An experiment was conducted during the rabi seasons of 1980–1 and 1981–2 to study the effect of exchangeable sodium percentage (ESP) of 87, 62, 44, 34 and 27 on growth, yield and chemical composition of toria (Brassica campestris var. Toria), raya (Brassica juncea L.) rapeseed (Brassica campestris var. Brown Sarson) and taramira (Eruca saliva). Number of branches per plant, number of siliquae per plant and seed yield of these crops were highest at 27 ESP. Increasing ESP decreased N, P, K, Ca, Mg, Fe, Zn, Cu and Mn concentrations and decreased that of Na in seed and stover. These crops can be grown successfully up to about 44 ESP without significant reduction in yield. Raya and rapeseed produced higher yields than the other oilseed crops on sodic soil.

Measurements were made at intervals during 1983–4 on the main stem and on tillers having defined morphological positions on plants of winter wheat cv. Avalon growing in a multifactorial experiment testing combinations of the following five factors: rotation, sowing date, amount of autumn N, amount of spring N, and timing of spring N. Some observations from similar experiments in the two previous seasons are also reported.

The tillers in the axils of the first three leaves (Tp, T2 and T3) appeared on most plants. An average of 1·8 other tillers were produced on each plant, including 0·14 at the coleoptile node. When number of shoots was maximal, main stems (M), T1 and T2 together accounted for 64% of the total number of shoots, 76% of the total green area and 87% of the total above-ground dry weight. More than half of the T1s died before maturity, two thirds of the T2s and almost all of the other tillers. The final population of 566 ears/m2 was made up as follows: M 56%, T1 26%, T2 16%. The differences between categories in dry weight per shoot at maturity were relatively less than earlier. Contributions to the mean grain yield of 9·9 t/ha were: M 60%, T1, 22%, T2 14%. M had more grains per ear than T1, or T2 which had similar numbers. Dry weight per grain was similar in all three categories.

Most of the effects of treatments on dry weight/m2, which have been described previously by Prew et al. (1986), were due to effects on all shoot categories. Several treatments increased the number of shoots/m2 by increasing the average number per plant of tiller categories that were produced later. This was always the result of an increase in the proportion of plants having many tillers. Neither the maximum number of tillers found on a plant, nor the duration of tiller production, was affected.

Both within and between tiller categories, shoots that were produced last died first. Plants which started tillering late produced fewer, smaller, tillers than average and relatively few of these survived. The standard hierarchical order of tiller production and survival was disrupted when plants were damaged by stem-boring insects and when the period shortly before a tiller category was due to emerge was unusually dull and warm.

The effect of exchangeable sodium percentages (ESP) of 86, 61, 43, 33 and 28 on forage yield and chemical composition of four cultivars of pearl-millet (LC-2, LC-5, LC-6 and LC-7) was studied under field conditions during 1981 and 1982. Dry and green forage yields were significantly higher at 28 ESP over other ESP values. Increasing ESP decreased the yield and concentration of Ca, K and P but increased that of Na in the plants. Cultivar LC-5 was found to give the best performance under sodic soil followed by LC-7, LC-6 and LC-2. At an early stage of crop growth (45 days), cv. LC-2 had significantly lower concentrations of Ca, K and P and a higher Na concentration compared with other cultivars.

The total glycoalkaloid (TGA) content of tubers of ten potato cultivars exposed to the light for 42 h significantly increased (P < 0·001). on average, above that of tubers kept in the dark. There were significant differences in the percentage changes in TGA content (P < 0·05) and in the intensity of tuber greening after exposure (P < 0·05) between cultivars although there was no correlation between the two characters.

Progeny of perennial ryegrass (PRG) plants selected for low and high leaf shear strength were sown in a spaced-plant field experiment and were shown to differ in leaf strength in the same direction, confirming this to be a heritable trait. Selection for low leaf shear strength also reduced weight per leaf length, but had no effect on dry-matter (D.M.) percentage, growth score, rust score or tendency towards aftermath heading.

Rates of D.M. consumption (g D.M./min) and ruminal degradation of D.M. using the polyester bag technique, were then determined with small quantities of the two PRG selection lines, and also white clover, using sheep fed a basal diet of fresh ryegrass/white clover pasture. Selecting PRG for low leaf shear strength slightly reduced concentrations of cellulose and hemicellulose, slightly increased total N concentration and increased rate of D.M. consumption by sheep (17%) but had no effect on rates of ruminal D.M. degradation. The selection thus moved the nutritional characteristics of PRG in the direction of white clover.

The first nutritional response to the selection appears to be a faster rate of D.M. consumption, and it is considered that leaf shear strength has potential for selecting PRG with increased rates of voluntary intake by ruminants.

The effect of P applications and native vesicular-arbuscular mycorrhiza (VAM) on the growth and P nutrition of red clover plants was studied in two acid hill soils with similar edaphic characteristics.

Mycorrhizal and non-mycorrhizal plants were compared under sterilized soil conditions. Plant growth increased on P addition in both soils, but the effect of mycorrhiza in improving drymatter production and P uptake was significant only in one of the soils. Fourteen and twenty-five mg/kg Olsen-P were needed in this soil to obtain the same yields by mycorrhizal and non-mycorrhizal plants, respectively. Results are explained in terms of a different effectiveness of the two fungal populations, and the possible effect of the soil sterilization process on percentage VAM infection is discussed.

With the current high prices for livestock, forage legumes are increasingly attractive to farmers in west Asia. There has been very little genetic improvement of the main species, of which three vetches, Vicia saliva (common vetch), V. villosa subsp. dasycarpa (woollypod vetch), and V. narbonensis (Narbon vetch), show promise. As a first step in genetic improvement 23 genotypes of common vetch and one each of woollypod vetch and Narbon vetch were grown at four sites in Syria and one in Lebanon over three seasons. Since local climatic conditions were considered to be of considerable importance, each site in each year was treated as a separate environment, to give 15 environments in all. genotype × environment (G × E) interactions were analysed using linear regression.

There was considerable variation in herbage and seed yields within both genotypes and environments, and G × E interactions were highly significant. In the case of herbage yield good environments could be defined as those receiving high rainfall and low incidence of frost. Several genotypes appeared to possess wide adaptation, in terms of both yield and stability. Climate, except for late spring rains, had little effect on seed yield, nor were any of the genotypes widely adapted. However, in the broad sense heritability was much higher for seed than for herbage yield.

There is a need to define good and bad environments for seed yield. Based on observations during the study it is likely that good environments for Narbon vetch are those where broomrape (Orobanche crenata) is absent, while root-knot nematode (Meloidogyne artiella) may affect seed yield of common vetch. In view of its high seed yield the possible role of Narbon vetch as a grain legume is briefly discussed.

Egg production and body mass changes were measured in six groups, each containing 10 single comb White Leghorn (SCWL) hens, in which each group received decreasing amounts of dry matter (D.M.) in decrements of 10%. Group 1 received 101·2 g D.M./day (100%), an amount normally offered these hens, whereas group 6 received 52·8 g D.M./day (50%). Egg production remained relatively high but body mass declined rapidly in the feed-restricted groups when compared with group 1 in the first 4 weeks (period I); in the second 4 weeks (period II), egg production declined to a great extent but body mass remained constant. Egg production and egg mass were significantly lower in period II than in period I in the feed-restricted birds. In period I egg production did not decrease significantly until the hens were restricted in feed by 30%; in period II this occurred at 20% feed restriction. Energy of eggs produced as a fraction of metabolizable energy intake (MEI) tended to increase in the feed-restricted groups when compared with group I in period I, but decreased significantly at the 40% and 50% group in period II. Maintenance energy requirements for the hens were 569·2 kJ/kg0·75 per day and the efficiency of utilization of energy for egg production was 88·2% in period I; these values were 551·6 kJ/kg0·75 per day and 74·0%, respectively, in period II. Energy yielded from the catabolism of body tissue per gram body mass loss was 23·08 kJ.

It was concluded that the hens initially maintained near-normal egg production at the expense of body energy reserves and then at the expense of egg mass. The efficiency of utilization of energy for egg production was higher when the energy source was mainly from body energy reserves than from MEI (88·2% v. 74·0%). The level of feed restriction and its length of imposition, the body energy reserves of the hen and the source of energy for egg production can explain many of the different responses reported in feed-restricted laying hens. In addition, reduction of 20 to 30 % feed intake in laying hens had little effect on egg production for a short period (4 weeks) during which time the hens mobilized body energy reserves. If these hens were to be sold, then this would add an additional option to this enterprise; that is, reduce feed cost at the expense of body mass prior to the sale of the hens.

Adaptive and productive traits were studied in three genotypes of cattle, Simmental (≥ 7/8 Simmental with residual Hereford) (S), Hereford (H) and F2et seq. Africander × Hereford (AH), selected from the 1985 and the 1986 branded steer groups (Years 1 and 2, respectively) fed low- and high-quality diets.

There were significant (P < 0·01) differences between years, breeds and diets for the two groups for live weights at the beginning and end of the feeding period, voluntary feed intake and fasting heat production. However, there was no breed × year interaction except in heat production per unit live weight because the AH had a higher heat production per kg than the H in Year 1 but lower in Year 2. Significantly lower values for feed intake (P < 0·01) and heat production (P <0·01) were recorded for S relative to AH and H when expressed on a live-weight basis; however, the ratio of intake to heat production was similar for all breeds.

The S breed had the heaviest birth weights and highest pre-weaning weight gains (P < 0·01) and the AH, despite having birth weights similar to that of the H, had higher pre-weaning live-weight gains (P < 0·01). There were significant (P < 0·01) breed differences for adaptive traits (except for the estimate of helminth resistance), with the AH being more tick- and heat-resistant and having sleeker coats than the other breeds.

There were no significant correlations between any adaptive trait and pre-weaning gain despite the fact that ticks, helminths and heat loads were evident.

This experiment shows that provided a low plane of nutrition is the only stress imposed on growing cattle, breeds such as the S will perform similarly to British breeds and may perform slightly better.

Two experiments were done in which the yield, digestibility and protein content of several autumnsown triticale cultivars were compared with rye and, on one occasion, ryegrass. Rye and an earlyflowering triticale cultivar (A208) had the highest early season yields and, at that stage, all cultivars and species had high digestibility.

When harvesting was delayed, the yield of later flowering cultivars (A386 or the latest flowering variety, A876) was greatest. When the plots were cut and harvested again, the intermediate and late maturing varieties (e.g. A386, A876–10) gave the highest yields of digestible dry matter. It was concluded that there was no advantage in using a mixture of cultivars as in the commercially available ‘Trical’ and that the available cultivars offered farmers useful alternatives in harvesting strategy and breeders the opportunity to develop earlier high-yielding triticale cultivars.

Three experiments are reported in which the photosynthetic rates of potatoes grown with various amounts of applied nitrogen (N) fertilizer were measured. Rates of photosynthesis in leaves of plants grown without applied N reached levels as high as those receiving N in all experiments. The rate of photosynthesis in the uppermost leaves of the variety Pentland Crown was found to increase during the season, whereas in Estima rates remained the same. Decline in the rate of photosynthesis with leaf age was more rapid in strongly shaded leaves than in less shaded leaves which were found to be photosynthetically active 8 weeks after expansion.

A number of mutant lines showing different levels of improved quantitative resistance to bacterial leaf blight (BLB) were obtained through selection of plants or lines derived from seeds of the rice cultivar Harebare exposed to thermal neutrons and gamma-rays. The selections were made on M2–M4 materials under natural BLB-epidemic conditions and/or by artificial inoculation of one of the BLB isolates. Bacterial isolates predominating under the natural conditions were identified as belonging to the differential BLB isolate group I, and the isolates of this group were used in the artificial inoculation for selection of mutants. The selected M4 mutant lines were tested in M5 for BLB resistance by artificial inoculations of four differential bacterium isolates, groups I, II, III and IV. The M6 mutant lines showed quantitatively elevated resistances to the isolate of bacterium group I and also to the other three differential isolates. Analysis of variance of the data demonstrated that the observed elevated quantitative resistances of the mutants to the isolates I, II, III and IV were isolatespecific. Host-parasite interactions in quantitative resistance to BLB and their modification by induced mutations are discussed.

The dates of transplanting and maturity of twenty-four experiments between 1980 and 1986 with the lettuce varieties Saladin and Saladin R 100 were used, together with meteorological data for each crop, to study the planning of crop continuity and the prediction of crop maturity. The interval in days from transplanting to maturity was shown to be a minimum for crops transplanted around the middle of June and was described by a fitted quadratic relationship which accounted for 34·6% of the variance. When expressed in accumulated day-degrees >0 °C the interval increased with later transplanting but a linear relationship accounted for only 22·2% of the variance. However, when expressed as accumulated solar radiation the interval decreased with later transplanting and a linear relationship accounted for 82·2% of the variance. When expressed in effective day-degrees (EDDs) the interval was relatively stable at 589 EDDs (S.D. = 39·5).

Predictions of commercial crop maturity based on these relationships and using a combination of average and observed meteorological data showed that EDDs gave the most accurate prediction. Differences between actual and predicted maturity appeared to be associated with the site of production, suggesting that a ‘site’ factor needs to be incorporated to take account of local differences in temperature, solar radiation and soil type. The use of long-term average day-degree and EDD data was less consistent than estimates of maturity based wholly or predominantly on observed day-degree and EDD data though with solar radiation the reverse was true.

Yields of the three ‘test’ crops, winter wheat, potatoes, spring barley in the Rothamsted Ley–Arable experiments 1949–69 increased by about 100%, 80%, 40% respectively, each in a period of 19 years. The wheat variety was changed once during the period and this change is enough to explain most of he increase of yield. For potatoes there was no change of variety; the estimated effects of changes in manuring, etc. explain less than one third of the observed increase. For barley two changes of variety explain about one third of the increase; most of the remainder may be explained by improved manuring of preceding crops, especially potatoes. After 1969 the cropping was drastically changed but a few recent yields from other experiments at Rothamsted indicate that the steady rates of increase may have continued at least up to 1980.

Rumen degradability of dry matter (D.M.) and N in wheat straw, rice straw and local grass hay, containing 5·16, 6·37 and 4·58 mg N/g D.M. respectively, was estimated by rumen fermentation measurements at 3, 6, 9, 12, 24 and 48 h using the nylon bag technique. The degradability of D.M. at an assumed rumen outflow rate of 0·025/h was 21·7, 34·9 and 22·4 for wheat straw, rice straw and grass hay, respectively. Theestimation of degradability of N was confounded by thedeposition of ruminal microbial nitrogen in the nylon bag. A correction was made by measuring the accumulation of N when N·free fibre and cellulose were incubated in the nylon bags. The effective degradability of N in the roughages at the assumed rumen outflow rate was 54·5, 36·9 and 42·8% respectively, showing that the roughages contain rumen-degradable N for microbial nutrition. The undegradable nitrogen (UDN) values in wheat straw, rice straw and grass hay were 2·35, 4·02 and 2·62 mg/g D.M., and after correction for unavailable acid detergent-linked N, the available UDN values were 0·58, 2·95 and 1·32 mg/g D.M., respectively.

A field experiment was carried out in three wet seasons of 1982, 1983 and 1984 with various combinations of urea and organic nitrogen sources to investigate the nitrogen transformation and productivity of rice crop in a waterlogged situation. The treatments used were: (i) control (No), (ii) FYM + urea, (iii) Sesbania + urea, (iv) urea, the levels of nitrogen being 60 and 90 kg/ha and the proportion being 50:50 between organic and chemical sources where such combination was used. The soil samples were analysed for ammonium, hydrolysable and non-hydrolysable forms of nitrogen at 15, 30 and 45 days after transplanting. The release of hydrolysable and non-hydrolysable nitrogen was superior in the urea-Sesbania combination while the release of NH4·N was slightly better in FYM-urea combination. Yield of rice and apparent nitrogen use efficiency were highest in sole urea treatment and almost similar in FYM-urea and Sesbania + urea combinations. A statistical nitrogen-transformation model outlined the relationship among the various forms of soil nitrogen under submergence. The model suggested a strong correlation among the different forms of nitrogen during the earlier period of submergence.

Carcass measurements including chemical composition and specific gravity data from 40 male and 40 female quails killed at 42 days of age were evaluated for use as an indirect means of estimating carcass fat. The results indicated that carcass fat was highly negative correlated to water (r = —0·93 and —0·87 for males and females, respectively) and that the inclusion of carcass protein improved the accuracy of prediction a little (r = -0·93 and -0·88). Carcass fat was only moderately related to specific gravity (r = —0·55 and —0·42) and the reliability as estimator of carcass fat was less than water or protein. Also, body weight was positively related to carcass fat (r = 0·71 and 0·42).

Field studies were conducted at Ilorin and Bacita during the 1985–6 cropping season to evaluate the use of hexazinone [3-cyclohexyl-6-(dimethylamino)-l methyl-1, 3, 5-triazine-2, 4(1 H, 3H)-dione] alone, and in combination with diuron [3,(3,4-dichlorophenyl)l-l dimethyl urea] in crops of sugar cane. Hexazinone, alone or in combination with diuron, effectively controlled a broad spectrum of weeds in a loamy sand soil at Ilorin. Most of the herbicide rates used were, however, severely phytotoxic to the crop. On silty clay-loam soils at Bacita, the same herbicide treatments, while giving effective control similar to that obtained at Ilorin, were not phytotoxic to the crop. Weed control effectiveness was influenced by the percentage of organic matter in the soils and by the amount of herbicides used. A broader spectrum of weeds was controlled by the mixture of hexazinone plus diuron than by hexazinone alone. There was no difference between the performance of the tank and formulated mixtures of hexazinone plus diuron.

In a 2-year study, the growth and yield of lowland rice increased significantly with the combined use of organic materials and N fertilizer in an acid-lateritic soil. Application of farmyard manure (FYM) or water hyacinth compost (WHC) at 10 t/ha along with paddy straw (PS) at 2·5 t/ha increased grain yield by 28%, similar to the increase given by 30 kg N/ha as fertilizer. The combination of FYM and WHC with or without PS produced yields equivalent to those using 50–60 kg/ha N as fertilizer urea. Uptake of N increased but the recovery of applied N decreased both with the application of organic materials and with increasing N. Organic materials considerably improved the fertility status of the soil, as measured by % C and available N, after crop harvest, whereas N fertilizer made no impact on fertility build-up.

Weaned lambs of mean weight 25 kg were offered a diet of mature oaten hay or hay supplemented with a pelleted mixture of oat grain and sunflower meal (2:1), at one of three rates, for 86 days. The effect of the supplement on the voluntary intake of hay was measured during the first 20 days when feed was offered twice daily (Expt 1), after which the effects on ruminal and post-ruminal digestion were investigated under continuous feeding conditions (Expt 2).

In Expt 1 the first increment of supplement increased the total intake of organic matter (OM) but increasing the supplement further, up to 510 g D.M., had no additional effect. The voluntary intake of oaten hay was not significantly reduced by the lowest rate of supplementation but at higher rates was depressed at a mean rate of 92 g/100 g supplement. Rates of change in fasted weight on the four treatments were —63, —5, 21 and 45 g/day, respectively.

In Expt 2, where the rates of hay intake were held at 85% of those achieved in Expt 1, the first increment of supplement increased the pool size of OM and cell wall components in the reticulorumen by about 50%. It also increased their outflow rates at the abomasum by 24% and 33%, respectively, but significantly decreased the fractional outflow rate and fractional digestion rate of cell wall components. Supplementation decreased the proportion of apparent OM digestion that occurred in the reticulo-rumen from 76% to 65%. The presence of supplement doubled the ammonia pool in the rumen and increased the abomasal flow on non-ammonia nitrogen (NAN) and microbial NAN by 70%. Estimates of the amounts of crude protein apparently digested in the intestines (DCPi) increased linearly with proportion of supplement in the diet. However, the apparent digestibility of the hay was decreased, rather than increased, by the supplement. Although higher rates of supplement did not significantly change the elevated rumen pools of OM and cell wall components, there was a consistent tendency for these to decrease.

The results are consistent with the view that the intake of unsupplemented hay was limited by its low nitrogen content and the intake of supplemented hay may have been limited primarily by the capacity of the reticulo-rumen, although other factors were increasingly involved at higher rates of supplementation.