In a field experiment where winter wheat and winter barley were sown on the same date, the patterns of root growth of the two species were similar, with a few roots reaching a depth of at least 120 cm. Roots senesced sooner in barley, in association with earlier maturity of the shoots and grain. The number of shoots and leaf area index of the barley were greater than for the wheat, but rates of dry-matter production until anthesis of the barley were similar in both species. The grain yield of wheat was about 10% heavier than for barley. Where chlormequat had been applied in early December at the 3- to 4-leaf stage, when shoot apices of both species were still vegetative, root density of the winter wheat in the following March and April was slightly greater than for untreated plants, but the difference disappeared later. For winter barley there was no effect of chlormequat on root growth until July when root length tended to be greater at depth after the chlormequat treatment. The chlormequat treatment significantly shortened stem length, but did not significantly affect the number of shoots, crop dry weight or grain yield of either species.

The amounts and rates of release of the different categories of soil K were measured on 21 soils from field experiments in England, Wales and West Germany using a calcium saturated cation exchange resin. The soils contained various amounts of exchangeable, fixed and matrix K; some contained no fixed K at all. These amounts could be qualitatively related to the clay contents of the soils.

Regression analyses of K removed at harvest by spring barley, winter wheat, field beans and sugar beet, grown in the field experiments, were made on the quantities measured by the Ca-resin method and on K exchangeable to M ammonium acetate (EK). The Ca-resin method proved a better predictor of K availability than EK for all four crops. A multiple regression of the amount and rate of release of exchangeable K, and the rate of release of fixed K, as measured by Ca-resin, gave the best correlation with K removed. The contribution of fixed K to the regression increased with the demand of the crop for K and with the length of time the crops had been grown without K fertilizer. For the cereals, fixed K appeared to be either completely available or unavailable depending on whether its rate of release exceeded a critical value characteristic of each crop.

The Ca-resin method is probably the best method available for measuring K reserves. It is, perhaps, too laborious for routine soil analysis, but could be used to characterize the long-term K release properties of a soil.

A 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.

In 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.

Four 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.

A series of experiments in Tasmania examined the growth, development, yield and components of yield of new Australian oil-seed rape cultivars from Victoria and Western Australia. The highest yields obtained were around 5·5 t seed/ha, from an autumn sowing with supplementary irrigation. Spring sowings with irrigation or autumn sowings without produced up to 4 t/ha. The Victorian lines with Japanese parentage clearly outyielded the Western Australian cultivars or Midas, a widely grown Canadian cultivar. When autumn sown, the Victorian lines grew more rapidly at low temperature, which under conditions of later stress contributed to a high yield relative to the other cultivars. However, the most consistent feature from both autumn and spring sowing was high rates of seed survival, up to near the potential number of around 30 per pod, giving very large numbers of seeds per m2. While individual seeds in the Victorian lines, particularly Marnoo, were smaller than in Midas, oil content remained high except under extreme stress in the later stages of seed development.

Propionate and glucose metabolism were compared in two groups of Scottish Blackface ewes, one in which ewes had been fitted with vaginal pessaries impregnated with progesterone-analogue for the synchronization of oestrus and the other when ewes were in anoestrus. In ewes given the same amount of feed, the production rate of propionate increased significantly (P < 0·05) from 33 in anoestrous ewes to 44 gC/day in ewes with pessaries. The proportion of glucose-carbon apparently synthesized from propionate also increased significantly (P < 0·05) from 0·31 in anoestrous ewes to 0·44 in ewes with pessaries. The proportion of glucose-carbon apparently recycled was also significantly (P < 0·01) increased from 0·12 to 0·22. No changes were observed in glucose concentration, production rate or oxidation rate between the two groups of ewes.

Ninety-two British Friesians (56 cows and 36 heifers) were divided into two groups during weeks 3–10 of lactation and received ad libitum either complete diet H (65% concentrates, 35% grass silage, 11·7 MJ ME/kg D.M.) or diet M (50% concentrates, 50% grass silage, 11·2 MJ ME/kg D.M.). In weeks 11· 20 half the animals of each group continued to receive the same diet (HH or MM) while the other half were changed from diet H to M (HM) or from diet M to L (ML). Diet L contained 35% concentrates, 65% grass silage and 10·7 MJ ME/kg D.M. The crude protein concentration of all diets was maintained at about 157 g/kg D.M. by the addition of soya-bean meal to diets M and L.

During weeks 3–10 the mean D.M. intake (kg/day), milk yield (kg/day), milk protein (g/kg) and live-weight change (kg/day) for animals on diets H and M were 15·0, 21·7, 33·3, 0·50 and 12·9, 20·2, 31·5, 0·35 respectively. Differences were significant for D.M. intake, milk yield and milk protein concentration. Although milk-fat concentration of cows given diet H (40·2 g/kg) was similar to that of cows given diet M (39·9 g/kg), heifers receiving diet H had a significantly lower value (37·0 g/kg) than those given diet M (39·8 g/kg).

When animals were changed from diet H to M or from M to L at week 11, D.M. intake, milk yield and milk-protein concentration decreased. However, milk-fat concentration and live-weight change were generally unaffected.

During the complete experimental period, weeks 3–20, animals on treatments HH, HM, MM and ML had mean D.M. intakes and milk yields of 15·3, 14·2, 13·2, 12·4 kg/day and 19·7, 18·5, 17·8, 17·0 kg/day. Milk-protein concentration, was closely related to D.M. intake, but only with heifers did diet H significantly depress milk-fat concentration. The highest live-weight gain was recorded on treatment HH (0·40 kg/day) and the lowost on treatment ML (0·29 kg/day) with intermediate values for treatments HM and MM.

In vivodigestibility coefficients of D.M. and organic matter for diet H (0·731, 0·757) were significantly higher than those of diet L (0·707, 0·734) with intermediate values for diet M. However, for acid-detergent fibre the digestibility coefficient for diet H was significantly lower (0·562) than for diet L (0·662). The digestibility coefficients for nitrogen in all three diets were similar.

Estimates of mean efficiency of utilization of ME for lactation were made on a weekly basis and were 0·56 and 0·64 for animals on diets H and M in weeks 3·10. During weeks 11·20 the mean values for animals on treatments HH, HM, MM and ML were 0·46, 0·53, 0·51 and 0·59, respectively.

Experiments 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.

The 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.

Vascular 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.

The air over a crop of flowering winter oil-seed rape was sampled for 39 days with an automatic volumetric spore trap. Considerable quantities of rape pollen were caught on most days. Density of pollen showed marked diel periodicity; few grains were caught at night and at mid-day, peaks occurred in late morning and early afternoon. It is concluded that wind plays a considerable role in pollination of the crop.

The 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.

A Scanning Electron Microscope was used to measure wool fibre diameter, the number of cuticular scale edges, crimp wavelength, the number of shed fibres, and the number of fibre loops in normal and cotted fleeces. The main difference observed was the greater number of loops in the cotted wools. There was no evidence of an increased number of shed fibres in the cotted fleeces.

Field 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.

Topsoils from eight different soil series were substituted for the local soil in three arrangements involving two depths of topsoil and either local or sand subsoils. A rotation of crops was grown with uniform annual N, P and K treatments for 24 years. A peaty soil produced the highest yields of grain, straw and grass, presumably because it released more N than the mineral soils, but an average yield of swedes. No mineral soil consistently produced higher yields of all crops and, although there were some significant differences, the variations in yield were generally relatively small. The deep topsoil consistently produced the highest yields. Topsoil with sand subsoil gave the lowest yields of grain, straw and swedes but not of grass.

All the crops on the peaty soil had higher concentrations of P in the dry matter than those from the seven mineral soils. Crops and herbage on the Laurencekirk and Foud-land soils had consistently slightly higher P concentrations than those on the other five mineral soils. Compared with the amounts applied, the crops removed considerably more K but only 45–68% of the P. There were large differences in the proportion of the P residues extractable by acetic acid from the different soil series.

The depth of topsoil was at least as important as soil type in determining yield, and the results support the use of soil depth as one of the main factors used in the Land Capability Classification for Agriculture.

A 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 <0·01) using the colour measurements. In a further examination comparing 23 cultivars, 68% of all possible cultivar pairs were separated (P <0·01).

Effects 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.

Commercial 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.

Conformation of carcasses from 107 Romney ewe lambs was determined using two visual scoring systems and the scores related to chemical and dissected carcass composition. The conformation system which evaluated the lateral profile of the hind leg failed to improve the prediction of carcass composition. The Meat and Livestock Commission system used in Great Britain separated carcasses on weight and fatness, the higher classes having the heaviest and fattest carcasses. After adjustment for carcass weight and fatness the higher conformation classes had the lightest bones and the heaviest weight of muscle, and some of the muscles weighed were shorter and deeper than those of the lower conformation classes.