ALBERT

Description: Grundy & Healy (1950) developed a method of ‘restricted randomization’ applicable to factorial experiments of 2n or 3n type laid out either in quasi-Latin squares of size 8 × 8 or 9 × 9, or in blocks of 8 or 9 plots. This method of randomization, while in no way affecting the validity of the normal analysis, prevents the appearance of designs with obviously undesirable features. Grundy & Healy gave an example of a quasi-Latin square inwhich the main effect of one factor corresponded to the pattern:

Description: SummaryThree short-term experiments on green-manuring are described. In the first, trefoil (T) and ryegrass given fertilizer N (RN) increased the yield of a following barley crop grown without fertilizer N by 500–900 kg/ha, but did not affect yield of barley given N. In the second, T and RN increased yield by 1400 kg/ha whether or not fertilizer N was given to the barley. Ryegrass without fertilizer N (R) had smaller effects in both experiments. The third experiment (with different treatments) suggested that the effect of trefoil was caused by the greenstuff turned in, not by any physical or microbiological change in the soil.

Description: SUMMARYExperiments with spring barley in 1975–7 tested fungicides applied to control powdery mildew (tridemorph) or brown rust (benodanil) in factorial combination with six amounts of fertilizer N, applied either to the seed bed soon after sowing, as a later top dressing or half at each time.Powdery mildew was the principal leaf disease in all three years. It tended to be increased by increments of N and by applying the N late but much less consistently in the first two years, when soils were very dry for much of the growing period, than in 1977 when amounts of rain were much closer to the long-term mean. Tridemorph significantly increased the number of ears in 1975, mean number of grains per ear in 1976 and 1000-grain weight in all three years; it gave net increases in grain yield of 0·55, 0·68 and 0·41 t/ha, respectively, in 1975–7. Yield response to increasing amounts of applied N was greatly increased where mildew had been controlled by the use of tridemorph, and was better where the N had been divided into two dressings than where it had been applied as a single dose. In 1975 and 1977 the biggest responses to tridemorph were obtained with late N but in 1976 yield was increased most by tridemorph where the N had been applied to the seed bed.Analyses of samples taken in 1977 showed no significant effect of tridemorph sprays on concentrations of either N, P or K in the green crop. By contrast, analyses of grain samples in 1976 and 1977 showed that amounts of N in grain (mg N/grain) were affected by amounts of applied N and by tridemorph, and that there were interactions between these two factors. Concentrations of N in the grain (% D.M.) were also determined by the effects which these factors had on grain size. At small N rates tridemorph mostly increased grain size so that N concentrations were decreased by the fungicide. At large N rates increases in grain size where tridemorph had been applied were accompanied by increases in the N content of the grain (mg N/grain) so that N concentrations were either unaffected (1976) or were increased (1977) by the fungicide. With 90 kg/ha of applied N the fungicide increased the amount of N/ha removed in grain by over 21 % in each year. The apparent recoveries of N in these plots were increased from 66 to 81 % and from 87 to 105%, respectively, in the two years. Tridemorph had no significant effect on concentrations of P or K in the harvested grain but increased average amounts of these nutrients removed in the grain by 17 and 14%, respectively, in 1976 and by 14 and 7% respectively, in 1977.Examination of black and white, infra-red aerial photographs of the experiments showed that, in each year, the brightness of individual plot images was significantly correlated with grain yield.Complex designs without division into blocks are especially vulnerable to positional variation. Alternative methods of adjusting for such positional variation were compared in analyses of grain yields. The potential improvements in precision which might be achieved by the appropriate use of such analyses, and the difficulties of ensuring that unacceptable subjectivity and bias are not thereby introduced into the analyses, are discussed.

Description: SUMMARYSimple series of trigonometric terms (Fourier series) give good representations of response curves including sigmoid curves and intersecting straight lines.

Description: SummaryFive experiments in harvest years 1980–2 tested the effects of straw inoculum and fungicides on leaf blotch (Rhynchosporium secalis), growth and yield of winter barley. Inoculating plots with rhynchosporium-infected straw increased the rate of disease development and greatly decreased seedling growth but inoculating plots with wheat straw or sterilized barley straw had no effect. In 1982, plots inoculated with infected straw gave less grain than uninoculated plots, but in all years fungicide sprays applied in winter or early spring had mostly small effects on grain yield that were only poorly related to their effects on leaf blotch and seedling growth.

Description: SummaryExperiments of balanced design in harvest years 1981 and 1982 were used to measure interactions between plots of winter barley with different amounts of leaf blotch, caused by the splash-dispersed pathogen Rhynchosporium secalis. On the appropriate transform scales (logarithms of counts and logits of percentages), the effects of extreme treatments on neighbouring plots were up to 30% of the effects of the same treatments on the plots to which they were applied. Powdery mildew (Erysiphe graminis f.sp. hordei) was commonly least severe in plots with most leaf blotch except soon after fungicide sprays had been applied which, although chosen to decrease leaf blotch, also had short-lived effects on mildew. Consequently, contrasts in mildew between differently treated plots changed sign during the season. The effects of the same treatments on neighbouring plots similarly changed with time but not necessarily in phase with their direct effects. Analyses of the rhynchosporium data that recognized the effects of neighbouring treatments typically had much smaller residual mean squares than analyses that ignored neighbour effects but assumed randomized block designs.Treatments had mostly small effects on grain yield but these data from two of the experiments showed marked positional variation. Individual plots yields from one of these experiments, testing five treatments, are quoted in the appendix so that they are available to others with an interest in alternative methods, such as nearest-neighbour models, to adjust for local correlations between plots.

Description: SUMMARYTwo experiments compared yields of spring barley following barley, oats, beans (Vicia faba), red clover (cut) and (one experiment only) oil-seed rape, and tested effects of trefoil (Medicago lupulina) undersown in the preliminary crops of barley and oats. N fertilizer was applied at two rates to preliminary crops, and four rates to the final crop in each experiment. Barley following barley suffered severely from take-all disease (Gaeumannomyces graminis var. tritici); barley after other crops was little affected. Other recognized soil-borne diseases were unimportant. Barley yielded less after barley than after other crops except where excessive N fertilizer caused lodging. Clover and beans left N residues equivalent to about 88 and 44 kg fertilizer N/ha respectively; undersown trefoil left inconsistent N residues. Couchgrass (Agropyron repens) was more prevalent after barley than after other crops.