ALBERT

Description: VIII. SUMMARYIn the introduction the crying need for research into animal nutrition under tropical conditions is emphasised. In Trinidad the stock are normally fed on mixed natural herbage grazed or cut from waste areas or from cultivated perennial grass crops. This system of rationing is a common one in many insular tropical climates.The experiment was designed to test the effect of stage of cutting on the yield and composition of Elephant Grass (Pennisetum purpureum), a perennial fodder grass widely cultivated in Trinidad to-day. Three times of cutting were chosen, namely series A—cut every four weeks, series B— cut every eight weeks, and series C— cut every twelve weeks.

Description: 1. In continuation of experiments made in 1949 (Holmes et al. 1950) an experiment was carried out from 7 May until 23 September 1950, to compare close-folding and rotational grazing of cows on pastures which were liberally treated with nitrogenous fertilizer. With close-folding the cows were moved daily to an area of fresh pasture calculated to supply the day's feed requirements; the rate of stocking for the day ranged from thirty to sixty-five cows per acre. With rotational grazing the cows were stocked on pasture at the rate of seven to eight cows per acre and moved from one pasture to the other at intervals of 3–4 days. Two uniform groups of six Ayrshire cows were used in a double reversal layout with four periods each of 5 weeks. The same pastures as in 1949—a permanent pasture and a cocksfoot ley—suitably divided by electric fences were used. No supplementary feeding was given.2. The average yield per acre from close-folding was 241 cow-days, 732 gal. of milk and 320 lb. live-weight gain—equivalent to 632 lb. digestible crude protein and 4316 lb. starch equivalent. Rotational grazing on similar adjoining paddocks gave 181 cow-days, 557 gal. of milk and 285 lb. liveweight gain per acre, equivalent to 486 lb. digestible crude protein and 3371 lb. starch equivalent.3. The average daily milk yield per cow was 29·5 lb. for one group and 30·2 lb. for the other. For close-folding it was 29·6 lb. and for rotational grazing it was 30·1 lb., none of the differences being significant. Nor were any differences in the average live weight of the groups or in their live-weight gains significant.4. The increased production per acre from closefolding compared with rotational grazing—amounting to 20–40%—could be related to the increased efficiency with which the available pasture was consumed.5. Close-folding had no harmful effect on the pastures. Although the season was exceptionally wet, poaching occurred only in the gates and alleyways. 6. The frequent applications of nitrogenous fertilizer throughout the season maintained regular production of good herbage. In June and July, however, despite the fertilizer applied, the crudeprotein content dropped on some paddocks to 13% of the dry matter, a figure barely sufficient to maintain high milk yields.7. Comparison of the production per acre in 1950 with that in 1949 where close-folding was used, showed an increase of 34% in starch equivalent utilized on the permanent pasture. For each extra cwt. ‘Nitro-Chalk’ applied in 1950 over that in 1949, 190 lb. starch equivalent were produced. On the cocksfoot the response to additional nitrogen was reduced because of potash deficiency induced by cropping for grass-drying in 1948.8. The factors affecting the increased production from close-folding and the fertilizer requirements of pasture are discussed.

Description: 1. Various portions of barley plants were made available for chemical tests from manurial experiments which were designed to test the effects of K treatment (broadcast and placed with the seed) on grain yield.2. The experiments were located at three centres differing in soil characters and K status. Centre A was severely deficient in K; centre B was moderately deficient and at centre C, K was adequate.3. A comparison was made between the results of the following tissue test methods for K, Mg, Ca, P and Mn: (a) diffusion method, using young leaf, mid-stem leaf, and internode respectively; (b) Waring blendor, and (c) ash analysis. Mn was not determined by the blendor method.4. The coefficients of variation for the quick tests compared favourably with those of ash analysis for K, Mg, Ca, P and Mn respectively. Variations in results in tissue tests for Ca were, however, significantly greater than those of ash analysis, at centre A (second sampling).5. Correlation coefficients between results of ash analysis and the tissue test methods for K, Mg, Ca, P and Mn were positive and significant for totals, treatment and treatment × sites, except for Mn in young leaf by diffusion method. The error term for P was also significant for the quick methods, thus decreasing the value of the correlations for this nutrient.6. Correlation coefficients of yields with ash analyses, Waring blendor and diffusion method (mid-stem leaf) analyses respectively were significant and positive for K and negative for Mg, Ca, P and Mn. This confirms an interaction of K with the other nutrients.7. Minimum K levels, determined 5 weeks after seeding, above which no further increase in yields may be expected at the three centres, were: by diffusion method, using young leaf, mid-stem leaf and internode, 700, 500 and 600 μg. extracted per. g fresh weight respectively; by Waring blendor using ‘tops’, 2000 μg. extracted per g. fresh weight; by ash analysis of tops 1·5% K in dry matter. There is evidence that these critical levels fall later in the season, especially in mid-stem leaves, presumably through translocation of K to the ears.8. Minimum levels of K required for optimum yields are above those associated with the onset of deficiency symptoms of the element. Thus chemical methods only can determine suboptimal levels of nutrients in relation to final yields.

Description: The last issue of this Journal (p. 132) contains a paper by Dr R. A. Fisher on the effect of Silica upon the growth of Barley at Rothamsted, which begins by stating that his data “show conclusively that the view previously rejected that the silicate acts by making available to the plant the actual reserves of soil phosphates must be regarded as strongly established.” Twice elsewhere Dr Fisher states that this erroneous conclusion of previous investigators is due to the fact that they had considered only the proportion of phosphoric acid in the ash and had overlooked the increase in the total phosphoric acid in the crop. As Mr Morison and I were the previous investigators in question I turned to our twenty-three-year-old paper with some curiosity to ascertain the grounds for this magisterial dismissal of our conclusions, for my remembrance of the subject did not tally with the opinion Dr Fisher attributes to us. Still less do I agree now that I have re-examined our original paper.

Description: The Papaya tree is common in all parts of India and is grown also in the Philippine Islands, Federated Malay States, Java, Ceylon, and other tropical countries.

Description: 1. Percentages of fat, solids not fat and protein were determined in over 700 samples of mixed milk from 15 herds during 1925–26. In the case of fat content, nine herds produced one or more samples below 3 per cent., one herd recording 25 per cent, of samples below this limit. With regard to solids not fat, twelve herds produced milk containing less than 8·5 per cent, on one or more occasions, the highest percentage of deficient samples recorded being 40.2. Frequency distributions of fat, solids not fat and protein percentages in the samples analysed, are given, together with standard deviations, and mean percentages with probable errors for these three constituents.3. Correlation tables of fat with solids not fat, and protein with solids not fat have been prepared, and graphs illustrating the variations are given.

Description: The investigation which has been dealt with in this communication was essentially a continuation of earlier work carried out in 1925 and was primarily designed with the object of ascertaining whether, under greatly differing conditions in respect of soil, herbage and weather, the striking results obtained in the 1925 investigation concerning the chemical composition, digestibility and nutritive value of pasture herbage, under a system of cutting resembling the conditions of close grazing, still held good.

Description: It has been shown that in this trial the increase in milk yield of the nine cows considered as a herd is within the limits normally expected in the case of thrice-daily milking.The increase in the case of the heifers is below expectation, and the probable reasons for this are indicated.The effect of three 8-hour intervals on butter-fat percentage has been studied, and it is shown that as far as the individual cows are concerned there is little difference between the number of low fats produced under thrice milking at equal intervals and twice milking at unequal intervals in the case of the herds specified. It is shown that the reason for the bulk milk of the thrice-milked cattle maintaining a high standard of fat percentage at each milking is that each individual cow maintains a fairly high level consistently at one specific milking, and that this is not the same milking for each cow.

Description: The object of this series of investigations is to secure detailed information concerning the composition, digestibility and nutritive value of pasture grass in its different stages of growth. The results which were obtained in these respects by cutting the herbage of the experimental pasture plot at weekly and at fortnightly intervals have been described in previous communications. During the season of the present experiment, the trials have been carried a stage further by the adoption of a system of cutting at 3-weekly intervals. The main findings of the 1928 investigation are recorded below:(1) Chemical composition of 3-weekly pasture cuts: The adoption of a more lenient system of cutting at 3-weekly intervals led to a slight lowering of the percentage of crude protein in the grass and a slight raising of the percentages of crude fibre and N-free extractives. On the other hand, no corresponding effect was noted in respect of the ether extract, SiO2-free ash, lime and phosphate, the percentages of these constituents being very similar in the weekly and 3-weekly pasture samples obtained in 1928. The falling off of the percentage of crude protein in the 1928 3-weekly-mown herbage, as compared with the weekly and fortnightly-mown herbage of 1925 and 1927 respectively, was not wholly the consequence of the more lenient system of cutting, but was also due in part to the protein-depressing influence of the droughty periods which were experienced in the 1928 season.