to a solid diet. Weaning piglets at 3 weeks increased crypt depth without causing further shortening of villi.Alanine transport was shown, by quantitative autoradiography, to be largely confined to enterocytes in the region of the villus tip. The way in which this transport function developed was analysed further by fitting logistic growth curves to measurements of intra-enterocyte alanine concentration. The ability of enterocytes to transport alanine occurred earlier and alanine was accumulated to higher concentrations in enterocytes studied in 21- compared with 15-day-old unweaned piglets. Weaning piglets on day15 or 21 and measuring alanine transport 5 days later produced a pattern of development similar to that reported previously for adult animals.Transport of alanine throughout postnatal development showed sodium dependency. Effects of alanine on intestinal short-circuit current of weaned piglets were again similar to those recorded in adult animals.These results are discussed in terms of intestinal adaptation to a changing environment and in relation to the ‘notional capacity’ of a pig villus to transport amino acids during the early postnatal period of development.

Description: SummaryApparent digestibility of forage kale (cv. Maris Kestrel) was compared with that of mixed perennial ryegrass (0·85) and clover (0·15) herbage in two experiments. In a third experiment measurements were made of the partition of digestion between the reticulo-rumen and post-ruminal regions of the digestive tract in sheep fed kale, using intra-ruminal infusion of inert ruthenium phenanthroline and chromium-EDTA markers and time sequence sampling from the duodenum. Results in Expt 3 were compared with predicted values for a range of ruminant diets, including digestion of fresh perennial ryegrass and white clover.In Expts 1 and 2 the ratio of readily fermentable to structural carbohydrate (CHO) was much higher in kale (2·6–3·2) than in mixed ryegrass and clover herbage (0·6), and showed little difference between kale leaf and stem components. Apparent digestibilities of organic matter (OM), cellulose and hemicellulose were 80–90% for kale diets, varied little with changes in leaf/stem ratio, and were generally slightly higher than for mixed ryegrass and clover herbage. Calculated metabolizable energy (ME) concentrations were 12·0 and 11·7 MJ ME/kg D.M. for kale and mixed ryegrass and clover respectively.Despite large intakes of water-soluble CHO and pectins in kale-fed sheep in Expt 3, duodenal flows were small and respectively 92 and 98% of the total amounts digested were digested in the rumen. Ruminal cellulose digestion (95% total digested) was as predicted for normal ruminant diets, but less hemicellulose was digested in the rumen (71% total digested) than predicted. Total N flow at the duodenum was 5 g/day less than N intake, and respectively 27 and 66% of the N apparently digested was accounted for as total N absorption from the rumen and post-ruminal absorption of NAN. Calculated absorption of amino acids from the small intestine was less for the kale diet (14% ME intake) than for diets of fresh perennial ryegrass and white clover (20% ME intake). Possible reasons are that 10% more of the OM ingested was digested in the rumens of sheep fed kale than was predicted, that the ratio of dietary total N/100 g digestible OM was much less for kale (3·7) than for perennial ryegrass and white clover (5·6) diets, and that protein formed a lower proportion of the total N in kale diets (75%) than in diets of ryegrass and clover (90%). Despite 3·3 g of S-methyl-L-cysteine sulphoxide (SMCO) being consumed per day, none was detected in either rumen or duodenal contents or in faeces.In was concluded that complete conversion of SMCO to dimethyl disulphide occurred in the rumen, that dimethyl disulphide may have caused the depression in ruminal digestion of hemicellulose, and that the digestion products of kale are deficient in absorbed amino acids relative to other forms of energy, thus explaining responses to essential amino acid supplementation in lambs grazing kale.

Description: SummaryOne fast-growing acid-producing Rhizobium strain 995 of Vigna radiata was screened for growth behaviour in acid, saline and alkaline media. It grew well in yeast-extract mannitol broth of wide pH range as well as varying concentrations of NaCl, Na2SO4 and MnCl2. Variation in nodulation and N2-fixation efficiency occurred on different varieties of green gram, while strain characteristics were not affected by soil stress.

Description: SummaryVariation in infestation of S. avenae on plots of wheat was assessed by combining techniques of enhancing field infestations with scoring individual shoots according to the number of aphids on them, using a logarithmic scale with base 2. The mean score appeared the most useful way of describing the aphid infestation on each plot.In 1982, the sampling effort required for assessment of S. avenae on many plots was considerably reduced by this approach. The artificial increase in numbers of aphids avoided problems associated with sampling small populations, and the logarithmic classification of shoots reduced the time needed to assess large numbers. Scoring plots as a whole, although much quicker, gave results that differed from the assessments based on shoot sampling, and should be used with caution. The differences observed among cultivars in infestation of adult plants in the field in 1982 were not always the same as those observed on younger plants in the glasshouse.

Description: SummaryA computer simulation model of canopy development in a crop of winter wheat is described. The principal features of the model are the simulation of the emergence, growth and senescence of individual leaves and the production of tiller groups (cohorts) during a defined phenological period, with their survival depending on cohort age and shoot population density.Comparison is made between the model output and early- and late-sown crops from three seasons. The behaviour of the model in response to changes in leaf senescence and tiller production is discussed for crops sown in 1978.

Description: SummaryShoot and root growth and associated leaf and soil water potential relations were compared in three consecutive crops of winter wheat grown in the same field. Despite a profuse root system the crop grown in the second drought year (1976) failed to dry the soil as throughly as the crops in 1975 and 1977. Measurements of plant water potential showed that the restricted utilization of soil water reserves by this crop was associated with failure to make any significant osmotic adjustment, leading to premature loss of leaf turgor and stomatal closure. The implications of these results for models to estimate actual crop evaporation from values of potential evaporation are discussed.

Description: SummarySelection for high-(H) and low-(L) drought-induced abscisic acid (ABA) accumulation in spring wheat was made from a cross between parents which contrasted in the character. By the F5 generation H and L selections were homozygous for ABA accumulation, which differed between the classes by 80%. The selections were evaluated in field experiments in which the amount of available water was varied.In one experiment, in which plots were automatically sheltered from rain, H selections outyielded L selections by an average 0·36 t/ha both when fully irrigated and when water was withheld between anthesis and maturity. The extra grain yield of the H selections was not produced at the expense of additional water requirement in either treatment. When water was withheld during the 4 weeks preceding anthesis, the grain yields of H and L selections were similar, but H selections used less water between 1 May and maturity. Averaged over all treatments the ratio of grain yield to water use was greater for H selections than for L selections by 0·12 t/ha/100 mm. Withholding water caused a reduction in water use and a corresponding reduction in biomass production in both sets of selections.In two trials in which plots were either irrigated weekly or received natural rainfall only, the ratio of grain yield to water use was again greater for H than for L selections, by an average 0·10 t/ha/100 mm.It is concluded that in spring wheat, selection for high levels of ABA accumulation in response to water stress may provide an opportunity of increasing grain yield and water-use efficiency.

Description: SummaryOver a period of 3 years 18 autumn-calving, single suckled, April-weaned cows were stocked at three rates at pasture to gain 132, 70 or 25 kg (H, M and L respectively) between April and August and fed to lose 100, 54 or – 13 kg (H, M and L respectively) while housed between November and April, the relative total energy intake over winter being 0·64, 0·83 and 1·00 respectively. Milk yield was reduced by 2·68 kg/day on the H and 1·25 kg/day on the M treatment and as a result calves gained 37 and 10 kg less respectively over winter than on the L treatment. However, despite poorer calf performance economic considerations would indicate a preference for high weight gain during the grazing season and a corresponding loss over winter.

Description: SummaryCell mass (dry matter per cell) and cell composition (concentrations of DNA, RNA, phospholipids, total N, a-dextran, diaminopimelic acid and 18 common amino acids) of rumen bacteria were measured at various times after feeding sheep chaffed lucerne hay (Medicago sativa L.) once daily. Cell composition was measured with sheep fed once hourly. Total DNA and RNA pool sizes in the rumen were also measured.While cell composition was not affected by level of feed intake (700 g v. 1050 g dry matter/day), total DNA, RNA and D.M. pool sizes in the rumen increased with increasing feed intake. With sheep on the once daily feeding regimen relative rumen pool sizes in rumen digesta at various times after feeding were: RNA, 4 〉 14 〉 0 h; DNA, 4 and 14 〉 0 h; D.M. 4 〉 14 〉 0 h. With the hourly feeding regimen pool sizes were similar to the averaged daily values for sheep fed once daily.When sheep were fed once daily bacterial cell mass, DNA and phospholipid concentrations peaked at 12–14 h after feeding and subsequently decreased to the 0 h value. RNA concentration was maximal at about 4 h after feeding and declined to near the 0 h value at about 14 h. RNA concentrations in bacteria were highly correlated with gas production rates by whole rumen digesta. The ratio RNA:DNA was highest shortly after feeding, decreased to below the 0 h value at about 14 h and then increased to the 0 h value. The relative concentrations of a-dextran in bacteria were: 4 〉 14 〉 0 h. Cell composition witli sheep fed hourly tended to reflect the averaged daily values for sheep fed once daily.These results are discussed with regard to changes in estimated fermentation rate and pool size of bacteria in the rumen. It is suggested that changes in average composition (DNA, RNA, total N and RNA: DNA ratio) of mixed rumen bacteria reflect changes in the average growth rate of the population.

Description: SummaryComputer programs have been developed to evaluate sequential variety selection systems using Monte Carlo and numerical integration methods.These methods are described in the paper and applied to official U.K. cereal variety testing. The consequences of alternative selection systems are examined.

Description: SummaryThe roles of leaves, stems and reproductive parts in 14CO2 fixation and its subsequent movement in winter oil-seed rape, cultivar Jet Neuf, were investigated in two field experiments carried out on the Wye College Farm. The relative importance of these organs changed with time. At early flowering the leaves were the most important photosynthetic organs (66·8% 14CO2 activity). Midway between flowering and maturity the stems became the major supplier of photosynthates, a role eventually taken over by the developing siliquae (pods).These data stress the importance of keeping all photosynthetically active surfaces free from disease if efficient resource utilization and higher yields are to be achieved.

Description: SummaryTwo experiments were undertaken with maize silage, which had been sterilized by subjecting it to a 6 Mrad dose of γ radiation, inoculated with micro-organisms implicated in the aerobic deterioration of silage and subsequently exposed to air. The inocula employed comprised mixed strains of yeasts, bacilli and lactic acid bacteria and combinations of these. The changes which accompanied aerobic deterioration were observed. The major losses of fermentation acids, ethanol, ammonia and dry matter, and increases in total nitrogen and temperature were associated with inocula in which yeasts were represented. Similar changes of a lower magnitude were also observed in silage treated with inocula containing bacteria only, although these were not always accompanied by the growth of these organisms or loss of dry matter. However, when employed in mixed inocula with yeasts, the bacteria proliferated and tended in some instances to increase losses further, suggesting an association between the groups of micro-organisms in the aerobic deterioration process. Losses were also sustained in sterile silage which received no inoculum and the possible reasons for this are discussed.

Description: SummaryWool growth rates (WGR) of individual sheep were measured by a patch-sampling technique, during periods of developmental growth, body-weight loss (which ranged from 21 to 34% of original body weight, at rates between 60 and 150g/day) and subsequent compensatory growth under ad libitum feeding.There was a ‘lag phase’ of about 30 days before WGR appeared to be affected by changes in direction of the animals' growth paths.During body-weight loss WGR declined about 300% more than the percentage change in body weight, with the duration of nutritional stress exerting a greater influence than the rate of body-weight loss.During compensatory growth in body weight, the relationship between WGR and rate of body-weight change was initially negative. Sheep required between 11 and 14 weeks to reach the WGR of 21 g/day found during developmental growth. Compensatory growth of wool did not occur.Duration of the nutritional stress, rather than its severity (as indicated by rate of body-weight loss), was the more important determinant of the time taken for the sheep to regain normal levels of wool growth after the commencement of ad libitum feeding.

Description: SummaryField experiments were conducted during the rainy seasons (June–October) of 1978 and 1979 in order to determine the effect of fertilizer N rates (0, 40, 80 and 120 kg N/ha) on yield and yield attributes of some new sorghum cultivars in northern India. Sorghum hybrid varieties yielded more than pure line varieties, hybrid CSH 5 outyielding all other cultivars including other hybrid varieties because of its greatest number of grains per panicle. Nitrogen application at 80 or 120 kg N/ha brought about significant improvement in number of grains per panicle and yield per ha.Cultivar Χ N rate interactions were significant, in affecting the yield per ha and number of grains per panicle in 1978, whereas such differential response of sorghum cultivars to N rates did not occur in 1979. Sorghum hybrid varieties, even at lower N rates, produced identical yields to the pure line varieties supplied with higher N rates.

Description: SummaryKale of normal and low S-methyl-L-cysteine sulphoxide (SMCO) content was produced by growing the same cultivar in soils of normal (20–30 mg/kg) and low (5–10 mg/ kg) soil sulphate-S concentration. Compared with normal S plots, kale grown in low S plots showed little or no reduction in D.M. yield or total N content, but contained lower concentrations of inorganic sulphate, SMCO and glucosinolates.Replicated plots of normal and low SMCO kale were grazed by lambs for 12-week periods in two consecutive years, using a fixed crop allowance of 2·5 kg D.M./animal/ day. All animals were given injections of copper and iodine, and oral supplements of selenium, to ensure that effects upon animal performance could largely be attributed to differences in kale SMCO concentration.SMCO concentration in the diet consumed by lambs grazing normal and low SMCO kale was respectively 0·60 and 0·35% D.M. Following the onset of kale feeding, all animals developed subclinical haemolytic anaemia which stabilized by week 6, and was more marked during weeks 1–6 than during weeks 7–12. Animals grazing low SMCO kale showed a less severe anaemia than those grazing normal SMCO kale, which was associated with lower blood concentrations of dimethyl disulphide and Heinz bodies, and higher reduced glutathione (GSH) and packed cell volume (PCV) levels. Liveweight gain and wool growth were greater for lambs grazing low than normal SMCO kale during weeks 1–6, corresponding to the period of most severe haemolytic anaemia, but during weeks 7–12 there were no differences between the two groups.It was concluded that SMCO content depressed kale feeding value, with most of the depression occurring in the first 6 weeks of grazing, and that in these experiments the lambs were able to adapt to kale containing 0·6% D.M. as SMCO after 6 weeks of feeding. Endocrine factors involved in this adaptation are discussed.

Description: SummaryThe analysis of plant competition experiments in which all possible pairs of p genotypes are grown in replacement series is discussed. Two methods of analyses, using models of de Wit (1960) and Gleeson & McGilchrist (1980), are compared. The two approaches, which are shown to be linked algebraically, complement each other in terms of agronomic interpretation.

Description: SummaryA replicated, long-term field drainage experiment on a clay soil was started in 1978 to investigate the effects of mole drainage on land that had been direct-drilled or ploughed. We here describe the background and the need for this work, details of the experiment and summarize the results for the first 2 years. The main factors causing point-to-point variability in the soil at the experimental site and their relative contributions were assessed. Variations in inherent soil properties were small, except for depth to calcareous clay. Site hydrology was also generally uniform, especially soil water content, and was little affected by the presence of subsoil drainage schemes dating from the 19th century. There were some variations in micro-relief. The drained and undrained plots were hydrologically separated. Equipment was installed to measure separately surface runoff, lateral flow at the bottom of the cultivated layer (the interflow) and deep drainage from the mole and pipe system (in the drained plots only). The design and performance of that equipment is described. In both years much of the undrained soil became saturated in winter, but a residual cultivation pan limited the effect of the mole drains in 1978–9. In 1979–80, after disrupting the pan, the water table in the moledrained plots was about 25 cm deeper than in the undrained plots, root growth was greater and yield of winter wheat 11% heavier. About 90% of water and nutrients draining from the drained plots were carried in the mole and pipe system. The results on water balance, nutrient losses, crop growth and yield are fully reported in companion papers (Harris et al. 1984; Ellis et al. 1984).

Description: SummaryIndividual muscles, individual bones and fat depots from the non-carcass parts (head, foreshanks and tail) of 40 steers (chilled carcass weight 142–174 kg) were studied in an attempt to predict carcass composition more accurately than in an earlier study where the crude non-carcass parts, head, tongue, foreshanks and hindshanks were used.The technique did not improve the accuracy of prediction of muscle or bone. Carcass fat, which was calculated by difference in the earlier study, was predicted more accurately using intermandibular fat weight (requiring 3–4 min to obtain) plus fat thickness at the 12th rib. However, the accuracy of this prediction (carcass fatness range 14·0–33·6%, residual standard deviation 1·98%) was no greater than that using chilled side weight plus fat thickness at the 12th rib.Careful dissection and trimming of anatomical entities from the non-carcass parts therefore offered a slight advantage only in the prediction of carcass components over existing techniques.Substitution of hot side weight for chilled side weight, and sacral crest fat thickness for fat thickness at the 12th rib did not lead to a loss in the accuracy of prediction of muscle, bone or fat.

Description: Underground irrigation water, particularly saline, when in arid and semi-arid regions of India may contain toxic amounts of B, from a trace up to 10 mg B/l (Anon. 1981–82). Continuous use of such water for irrigation may lead to the accumulation of salts and B in soil and this creates toxicity problems. Kanwar & Mehta (1970) have reported that water containing 2 mg B/l is hazardous if used on heavy soils. For sandy loam soils of semi-arid tracts in India, Chauhan & Powar (1978) have reported reductions in the grain yield of wheat and pea at 4 and 6 mg B/l respectively, while under similar conditions grain yield of lentil and barley was reduced at 3 and 6 mg B/l respectively (Chauhan & Asthana, 1981). So far, few attempts have been made to evaluate the effect of boronated saline water on soil and crops, under different agroclimatic conditions. A study of the effect of boronated saline water on an important oil-seed crop, linseed, on alkaline sandy loam soil in the semi-arid region of Agra, India was therefore undertaken.

Description: SummaryVigorous cauliflower plants sometimes bear abnormally small curds, yet this common problem has received little recognition or attention from research workers. Curd size is often reduced towards the end of the harvesting period of a crop, and this is more marked if environmental conditions reduce mean curd size and lengthen the time to maturity. Small late curds may be a consequence of their slow growth rather than their late initiation. Cultivars differ in their tendency to produce plants with late maturity and small curds. This may not be due to genetic differences within cultivars. Moreover, breeding to eliminate or reduce this condition may not be possible without affecting overall maturity time and curd size.

Description: SummaryThe development of spring and winter barley sown in both the spring and autumn has been followed in two seasons. The rates of development were similar in both types for autumn sowings but the spring types developed faster in spring sowings. Differences in the rate of development were related to photoperiod and temperature although soil water stress modified variety response. Yields were higher from autumn and early spring sowings. Sowing in April resulted in a considerable reduction in yield. The significance of these results for barley breeders is discussed.

Description: SummaryIn a 2-year field study conducted at Lucknow (26·5° N, 80·5° E and 120 m altitude), plant height, leaf area index, dry-matter accumulation and N uptake of opium poppy (Papaver somniferum L.) followed a sigmoid path. After attaining a peak of accumulation at 120 days, dry matter declined in plots given N fertilizer but remained static in the control. N application (50, 100, 150 and 200 kg/ha) increased the opium, seed and morphine yields compared with the control. Morphine concentration (%) in the opium, however, increased up to 100 kg N/ha and decreased when N doses exceeded that level. Divided application of N, i.e. half at sowing and remainder at the stem elongation stage, proved beneficial for opium, seed and morphine yields.

Description: SummaryA simple technique to evaluate accurately the effect of mechanical stress on root growth has been developed. The roots are allowed to grow against a predetermined pressure in the chamber of a pressure-plate apparatus. The root growth was studied against the applied pressures of 0, 2, 4, 6, 8 and 10 bar. A relationship of the form Y = aXb was observed between the rate of root elongation (Y) and applied pressure (X).

Description: It is well known that the uptake of fertilizer-N by crops is relatively inefficient, often amounting to less than half the quantity applied. Some becomes unavailable by combining with soil organic matter and some is lost from the system by surface runoff, leaching, denitriiication or ammonia volatilization. Most research has shown urea to be less effective than other sources of N when applied under conditions where ammonia volatilization becomes significant, especially when broadcast on the surface of alkaline and calcareous soils. Devine & Holmes (1964) found that ammonium sulphate was less effective than ammonium nitrate for wheat on a calcareous soil. Nitrogen recovery by wheat and barley tended to be similar for various N-fertilizers but further recovery in the following year was highest from calcium nitrate followed by ammonium sulphate and ammonium nitrate (Alessi & Power, 1973). On the other hand the efficiency of nitrate-N for flooded rice is less than that of ammoniacal fertilizers, owing to denitrification and leaching. Sarkar et al. (1978) found that rice grain yields with ammonium sulphate were significantly higher than with urea whereas Narain & Datta (1974) reported that urea and ammonium sulphate were equivalent and gave significantly higher yields of rice than ammonium nitrate. Therefore, yield responses to different sources of N vary depending upon soil, crop, climate and management factors; the study reported here was initiated to provide information on the relative performance of various N carriers applied to wheat and rice in the Punjab.

Description: SummaryPlants of the Cucurbita pepo L. cultivars Cinderella, Cobham Bush Green and Gold-rush were inoculated with six strains of cucumber mosaic virus (CMV) from different geographical areas and known to differ in pathogenicity and virulence. The cv. Cinderella showed high resistance to all strains, cv. Cobham Bush Green was moderately resistant and cv. Goldrush was highly susceptible particularly to the CMV–SEV strain which caused necrotic symptoms.

Description: SummaryTo ascertain the inheritance of seed shape and resistance to Ascochyta blight and to incorporate resistance in commercial cultivars, crosses were made between cv. Kinnauri, a round-seeded resistant source and commercially important cvs Bonneville, Lincoln, GC 141, and Selection 18, highly susceptible to disease but wrinkled-seeded. The F1, F2 and F3 data indicated that seed shape and resistance to Ascochyta blight is determined by two independently inherited genes. Round seed and disease resistance are dominant over wrinkled seed and susceptibility. Commercially desirable lines have been selected which combine the resistance gene of Kinnauri with wrinkled seed from susceptible commercial cultivars, and which also possess high pod yields and other desirable characters.

Description: SummaryHeterosis and combining abilities for yield, bollworm resistance, fruiting efficiency and photosynthesis were studied in a five-parent diallel involving cotton (Gossypium hirsutum) strains differing in their resistance to the bollworm complex (Heliothis zea and H. virescens).Substantial magnitudes of useful heterosis (over the commercial cultivar ‘Coker 304’) were observed for yield and other agronomic characters. Useful heterosis for yield ranged from 1 to 32·7%. The highest yielding hybrid was Coker 304 × PD 695. The strain PD 695 is moderately resistant to bollworms.All the hybrids having at least one resistant strain as their parent suffered less damage from bollworms than Coker 304. The resistant strains (BW 76–31, PD 695 andred leaf cotton) had desirable general combining ability (GCA) effects for bollworm damage. Relative yield (yield without protection expressed as percentage of yield with protection) was used as a measure of bollworm resistance. The high gossypol strain BW 76–31 had desirable GCA effects for relative yield, bollworm damage to buds, number of live worms and for bolls per plant. The fruiting efficiencies and photosynthetic rates of some bollworm-resistant strains were similar to those of a high-yielding, moderately susceptible cultivar.Combining-ability analysis indicated BW 76–31 to be a desirable parent for use in hybridization programmes for improving agronomic performance, fruiting efficiency, photosynthetic rate and bollworm resistance. It was also observed that bollworm-resistant cottons do not always have lower fruiting efficiencies and photosynthetic rates and it might be possible to combine this resistance with high yields.

Description: SUMMARYRoot growth is considered in relation to shoot growth for high-yielding crops of winter wheat grown on three soil types in 1980 and 1981. From the time that nitrogen was applied to anthesis, shoot growth was rapid and effectively linear in relation to thermal time, whereas root growth entered a rapid linear phase after about 500–600 °C days, well before the application of nitrogen. Between double ridges and anthesis, shoots accumulated dry matter 10 times faster than roots on average. The relationship between root and shoot growth was different in the two years, which was probably due to reduced assimilate production in 1981 as a result of the dull, cloudy weather. At anthesis, average root: plant ratios for 1980 and 1981 were 0·132 and 0·093 respectively but no significant differences were caused by sowing dates or sites, despite the presence of a plough-pan on one of the soils.Root:plant ratios declined from about 0·4 in winter and early spring to about 0·1 by anthesis. There was considerable variability in root:plant ratios for different crops during winter and early spring, caused in part by differences in soil-N availability and timing of application of fertilizer nitrogen.

Description: SUMMARYSix experiments which compared a range of contrasting varieties are reported. Two experiments were at a very early, coastal site in N. Pembrokeshire (Trefin), two at a site in South Pembrokeshire (Trefloyne) and two at a coastal site in N. Norfolk (Brancaster). No variety was in every experiment but several were in the majority of experiments. In some experiments sprout growth was manipulated by control of storage temperatures. A variety classified as early or second early produced the highest yields in all experiments but the yields of the best maincrop varieties were high and substantially better than many early varieties. The highest-yielding variety at the first harvest maintained this advantage throughout June and July. At two sites (Trefin and Brancaster) the highest-yielding variety was consistent from year to year but overall the ranking order of varieties for yields was inconsistent, e.g. Arran Comet was the highest-yielding variety at Trefin in both years and one of the lowest yielding at Brancaster.The results suggest that it is unwise to attempt to rank varieties for early yields by an overall score. The maturity classification of varieties is not necessarily an accurate guide to the utility of a variety. A consideration of the physiological age of the seed and growing conditions provided some explanation of these effects and their implication for breeding are discussed.

Description: SUMMARYFour trials were carried out to investigate the effect of inter-plot competition on seed yield and plant height of field beans using experimental designs balanced for neighbours. One trial tested four varieties ranging in final height from 25 to 100 cm and sown in four-row plots with 30 cm spacing between rows and one blank row between plots. When grown between plots of a dwarf variety, the plot yield of the tallest variety was increased by 20% compared with its pure stand yield: a complementary reduction in yield was shown by the dwarf variety when grown between plots of the tall. The effect on the yield of the inner rows of the plot was somewhat smaller than that of the outer rows but still significant. Another trial with six commercial varieties differing in final height by less than 15 cm showed no differential effects of inter-varietal competition on yield. In two trials with six varieties of widely differing heights planted with 50 cm spacing between rows, but no gap between plots, plot yield was strongly affected by the neighbouring variety in the trial with single-row plots, while yields from the four-row trial showed a large interaction between variety and inner and outer row position, again indicative of inter-variety competition. The yield response to competition could be described by a common linear regression on the excess height of plot neighbours: there was little evidence of varietal differences in sensitivity or aggressiveness.Plant height showed a positive response to height of plot neighbours in all four trials, whilst in the single-row trial, the ratio of grain yield to total dry-matter production (harvest index) was negatively related to excess height of neighbours.The results suggest that, when testing varieties differing in height by more than 20 cm, at least two buffer rows, e.g. six-row plots with the centre two rows harvested, are required to obtain a true comparison of pure-stand yield. Alternatively, when this procedure would result in an unacceptable use of resources, one of the statistical models adapted in this paper may be used to adjust variety yields for pure stands.

Description: SummaryTwo experiments were conducted with milking cows on continuously stocked perennial ryegrass pastures. In each a control group, T0, received 1 kg/day of a concentrate supplement and treatment groups T1 and T2 received 4 kg (Expt 1) or 5 kg/day (Expt 2) of a low quality T1 or a high quality T2 concentrate. In Expt 1 treatments were applied continuously for 14 weeks to a total of 30 cows. In Expt 2 a Latin square design for 9 weeks was conducted with 18 cows. The stocking rate of the pasture declined from 9·6 to 5·1 cows per ha (mean 6·7 cows/ha) from May to August (Expt 1) and was maintained at 3 cows/ha in August-October (Expt 2).Supplements increased total intakes by 0·92 and 0·77 kg organic matter (OM)/kg OM supplied in the concentrates respectively for Expts 1 and 2. Milk yields increased by 0·6 and 0·5 kg/kg concentrate supplied and supplemented cows showed small increases in live weight. Differences in lactation milk yield just approached significance. Grazing times were only slightly reduced by supplements and bite sizes were lower than normal. There was no important difference in animal performance between the two concentrates. The total output from the pasture was 19·6t milk and 115 GJ of utilized metabolizable energy per hectare.Reasons for the high supplementary effect of the concentrates and its implications for stocking rates are discussed.

Description: SummaryAn approximate analytical method derived by Wilson & Gelhar (1981) is a powerful and flexible one for calculating solute distribution profiles developing under steady state and transient water flow conditions. Solute concentration profiles developing from an initial deposition in the surface layer, as the soil profile returns to field capacity, have been calculated using the method for idealized representations of the two principal forms of water redistribution.The profiles depend very strongly on the mode of redistribution of the water. However, the small spread of the final profiles (at field capacity) across the range of water redistribution types examined suggest that, for agricultural application, it might be accurate enough to use a simplified representation of the actual redistribution rather than the correct, and inevitably more complicated, water flows and distribution.

Description: SummaryCalves from three breeds, Brahman, Hereford × Shorthorn (HS) and Brahman × HS (BX), were divided equally into two groups, one of which was treated every 3 weeks from birth onwards to control ticks and gastrointestinal helminths, and one of which was untreated. Mortalities, growth rates and levels of resistance to environmental stresses that affected both mortality and growth under grazing conditions were recorded for all animals up to weaning (6 months) and for all males up to 15 months of age. The Brahmans were the most and the HS were the least resistant to environmental stresses, each of which was shown to depress growth in proportion to its magnitude and to contribute to the high mortalities of the HS. All breeds responded positively to parasite control with the greatest response in both survival and growth in the HS breed and the least response in the Brahman breed.Samples of males from the various breed-treatment groups were taken into pens where they were protected from environmental stresses and fed both low-quality pasture hay and high-quality lucerne hay ad libitum. Measurements were made of fasting metabolism, maintenance requirement, voluntary food intake and gain, variables related to the growth potential of each animal. The HS animals had the highest whilst the Brahmans had the lowest values for each variable.However, despite their low growth potential, the Brahmans had the highest growtli rate, and the HS, despite their high growth potential, had the lowest growth rate, when growth was measured in the presence of all environmental stresses. When parasites were controlled, growth rates were highest for the BX, the breed with intermediate growtli potential, and did not differ between the HS and Brahmans. These interactions arose because of the different contributions of resistance to environmental stresses and growth potential to growth rate measured at the different levels of environmental stresses. The relevance of these interactions to breed evaluation and cross-breeding is considered.Growth potential and resistance to environmental stresses were negatively correlated both between and within breeds, though the latter was biased by the effects of compensation. The influence of these relationships on the likely outcome of selection for increased growth rate, both between and within breeds, is discussed.

Description: SummaryEffects of three levels of N application and four intervals between harvests on field swards of perennial ryegrass (Lolium perenne L.) were studied during 6-week periods in summer and spring. Ryegrass was compared with tall fescue (Festuca arundinacea Schreb.) in spring and autumn.An increase in the interval between harvests from 1 to 6 weeks allowed a larger, positive response to applied N to develop in respect of dry-matter yield, weight per tiller, and leaf blade and sheath length. Response to N was expressed more in terms of larger leaf blades than in a larger number of tillers. Tall fescue leaf blade size was increased more than that of ryegrass by a period of uninterrupted growth in May.Within 1 week of its application, N had increased the N content of both emerging and dying leaf blades and had increased the width and reduced the weight per unit area of the emerging blades. The positive effect of N on blade width (and on blade length where uninterrupted growth was allowed) and its negative effect on weight per unit area were ‘carried through’ the sward, to be recorded a second time when that generation of blades had become the dying blades.Applied N increased the number of tillers, the rate of emergence of new tillers, the proportion of tiller buds which developed into tillers, and the proportion of relatively young tiller buds which developed.

Description: SummaryWorking rules for determining plot size and number of plots within a block in field experiments are proposed based on the value of the intrablock correlation (ρ), which can be obtained from the analysis of variance of a randomized-block experiment. The method uses Binns' (1982) equation to relate this correlation to Smith's (1938) empirical law. The rules are: (1) if ρ is greater than 0·5, use an incomplete block design or reduce the plot size in order to increase the number of replications; (2) if ρ is less than 0·1, an increase in plot size is effective; (3) if ρ is between 0·1 and 0·5, an increase in plot size and a decrease in the number of plots per block may be helpful in combination.

Description: SummaryA field experiment was made on rice during the rainy seasons of 1982 and 1983 to study the relative efficiency of prilled urea and urea super granules (USG) applied broadcast or deep placed at different times. USG gave more, longer and heavier panicles with a higher percentage of filled grains than prilled urea. Deep placement of 60 kg N/ha as USG in two applications (half 10 days after transplanting and half at panicle initiation) gave the same grain yield as 120 kg N/ha of prilled urea applied half at final puddling and half at panicle initiation. Urea super granules, therefore, hold considerable promise as a nitrogen fertilizer for rice.

Description: SummaryOestrous activity of three flocks of Ossimi, subtropical fat-tailed ewes was detected by teaser rams over a calendar year. The flocks were raised at north Delta, mid-Delta and middle Egypt.The two Delta flocks showed irregularity in percentage of ewes coming into oestrus monthly, with a marked decrease in March, April and May, April being the lowest. On the other hand, the mid-Egypt flock showed consistent oestrous activity throughout the year, with small fluctuations.The three flocks showed month-to-month variation in incidence of oestrus per ewe, with lower activity in the spring months. Neither of the two Delta flocks showed real regular oestrous activity in any month throughout the year, with high ewe variation. Some ewes showed regular activity throughout the year (16–20 cycles), whereas some others showed only 4–7 cycles per year.There were two periods of the year with high frequency of anoestrus. The more intense was March–May while fewer ewes had an anoestrous period in July–August. This was the case in the three flocks but with varying intensity.A period of more than 1 year of detecting oestrus affected oestrous performance of the ewes and should be avoided.

Description: SummaryMetal contents are reported of the soils from a field experiment in which two rates of various organic manures, including sewage sludge and sludge compost, were applied from 1942 to 1961. Changes in the concentrations of some elements in the sludges during the 20 years are also presented.The percentage recoveries of the added metals Zn, Cu, Ni, Pb, Cd and Cr in the topsoil varied from 71 to 96%. In 1960, extractability of the metals from the soils by 0·05 M-EDTA was 50% of the aqua regia-soluble total metals. This figure did not vary greatly with metal or with the type of organic manure that was applied.

Description: SUMMARYThe efficiency of visual selection in a glasshouse of 1600 seedlings compared with visual selection in the field of the same clones is examined. Also the amount of agreement in assessment between four different potato breeders screening the same clones is investigated. Seedlings were grown from true seed in four-inch pots in a glasshouse and all the clones which produced tubers were grown in the field the following year. Clones which produced more than one tuber from a seedling were grown at two locations in the first clonal year. One of the sites used in the first clonal year is normally used for potato yield trials (i.e. a ware site) and the other is normally used for the production of healthy seed tubers (i.e. a seed site). In all three environments, the tubers produced from each plant were assessed by four breeders independently on a 1–9 scale of increasing attractiveness.From the data it was found that the repeatability of assessment between the glasshouse and the first clonal year was low in that the correlation between the average preference score of the four breeders in the glasshouse and each of the two first clonal year sites accounted for only 8·24 and 6·84% of the total variation. Many clones which had low scores in the glasshouse were subsequently given high scores in the first clonal year. It was therefore concluded that selection of seedlings was not very efficient. Although, in general, the weight of the tuber that was planted greatly influenced whether a clone was selected in the first clonal year, a large number of clones which produced only small tubers in the glasshouse were subsequently selected in the first clonal year.Within each environment the four breeders were either all selecting, or all rejecting, a much higher proportion of clones than would be expected if selection had been made completely at random. The breeders were in most agreement when assessing clones at the ‘ware’ site, and in most disagreement when assessing them grown in the glasshouse from true seed. Therefore the poor efficiency of selection of seedlings grown in the glasshouse was not, in the main, a result of a high error variance in visual assessment but rather due to poor association between the performance of seedlings and first clonal year plants.

Description: SUMMARYExperiments were conducted over two cropping seasons at the Sugar Cane Estate of the Nigerian Sugar Company, Bacita, Nigeria to determine the effectiveness of additional nitrogen fertilizer, chemical sprays and delayed planting in controlling flowering in two commercial sugar-cane varieties (Co. 1001 andCp. 29/116). Application of 150 and 250 kg N/ha, 8 weeks before initiation, reduced flowering in Co. 1001 by up to 13·5 and 11 % respectively. Flowering was as low as 2% in some of the above treatments while the average flowering in plots with no additional nitrogen application was more than 80%. imilarly, application of diuron (4·0 kg/ha) and paraquat (0'5 kg/ha) to the top leaves (3 weeks before initiation) of Co. 1001 reduced flowering in this variety up to 45 and 35% respectively. Neither the application of diuron and paraquat nor additional nitrogen fertilizer sufficiently reduced flowering in Cp. 29/116. The time of planting affected flowering. Over 85% flowering was observed in November 1982 from Co. 1001 fields planted in January 1982 (10 months before initiation time). However, fields of the same variety planted in June 1982 (4 months before initiation time) did not show any initiation until harvest in May 1983. The implications of the above results are discussed.

Description: SummaryThree experiments were carried out in which nitrogen was applied to spring barley (cv. Midas) either all in the seed bed or as a divided dressing with 10 or 25 kg/ha in the seed bed and 50 or 60 kg applied at emergence or 10, 20, 30, 40, 50, 60 or 70 days after emergence. Applying part of the nitrogen as a top dressing up to 30 days after emergence and 50 days after emergence had no significant effects on the grain and straw yields respectively, compared with applying all the nitrogen in the seed bed. Grain yields were progressively reduced with top dressings from 40 days after emergence (first node stage) onwards. Applications at 60 or 70 days did not give more grain yield than the no-nitrogen control, but gave straw yields which were intermediate between the no-nitrogen and seed-bed nitrogen treatments. Top dressing at 40 days after emergence stimulated tiller survival but did not improve grain yield because there were fewer grains per ear. Thousand-grain weights were lowest with top dressings at 50 days after emergence and grain nitrogen increased progressively with delay in top dressings from 30 days after emergence onwards.

Description: SummarySeven out of ten chemical extractants were found to be promising for the evaluation of critical limit and response of wheat grown in pots to Cu application in Sub-Himalayan hill and forest soils of recent alluvium origin. The critical limit of available Cu using DTPA-CaCl2(pH 7·3), DTPA-NH4HCO3 (pH 7·6), EDTA-(NH4)2CO3 of pH 8·6, EDTANH4OAc (pH 7·0), n-NH4OAC (pH 7·0), n-NH4OAC (pH 4·8) and n-Mg(NO3)2 of pH 5·9, was 0·66, 1·73, 1·95, 1·38, 0·13, 0·20 and 0·47 mg Cu/kg, respectively. The amount of Cu extracted by these extractants was positively and significantly correlated with ‘Bray's percent yield’. Apart from ‘Bray's per cent yield’, the Cu extracted by most of these extractants was positively and significantly correlated with Cu concentration in the third leaf of wheat, Cu uptake by wheat shoots and organic carbon content of the soils, and negatively correlated with soil pH but the value of this relationship did not approach the 5% level of significance. n-Mg(NO3)2 of pH6·7, N-NH4NO3 and 0·1 n-HCl were found to be ineffective extractants. Among chelating agents, DTPA-CaCl2 was found to be most and EDTA-NH4OAc least promising extractant. N-NH4OAC (pH 4·8) proved to be better than N-NH4OAC (pH 7·0). The critical Cu concentration in the third leaf of wheat was 8·8 mg Cu/kg, below which responses in dry weight to Cu application may be expected.

Description: SummaryThe soil water regimes, flow paths of water and concentrations of nutrients in this water were measured for a clay soil growing winter wheat in 1978–9 and 1979–80. The soil was either drained with mole drains at 2 m spacing connected to plot drains 46 m apart or undrained. In the 1st year a compacted layer at about 20 cm depth caused a perched water table in the Ap horizon in both drainage treatments, and prevented the mole drains at 60 cm from affecting the water table. In 1979–80 after cultivation to disrupt the compacted layer, midway between the mole drains the depth to the winter water table was 20 cm greater than in undrained soil.Surface flow, interflow at the depth of the plough layer and deep drainflow from mole and pipe drains responded rapidly to winter rainfall events. During both winters the mole and tile system removed most of the rainfall on the drained plots and the peaky hydrographs were typical of a mole system in a clay soil. In the undrained plots only a small proportion of the winter rainfall was accounted for in flow from the top 30 cm, and up to 75% of the water was able to percolate downwards possibly to below the barriers that separated the plots. Long-term water-balance studies indicated that a proportion of the water moving to depth in the undrained plots was probably entering the deep drainage system of the drained plots. As a result, the mole and pipe drainage system often removed more water than the rainfall input less evapotranspiration. This problem did not affect the depth to the water tables.For each flow component concentrations of nitrate, ammonium, nitrous oxide, phosphorus, potassium and calcium were measured in the drainage water. Concentrations of nitrate-N from all drained plots were largest in autumn, being in the range 50–95 mg N/1, but then decreased to 1–5 mg N/1 by the end of March. Losses of nitrate-N were mainly through the mole drains and amounted to 43·6 and 59·7 kg N/ha in the 2 years. The quantities of nitrate-N lost in surface runoff or in flow in the cultivated layer were small on both treatments. Gaseous nitrous oxide, ammonium and phosphorus contents were very small. Potassium concentrations were somewhat larger, but not exceeding 3·5 mg/1. The calcium concentrations were in the range 40–210 mg/1. Concentrations of herbicides measured in November 1980 were negligible.In the 2nd year water was taken up from a greater depth in the drained than in the undrained plots from April onwards. These results are discussed in relation to water supply to the crops at this site.

Description: SummaryAzospirillum brasilense was treated with nitrosoguanidine and five drug-resistant mutant strains isolated. The effects of acriflavin on pre- and post-irradiation with u.v. light and the level of antibiotic resistance were studied. Variations in factors were found between the strains. Inoculation of finger millet with A. brasilense and mutant strains led to significant increases in grain yield and nitrogenase activity compared with the uninoculated control, with significant strain x genotype interactions. Differential response of genotype and strain was noted on the protein and amino acid concentration of seeds.

Description: SummaryA missing value technique for the analysis of data where repeated measurements are taken on each experimental unit is proposed. The method suggested, which is a natural multivariate analogue of the well-known technique for univariate analyses, fits those missing values which minimize the determinant of the sums of squares and products matrix and provides the necessary downward adjustment to the residual degrees of freedom. A simulation exercise provides evidence that the method is fairly reliable.

Description: SummaryThis paper provides estimates of varieties × environments and plot error variances based on more than 1000 trials of varieties of oats, barley, wheat, perennial and Italian ryegrass, timothy, cocksfoot, potato, sugar beet, swedes, autumn kale, forage maize and field beans. Tables of critical differences and acceptance probabilities are presented to guide in planning future series of trials.

Description: SummaryThree cutting stages, the boot stage, 50% heading and the milk stage of grain, were imposed on eight barley varieties at four sites, two in each of two successive cropping seasons. Dry-matter and digestible yield increased significantly when harvest was delayed from the boot to the milk stage but crude-protein content and digestibility declined with advanced maturity. A similar pattern of response was obtained in most cases when varieties were examined individually. Variety 628 produced the highest yield, 8·34 t D.M./ha, while the most digestible variety was Athenais with 61·9% digestibility. In low-rainfall regions harvesting at the later stages of maturity is recommended, to take advantage of the higher D.M. yields.

Description: SummaryLive-weight gain of beef cattle grazing all-grass or grass-clover pastures, details of which have been reported previously, was significantly (P 〈 0·01) correlated with pasture growth rate, but not with pasture dry matter on offer (either total or green), or with dietary-energy concentration. From ideas generated from the relationship between live-weight gain and pasture growth rate, and using intake values measured from the number and size of prehension bites, it is shown how high live-weight gain for measured dietary-energy concentration could be explained by differential contribution to digestibility and voluntary intake from pasture new growth.

Description: SummaryThe persistence under a close intermittent grazing regime of eight accessions of Stylosanthes guianensis, Stylosanthes macrocephala and Stylosanthes capitata in combination with Andropogon gayanus (cv. Planaltina) and Brachiaria decumbens (cv. Basilisk) was evaluated in small plots on a low fertility acid oxisol in the tropical savannah region of Brazil. Five accessions persisted for four seasons with both grasses, although legume yields were lower in the B. decumbens associations.S. macrocephala CIAT 1582 (CPAC 139), S. capitata CIAT 1019 (CPAC 704) and CIAT 1097 (CPAC 706) were the most productive accessions at the end of the experiment. The three accessions S. guianensis cv. Cook, S. capitata CIAT 1315 (CPAC 707) and CIAT 1405 (CPAC 846), which failed to persist, were destroyed by anthracnose (Colletotrichum gloeosporioides). This disease remains the primary factor limiting the use of Stylosanthes in the region. The value of small-plot grazing experiments is briefly discussed.

Description: SummaryThe seedling emergence from fluid-drilled germinating and natural onion seeds was compared at five sowing dates between 10 February and 18 May on irrigated and unirrigated plots in two experiments. In the second experiment fluid-drilled seeds selected for uniform germination were also included. There were few significant differences between the emergence of seedlings from germinating and natural seeds in the field sowings of Expt 1. However, a reduction in mean emergence time at the earliest sowing led to an increase in bulb weight while a reduction in the spread of emergence at sowing 3 led to a reduced coefficient of variation of bulb diameter at harvest. Under the less variable conditions on the irrigated plots of Expt 2 germinating seeds reduced mean emergence time and increased percentage emergence compared with natural seed at some sowings. Fluid-drilled selected germinated seeds, however, reduced mean emergence time and increased percentage emergence at every sowing and reduced the spread of emergence at all but the first sowing compared with natural seed.Low soil moisture content made seedling emergence more unpredictable and reduced the benefits gained by sowing germinated seeds. The results presented suggest that techniques to increase the proportion of germinated seeds at the point of sowing and economical methods of applying water during periods of low soil moisture following sowing are needed if the full benefits of fluid drilling are to be realized.

Description: SummaryIsogenic fertile and sterile forage maize (cv. LG 11) grown in separate fields were harvested at regular intervals during growth between mid-July and early October 1979. Leaf, stem and ear components and whole plant (before and after ensiling) were examined for changes in the concentration of dry matter (D.M.), soluble sugars, starch, hemicellulose, cellulose, neutral detergent fibre (NDF) and acid detergent fibre (ADF). In vitro digestibility values for D.M., organic matter (OM) and OM in the D.M. were also determined in fresh and ensiled whole crops.Prior to ensiling the concentration of non-structural carbohydrates in the two crops was markedly different. Fresh fertile plants contained (as g/kg D.M.) 369 and 101 of starch and soluble sugars respectively. Corresponding values for sterile plants were 54 and 343 respectively. Sucrose was the most abundant soluble sugar present and contributed 64 and 74% of the totals in fertile and sterile plants respectively, prior to ensiling. Increases in plant D.M. during growth were significantly affected by the deposition of starch and are described by the following equation:y = 13·6 + 0·49 (±0·073) x(r = 0·93)where y = whole-crop D.M. concentration and x = starch concentration in D.M. The concentrations of hemicellulose and cellulose of both types of fresh plants were similar but those of ADF and NDF were lower in sterile plants. Xylose was the major constituent neutral sugar in the hemicellulose fraction and formed 68 and 76% of the total hemicellulose in the fertile and sterile plants, respectively. In vitro digestibility values of sterile plants tended to be higher than their fertile counterparts.After ensiling, the concentration of soluble sugar in the sterile and fertile crops decreased from 343 to 8 g/kg D.M. and 101 to 5 g/kg D.M. respectively. The in vitro DOMD values of the sterile and fertile crops decreased by 16 and 11 percentage units respectively; both final values were recorded as 61.In vivo digestibility values determined in 18-month-old wether sheep fed at maintenance, for NDF, ADF, cellulose, hemicellulose, nitrogen, OM, D.M. and OM in D.M. were 60·2, 58·0, 65·8, 64·1, 32·9, 66·6, 65·4 and 63·7 respectively for fertile plant silage. These were all markedly lower than the corresponding values for the sterile plant silage which were 68·3, 70·3, 74·8, 73·3, 60·3, 71·3, 69·6 and 67·7 respectively. Within the hemicellulose fraction the digestibility values for xylose in both sterile and fertile plant silage were considerably lower than the values recorded for either arabinose or galactose. In vitro digestibility values for D.M., OM and OM in the D.M. were similar to in vivo values for fertile plant silage but were lower than in vivo values for sterile plant silage.Dairy herd replacement heifers (aged 3–6 months) had higher D.M. intakes when given fertile plant silage ad libitum than with sterile plant silage. However, the liveweight gains of the heifers on sterile and fertile plant silage differed little.

Description: SummaryWhen pre-harvest foliar applications of growth regulators were made to vines of Dioscorea esculenta cv. Chinese Yam and D. alata cv. White Lisbon there were no obvious effects on tubers of D. alata, but dramatic effects on tuber development, storage and germination were obtained with D. esculenta tubers. Gibberellic acid caused marked extensions in tuber dormancy, 2,4-dichlorophenoxyacetic acid resulted in marked callus development, delayed germination and abnormal shoot and root development and indole acetic acid resulted in fingering of the tubers. It was concluded that there was potential for commercial exploitation of pre-harvest gibberellic acid treatments in extension of dormancy in Chinese Yam tubers and that the lack of response of D. alata tubers to foliar application of growth regulators warranted further investigation.

Description: SummarySoil water content affected the nodulation and N2 fixation of Phaseolus vulgaris by Rhizobium phaseoli and the utilization of mineral N by plants. Plants grown in wet soil produced twice as much as those grown on dry soils. Nodule weight and activity were five to ten times greater than those from dry soils. At 45 days, N additions inhibited nodulation, but this effect was partially diminished in wet soils.The maximum N utilization from fertilizer to produce dry matter did not correspond to maximum N utilization by pods.

Description: SummaryThe effects of post-harvest application of gibberellic acid on dormancy of tubers of Dioscorea alata and D. esculenta were examined. In both species, gibberellic acid extended the dormancy of immature and mature tubers but when GA3 application was made after storage for varying lengths of time, there was a decreasing effect with increased storage time. Dormancy was also reinduced in germinating tubers, that had gone through a normal dormant period, as a result of gibberellic acid treatment. A possible mechanism of dormancy in tropical yams is discussed. It is concluded that use of gibberellic acid as a means of extending the storage life of yam tubers by post-harvest application is a distinct possibility.

Description: SummaryChemical compositional (protein, fat, ash and water) changes in the fleece-free empty body, carcass, viscera and ‘remainder’ components of Corriedale wether sheep were measured by serial slaughter of animals following five different growth paths.The composition of sheep, after losing up to 34% of body weight over 18 weeks at 125 g/day, was significantly different from a continuously growing control group at the same body weight, but the actual differences in the weights of tissues were small. At the end of weight loss all treatment sheep contained more fat and protein, and less water than controls.The different growth paths followed during weight loss led to differences in the proportions of protein, fat, ash and water lost and to differences between the three body components in the relative contribution made by each.The periods of weight loss led to changes in the relative growth coefficients for chemical constituents during realimentation, particularly those of fat and ash which were reduced, and of water which was increased.The response to realimentation differed between body components, particularly the carcass and viscera. Above the body weight at which weight loss was imposed the realimented sheep did not differ in chemical composition from the continuously ad libitum fed controls when compared at the same weight.

Description: SummaryEvaluation of some insecticides against nine strains of S. littoralis, selected with decamethrin and foliar fertilizers separately and their combinations for three successive generations, was conducted to elucidate the effects of fertilizers on the tolerance pattern. The results indicate that the selection with fertilizers induced a low level of tolerance to both cyolane and profenofos. The LC50 of chlorpyrifos for all fertilizers' strains was lower than that of the susceptible strain. The efficiency of cyolane and fenvalerate on strains developed by the selection with decamethrin-fertilizer combinations was remarkably increased. Since the selection with fertilizers has induced a tolerance to some insecticides such as cyolane and profenofos and as the efficiency of these insecticides was enhanced on strains developed by the pressure of decamethrinfertilizer combinations, it is preferable to use decamethrin simultaneously in admixture with foliar fertilizers for pest control.

Description: SummaryThree groups of red deer hinds of 9–10 years of age were grazed upon an indigenous hill pasture (A), an improved species grass sward (predominantly perennial ryegrass) maintained at 〈 1500 kg D.M./ha (B), and one maintained at 2000 kg D.M./ha (C) from immediately after calving on 29 May until weaning on 22 September. Numbers of hinds in each treatment were 8, 6 and 9 respectively. Milk yields of hinds were estimated on swards A and C by the calf-suckling technique and hind and calf live-weight changes and hind grazing behaviour were recorded on all three swards during lactation.Hinds on award C yielded on average 60% more milk over the lactation period than hinds on sward A, day 40 yields being 2·2 and 1·5 kg/day respectively. Calf growth rates (treatment A, 257 ± 9·5, B, 324 ± 12·1 and C, 369 ± 14·5 g/day) were higher on the improved species sward than on the hill sward and higher on the improved sward with the greater herbage mass. On treatments A and C calf growth rates were significantly (P 〈 0·05, r = 0·69) correlated with milk yield throughout lactation. At weaning, calves on sward C were 7·5 and 4·5 kg heavier than those on swards A and B respectively. Biting rates were lower (33 v. 56 bites/min) and grazing times higher (11.7 v. 6.0 h) on sward A than swards B and C. The poorer performance of hinds and their calves on sward A was considered to be due to a lower quality of diet ingested, and to behavioural limitations on intake occurring when hinds graze indigenous swards of relatively high species diversity. These results are discussed in relation to the grazing behaviour of cattle and sheep on similar swards.The significance of the results to red deer farming in the U.K. is briefly discussed.

Description: SummaryMost commercial cultivars of Cucurbita pepo L. reacted by producing severe leaf symptoms when infected with either of two British strains of cucumber mosaic virus. Resistance was identified in some pumpkin-types of C. pepo, with the highest level in cv. Cinderella. Studies with selfed populations produced from selected resistant plants demonstrated that resistance in cv. Cinderella is heritable.

Description: SummaryOne hundred and twelve indigenous gilts and sows were used in two trials to study the effects of strepcillin (a mixture of streptomycin and penicillin) at 0, 25, 50, 75 and 100 g/t feed in a basal 15% protein diet and strepcillin at 0, 25, and 50g/t feed in rations containing 12, 15 and 18% protein, on the reproductive performance of pigs.Reproductive performance in terms of sow net gain in weight through the reproductive cycle, average birth weight of live pigs per litter and number of pigs weaned per litter were significantly affected by antibiotic levels. The dietary level of 50 g antibiotic/t feed gave the highest reproductive performance though at higher levels no adverse effects on reproductive performance were obtained.Reproductive performance of pigs was significantly influenced by protein and antibiotic levels. A significant interaction between antibiotic and protein levels was obtained for weight loss in sows at parturition and lactation, net gain in weight through the reproductive cycle, total and live pigs farrowed per litter.

Description: SummaryTwelve factorial experiments made from 1977 to 1981 compared the effects of 0, 4 and 8 t CaCO3/ha, 0 and 360 kg N/ha/year as urea and 0 and 60 kg P/ha/year as either superphosphate or ground rock phosphate on the yield and mineral composition of established grassland on soils of pH 4·7–5·6 in Northern Ireland.Lime did not increase yield whether urea was applied or not. It substantially reduced herbage Mn and, to a lesser extent, herbage P, Mg and Zn.With lime, ground rock phosphate was almost completely ineffective in raising yield and herbage P content. Without lime, it had some value but was less effective than superphosphate.Soil P extracted either by ammonium acetate at pH 4·2 or Olsen sodium bicarbonate reagent did not predict response to superphosphate. When the soil test values were adjusted for field bulk density, soil P extracted by ammonium acetate, but not by Olsen reagent, was significantly correlated with response.Herbage P in the first cut in 1978 was highly correlated with response to superphosphate; only sites with herbage P 〈 0·27% responded to P.

Description: The nutritional importance of a foodstuff in a diet depends on the composition of the raw foodstuff, the amount that is usually consumed and the extent to which nutrients are destroyed or lost during preparation of the diet.Most Nigerian foods have to be prepared and cooked before they can be eaten. A lot of food preparation in Nigeria involves soaking, steeping, boiling, frying and roasting; at each stage of the preparation, some of the nutrients may be discarded or destroyed, while in some cases toxic substances may be discarded (Oke, 1968)

Description: SummaryResistance to insects in cow peas was studied in a diallel cross and in a test cross. Number of pods and seed yield under unsprayed conditions, expressed as a percentage of their values under sprayed conditions, were confirmed as reliable characters for the assessment of resistance and as suitable for diallel analysis. Non-allelic interaction was not detected for these ratios despite its presence in yields. Resistance to flower damage by Maruca and resistance to all damage by post-flowering pests were both highly heritable and were controlled polygenically by alleles showing partial dominance.The test cross was not as informative as the diallel cross in the analysis of the genetic control of resistance in a group of moderately resistant lines, but was useful in selecting the best of these for future crosses. The results from both schemes suggested that resistance should be accumulated by intercrossing resistant lines before attempting to transfer it to agronomically-preferred susceptible lines.

Description: SummaryThe effects of including monensin in the diet on the dynamics of protozoa in the rumen of sheep were investigated using injections of protozoa labelled with 14C-choline.The half time of rumen fluid was higher in sheep receiving monensin but neither the pool size nor the composition of protozoa species (mainly smaller entodiniomorph ciliates) was significantly affected.More protozoa passed out of the rumen as liquid outflow rate increased and there was a tendency for the apparent production rate of protozoa to be higher with the resulting increase in washout of protozoa.

Description: SummaryA field trial of five contrasting types of white clover grown in monoculture was established in August 1978. Measurements commenced in October and continued for 12 months during which time no additional treatments were applied.Seasonal trends of dry-matter accumulation and distribution were recorded and particular reference was made to the components of harvestable yields, which showed a strong seasonal trend. During the summer the density of growing points decreased in all types except D while the number of leaves per growing point and mean dry weight per leaf increased. The principal component of yield, mean dry weight per leaf, increased later than number of leaves per growing point. Stolons did not show the same cyclical pattern and produced an overall increase during the experiment. The five genotypes also showed large variation in the distribution of dry matter between leaves, flowers, stolons and roots.

Description: SummaryInvestigations were carried out during 1976–80 on the alkaline alluvial soils of Daurala and Jullundur and on the acid hill soils of Simla and Shillong to study the effect of soaking non-dormant mother seed tubers in a solution of single superphosphate alone and in combination with urea, KCl, gum acacia and agromin (micro-nutrient mixture) on the tuber yield and P economy of the subsequent potato crop. On the alluvial soils, soaking increased the yield of daughter tubers but only on P-deficient soil. Increasing the period of soaking above 6 h and the concentration of superphosphate above 1·5% in the solution tended to reduce the emergence and tuber yield. On the acid hill soils soaking tubers for 4 h in a solution of 0·5% urea + 1·5% single superphosphate + 0·2% Dithane M-45 increased the yield of daughter tubers. Inclusion of KCl, agromin or gum acacia in the soaking solution had little effect. The increase in yield due to soaking was produced by an increase in number and size of daughter tubers and was equivalent to about 22 kg P/ha applied to soil.

Description: SummaryA production system is defined which involves the production of lambs from crossbred ewes kept in a cool, temperate grassland environment at an altitude of 250–300 m. Within the production system, an investigation was carried out on the effect of the timing of weaning, pre-mating treatment (flushing) and concentrate feeding before lambing in a flock of 180 Border Leicester (♂) × Scottish Blackface (♀) ewes maintained for a production span of four lamb crops. Weaning treatment had no significant effects on changes in live weight or body condition score. Pre-mating treatment affected live weight and condition at mating. It did not affect the number of lambs born but had a significant effect on the subsequent birth weight of twin lambs in the 1st year it was applied but not thereafter. The timing of introduction and total quantity of concentrate feed affected the birth weight of lambs from ewes at their first lambing (24 months old) but not subsequently. There were no long-term effects of treatment on ewe survival or on the production characters measured. The results are discussed in relation to the seasonal patterns of grass supply and the normal limits of commercial practice. In this study, when grass and forage were in reasonable supply, pre-mating management and concentrate feeding were not critical to ewe performance. Only in circumstances of an unusual grass shortage and also in young ewes did these factors have significant effects on performance.

Description: A number of factors affect predictions of rumen degradability of feedingstuffs when using the in sacco technique (Lindberg, 1983). One factor which exerts a great influence is the bag cloth aperture (Lindberg & Knutson, 1981; Lindberg & Varvikko, 1982). Without doubt part of the difference in degradation between pore sizes can be explained by differences in particulate matter losses (Lindberg & Knutsson, 1981; Lindberg & Varvikko, 1982). It has, however, also been suggested that the differences between pore sizes are due to the combined effect of differences in liquid exchange between the bags and the rumen contents and on the selection of microbes entering the bags (Lindberg & Varvikko, 1982).