A field experiment using 15N was carried out at the Indian Agricultural Research Institute, New Delhi during the crop year 1985–1986 to investigate the possible economy in fertilizer nitrogen applied to rice and succeeding wheat by growing a summer leguminous green manure (Sesbania aculeata) and incorporating it in soil before transplanting rice. Grain and straw yields of rice with 60 kg N/ha after green manuring were slightly greater than with 120 kg N/ha after summer fallow. Thus summer green manuring can lead to an economy of 60 kg N/ha in rice. 15N analysis showed that green manuring contributed 4·7–5·6% N of the total taken up by rice and 1·9–4·8% of that taken up by the succeeding wheat, depending upon the rate of fertilizer N applied to rice.

15N analysis showed that at 60 kg N/ha applied to rice, 35·4% was recovered by rice, 41% by the succeeding wheat and 16·7% was left in the 0–45 cm soil layer after summer fallow; after green manuring 32·8% N was recovered by rice, 3·0% by succeeding wheat and 22·6% was left in the soil. Thus 56·2 and 58·4% of applied N could be accounted for after summer fallow and green manuring, respectively. At 120 kg N/ha about 60–61% of applied N could be accounted for. Thus about 40–44% of N applied to rice was lost by the various loss mechanisms operating in rice fields.

This paper describes an investigation into yield variability and spatial correlations in 129 spring barley trials using small plots between 2·4 and 6·0 m2 in area. We report on the efficiencies of the generalized lattice designs used, and discuss the effects of plot size and year-to-year variations. Results indicate that the recommendations of Patterson & Hunter (1983) on choice of block size apply equally well to small-plot trials. The observed variability and correlations are then discussed and so is the potential for improvement by using alternative designs. Patterns of variability were not at all consistent from year to year, or even between trials in the same year, but it appears important to take account of column effects as well as row effects.

Experiments were conducted in 1986 and 1987 to determine the influences of plant raising temperature, transplant age, N top-dressing and irrigation regime on the curd initiation and maturity characteristics of the cauliflower variety White Fox. The prime objective of this work was to determine whether changes in crop production practice had an influence on the period between curd initiation and maturity, in order to aid the development of techniques predicting when curds will reach a specific size.

The duration of the period from curd initiation to curd maturity was not significantly affected by any treatment in either year and treatment effects on curd size at maturity were of no practical importance provided that the recommended level of N top-dressing was achieved. It is therefore concluded that changes in production practices within the normal commercial range are unlikely to have any significant practical effect on the use of techniques to predict the timing of crop maturity.

There were large differences between the experiments in the mean number of leaves formed at curd initiation, which ranged from 22·0 to 36·7. In order to interpret these data a relative vernalization stimulus was calculated from 12 leaves onwards. It had a maximum rate of vernalization between 5 and 17 °C and a reduced rate at lower and higher temperatures and adequately accounted for the differences in the number of leaves at curd initiation.

Seventeen tree species (16 legumes and Eucalyptus saligna) were grown for 4 years on an Ultisol of pH 4·5 at Nakau, South Sumatra, Indonesia. Leaf and wood yields were recorded seven times during the 4-year period and mineral and plant quality measurements were made on leaf samples from the first harvest taken 2 years after transplanting. At this time, leaf and wood yields were highest from Acacia mangium but the yield of this species declined over time. Highest leaf production was recorded for Cassia siamea over the 4-year period.

Mineral analyses of leaf indicated N, K, Ca and Mg to be adequate for animal production in all species. P was below the critical level for animals in all species and Na levels were adequate only in Acacia mangium and Acacia auriculiformis.

Plant quality measures (ADF, NDF, lignin) suggest marked differences could be expected in potential feed value between species through differences in voluntary intake and digestibility.

The use of stock management has been shown to be an effective means of manipulating numbers of the grey field slug, Deroceras reticulatum (Muller). At stocking rates of 1500 sheep days/ha or more, slug control in excess of 90% can be achieved with the flexibility of employing various combinations of stock numbers and length of grazing period. In the same trials methiocarb slug baits applied at 10kg product/ha gave 50% control of slugs. A quantitative sampling technique was developed and is briefly described.

Pre-emergence herbicides applied at field recommended doses, 3 days after transplanting (DAT) rice plants, inhibited growth and N2-fixation of Azolla pinnata (Bangkok) and BGA (blue-green algae) inoculated 10 DAT. This inhibition was up to 15 DAT in Azolla and up to 20 DAT in BGA. Butachlor and Oxadiazon resulted in higher toxicity to Azolla and BGA than Benthiocarb and Pendimethalin. The application of 0·5 kg/ha active ingredient of 2,4-DNa did not inhibit growth of Azolla but inhibited BGA growth. However, 2,4-DEE, a post-emergence herbicide, applied 30 DAT showed inhibitory effects on the growth and N2-fixation of both Azolla and BGA. Inoculation of 2·0 t/ha of fresh Azolla 10 DAT produced maximum biomass within 20–25 days of herbicide treatments, depending upon the season. The inoculation of 10 kg/ha of a dry mixture of BGA 10 DAT could produce the maximum biomass 60 and 80 DAT in control and herbicide treated plots, respectively. The biomass and nitrogen produced by Azolla recorded at maximum mat formation were similar in both herbicide treated and untreated plots, but in BGA these were higher in controls than those of herbicide treated plots.

The use of Azolla and BGA biofertilizers along with herbicides increased the grain and straw yields, and panicle number and nitrogen uptake, by rice over no Azolla or BGA treatments. The Azolla and BGA treatments even without weeding increased rice yield up to that of herbicide and biofertilizer treatments.

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.

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.

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.

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.

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.

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.

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.

A study was conducted at Debre Zeit, Ethiopia to examine the differences in mineral composition, root N contents and their rates of transformation in the soil of different species of four genera of forage legumes, Trifolium steudneri (ILCA D/Z), Trifolium steudneri (Shola), Vicia dasycarpa (ILCA 6795), Vicia benghalensis, Lablab purpureus cv. Rongai, Lablab purpureus cv. Highworth, Medicago scutellata cv. Snail and Medicago truncatula cv. Barrel. M. truncatula cv. Barrel had higher N and P values than M. scutellata in both roots and tops. Root N contents of the legumes ranged from 2·43% for Vicia to 0·87% for Lablab. These differences were also reflected in the rates of organic root N transformation in soil as determined in laboratory incubation studies.

The P concentration in the tops of the legumes ranged from 0·32% in Vicia to 0·14% in Medicago spp. The observed P concentration in the Medicago species suggests a low internal P requirement. Potassium concentrations in the Trifolium species were much higher than the average for all legumes.

The results suggest that the Vicia species used in this study could contribute a considerable amount of N to subsequent crops even when the tops are not returned to the soil. Also, the Medicago species are more likely to thrive better under low soil P conditions than the other legumes.

Blood samples were collected three times weekly for 21 days before and after calving (day 0) from 29 buffalo cows and 22 buffalo heifers. Plasma concentrations of progesterone and total oestrogens were quantified by validated radioimmunoassays. Ovarian activity and uterine involution were monitored by rectal palpation at the sampling times and extended up to 60 days postpartum. The concentration of plasma progesterone in cows declined from 3·0 ± 0·2 ng/ml (mean ± S.E.) during days 21–17 before calving to 2·1 ± 0·1 ng/ml at day −3, followed by a rapid fall during the last 3 days of gestation, reaching 1·2 ± 0·3 ng/ml at the day of parturition. In heifers, plasma progesterone values increased slightly from 2·9 ± 0·2 ng/ml at days 21–19 before parturition to 3·4 ± 0·3 ng/ml by day −1 and then fell sharply to 2·1 ± 0·1 ng/ml at calving time. During the postpartum period, plasma progesterone decreased gradually and reached baseline values after day 15 postpartum, when the residual corpus luteum of pregnancy had completely regressed in all the animals studied. The plasma concentrations of total oestrogens started to increase at day −15 in cows and day −5 in heifers from below 40 pg/ml to 122·5 ± 51 pg/ml for cows and 100·7 ± 3·4 pg/ml for heifers by day −1. This was followed by a sharp increase to 251·2 ± 17·3 and 240·5 ± 10·1 pg/ml in these animals at the day of calving. Immediately after parturition, total oestrogens dropped abruptly to the lowest values and remained below 30 pg/ml in all cows and heifers until the end of the sampling period. We concluded that female foetuses significantly (P < 0·05) increased the maternal total oestrogens. Moreover, animals having postpartum disorders had significantly higher values for progesterone (P < 0·05) and lower values for total oestrogens (P < 0·01) than those having normal puerperal periods, but the magnitude of this difference varied in samplings between cows and heifers.

Pulse crops play an important role in Indian agriculture because of their unique ability to fix atmospheric nitrogen. Greengram, blackgram and soya bean are commonly grown during the kharif season (July–October) in Northern India. The availability of pulses is decreasing due to a decrease in area. Average yield of these crops is rather low and subject to great variation due to the vagaries of weather and pest attack.

Copper has been identified as a deficient micronutrient in many alkaline calcareous soils of Pakistan (Kausar et al. 1979; Anon. 1986b). Copper extracted with DTPA from several soils of Pakistan correlated significantly with organic matter and free CaCO3 content (Kausar et al. 1979). Both soil organic matter and CaCO3 content have been reported by Viets (1962) to be among several other factors that affect Cu solubility and hence the Cu nutrition of plants. Working with temperate acid soils, several investigators (McLaren & Crawford, 1973; Shuman, 1979) have recently used different extractants and indicator plants to characterize the chemical pools which appear to control plant available Cu. Shuman (1979) separated various soil fractions and determined their Zn, Cu and Mn content. However, the distribution of Cu among various fractions in alkaline calcareous soils of arid regions has received little attention. The object of the present study was to investigate the relationship between the Cu content of wheat, and native soil Cu and applied Cu. The contribution of Cu in various soil fractions towards plant uptake and that extracted by different reagents was also ascertained.