A simulation study was conducted to determine the relative response to selection of a one-dimensional spatial analysis of field experiments (SAFE) specifically adapted for early generation trials. The primary purpose of the analysis in these trials is to obtain accurate estimates of genotypic effects of the unreplicated test lines by adjusting for local variation, using either the yields of all neighbouring plots or the yields of neighbouring plots of (replicated) check varieties. The response to selection of the SAFE analysis, relative to the use of unadjusted yields of test line plots, was consistently greater than the relative response to selection of check-plot-only analyses. The relative response to selection of SAFE increased as the percentage of trend variance increased.

Winter barley cv. Igri, winter wheat cv. Avalon and spring wild oats (Avena fatua) were studied in monocultures in pots and in the field. The field experiments were located near Bristol and Bury St Edmunds in 1988/89. Pot sowings were monthly, whereas there was a single sowing date for each of the two field locations. Base temperatures for emergence in pots were 2·2, 1·3 and 2·3 °C for barley, wheat and A. fatua respectively. Barley was consistently the fastest to emerge. Leaf number was strongly correlated with photothermal time from emergence, with barley producing leaves at the greatest rate. Base temperatures for leaf appearance were −6, −5 and −3 °C for barley, wheat and A. fatua respectively. The field studies confirmed the ranking of the species based on the pot experiments. Both a model based on photothermal time and one based on rate of change of daylength at emergence gave good descriptions of the data. It is argued that correlations of rates of development with individual environmental variables are not sufficient to deduce the underlying mechanisms.

A trial using a split-plot with blocks design was carried out at the INTA Balcarce Experimental Station, Argentina on a typic argiudol soil to evaluate N nutrition in wheat after different preceding crops and using two rates of N fertilization (0 and 90 kg N/ha).

Wheat (Triticum aestivum), soyabean (Glycine max), sunflower (Helianthus annuus) and maize (Zea mays) were grown in different combinations for two successive years (1984/85 and 1985/86).

No water stress was detected during either growing season. Nitrogen availability was altered by the previous crops grown, but the effect lasted only for one season. Wheat following maize yielded least with no N and responded most to N fertilization. The highest yields of wheat without N and the lowest response by wheat to N fertilization were found after crops of soyabean and sunflower.

Wheat after a fertilized wheat crop did not respond to N fertilization because of a serious attack of take-all (Gaeumannomyces graminis tritici).

The nitrate concentration in wheat stem bases was found to be a good estimator of the availability of soil N.

Leaf proportions (LP) were determined in spring barley straws harvested at Cambridge in 1984 and 1985. Linear regression equations showed that a greater number of days to flowering increased LP whilst greater plant height decreased LP in spring barley straws. Plant height accounted for more than 70% of the variance in LP. By contrast, grain yield and stem diameter accounted for only a small percentage of the variance in LP. Straws from two-rowed winter barleys had slightly higher LP than six-rowed winter barleys but LP in winter and spring barleys were similar.

Leaf blade and leaf sheath fractions of the straws had lower acid detergent fibre and lignin contents and were more digestible than the stem fractions. Linear regression equations of straw digestibility in spring barleys on LP, grain yields, days to flowering and plant heights showed that LP accounted for a higher percentage of the variance in digestibility in 1984 than the other characteristics. In 1985, when harvesting conditions were unusually wet, grain yield accounted for the highest percentage of the variance in straw digestibility.

There were no differences in chemical composition and straw digestibility between two-rowed and six-rowed barleys, but winter barleys had higher straw digestibility than spring barleys. Date of sowing did not influence straw quality in two-rowed winter barleys.

The ranking of two-rowed spring barleys for LP, chemical composition and digestibility suggested that varieties with consistently better straw quality could be identified.

Residual nitrogen from white clover/ryegrass swards and ryegrass monocultures was quantified in terms of the barley yield obtained after ploughing the swards. Clover/ryegrass swards based on small and medium-leaved cultivars of white clover and ryegrass monocultures were grazed continuously by sheep for 3 years (1984–87) at the Welsh Plant Breeding Station, Aberystwyth, ploughed in the following spring (1988) and then sown with the spring barley cultivar Doublet. Yield of barley obtained after clover/ryegrass mixtures was 50% greater than barley harvested after ryegrass monocultures. Barley yield was 1·6 t/ha more following the white clover cultivars Gwenda and SI84 with ryegrass than following ryegrass monocultures.

In an intermediate deepwater situation (15–50 cm) at Cuttack, India, three improved high-yielding rice varieties, Utkalprabha (semi-tall), CR 292–8051 (intermediate tall) and Gayatri (semi-dwarf) were sown on 20 May, 30 May and 10 June in 1988 and 1989 with an application of either 0, 20 or 40 kg N/ha at sowing. Tall varieties performed better than the dwarf type but grain yield decreased with delay in sowing. The early-sown crops (20–30 May) germinated with pre-monsoon rains and were established well before water accumulated in the field from mid-June onwards. The late-sown crops (10 June), despite good initial germination, could not withstand immediate waterlogging. The tall variety, Utkalprabha, elongated faster with rising water level and escaped complete submergence; whereas the semi-dwarf Gayatri failed to withstand such extreme excess water stress. Application of N fertilizer up to 40 kg/ha proved beneficial to the crops sown by the end of May. However, with crops sown on 10 June, the application of N could not compensate for the loss in yield due to an inadequate initial crop stand. Therefore, early sowing of tall varieties by the end of May along with a basal application of N fertilizer is recommended for higher productivity of rice under excess water conditions.

Sixteen experiments over six seasons (1981–87) compared the growth and yield of up to 16 seed-tuber weights, ranging from 1–5 to 110–120 g, in one second-early and four maincrop varieties. Four of the experiments (1986–87) examined effects in seed tubers from seed crops planted in July; the remaining experiments used seed from crops planted at the normal time, April–May. Effects were similar for seed from the different planting dates. Plants from seed < 5 g (and occasionally up to 15 g) emerged slightly later and produced a smaller crop canopy that those from larger seed. The later emergence from the smallest seed was a consequence of a slower rate of sprout elongation. There were no effects of seed weight above 15 g on stem emergence or growth of the canopy. In 1982, a severe frost completely defoliated all plants in four experiments but within 2 weeks complete plant emergence was re-achieved from all seed weights except the smallest (1–5 g). The results suggest few differences between seed weights > 5 or 10 g in emergence from similar depths of planting or in recovery from frost damage.

Tuber yields were little affected by seed weight > 5 or 10 g, even at constant within-row spacings. Consequently, seed rates from 0·59 to 5·4 t/ha produced similar yields and the results suggest considerable economic benefits and potential for using seed tubers of much smaller weight than may be sold under current legislation. The use of small seed tubers from late-planted crops may result in further economies in production costs and reduction in disease in seed tubers.

Soils in farmlands near Ibadan, Nigeria, where shifting or continuous cultivation of cassava intercropped with maize is practised, were sampled in February 1990 and their characteristics compared with those of similar, uncultivated, forest soil. Organic matter, total nitrogen, exchangeable calcium, magnesium, potassium and sodium, cation exchange capacity and pH were lower in the cultivated soils. Continuous cultivation exerted a greater effect on soil organic matter, total nitrogen and available phosphorus status then did shifting cultivation. It is suggested that inorganic and organic fertilizers and mulch should be applied to cultivated soil to conserve the soil nutrients. Fallows of 3–6 years following 1–3 years of cropping appeared incapable alone of adequately restoring soil fertility. They should, therefore, be supplemented with fertilizer applications.

Incorporation of large amounts of straw (8–15 t/ha dry matter) into the soil had no effect on the incidence of soil pests and diseases or sugarbeet seedling population densities in experiments performed over three seasons (1984/85 to 1986/87) in Suffolk. Straw incorporation had no effect on sugar yield at the recommended rate of nitrogen fertilizer application, but the sugar yield and nitrogen uptake were reduced in one year by the incorporation of straw when the rate of applied nitrogen was low. It is probable that incorporating straw reduced the amount of nitrogen leached over the winter; however, the longer-term implications of straw incorporation remain to be assessed.

Experiments at the Experimental Station of the Agricultural University of Padova, Italy (45° 21′ N, 11° 58′ E) during 1985–89 evaluated poultry manure as a fertilizer. Two levels of fertilization (medium and high), using different mixtures of poultry manure and mineral fertilizers were compared with a non-fertilized control. The fertilization treatments were repeated each year on the same plots. All the crops tested responded strongly to fertilization, giving the following increases in yield (expressed as a percentage of the maximum yields): 30% for potato (Solanum tuberosum L.), 19% for sugarbeet (Beta vulgaris L. var. saccharifera L.), 82% for onion (Allium cepa L.), 85% for tomato (Lycopersicon esculentum Mill.) and 64% for spinach (Spinacia oleracea L.). The most effective fertilization formula varied with crop and year of cultivation. All the tested fertilization treatments had a similar effect on potato and onion, whereas the highest yields of tomato and spinach were obtained with a mixed fertilization at the highest rate of nutrients.

Poultry manure and mineral fertilizers at two rates of application (medium and high) and in different combinations, together with a non-fertilized control, were tested at the Experimental Station of the Agricultural University of Padova, Italy (45° 21′ N, 11° 58′ E) in 1985–89.

Compared to the control, all the fertilization treatments increased the incidence of larger-sized bulbs of onion and tubers of potato, improved the fruit colour of processing tomato and the raw protein content of spinach, but reduced the acidity and acids: soluble solids ratio of tomato and the dry matter content of spinach leaves.

In addition, the application of 140 kg/ha of N, 140 kg/ha of P2O5 and 100 kg/ha of K2O as mineral fertilizer or as poultry manure gave the best scores of processing suitability of potato, both for sticks and chips. All the fertilization formulae, except for 140 kg/ha of N, 140 kg/ha of P2O5 and 100 kg/ha of K2O as poultry manure alone, showed significant decreases in the extractable sucrose ratio in sugarbeet, compared with the control. In processing tomato, the best scores of suitability for paste transformation were obtained with mixed fertilization (1/3 poultry manure and 2/3 mineral fertilizers) applying 210 kg/ha of N, 210 kg/ha of P2O5 and 150 kg/ha of K2O and the plots receiving only mineral fertilizers produced fruits with less favourable values of pH and electrical conductivity compared to the poultry manured ones.

Potential rates of denitrification from two field soils, differing in past history, were measured by anaerobic incubation of fresh samples in a glasshouse maintained at 15–25 °C at ARC Letcombe Laboratory, Wantage, Oxfordshire in 1981. Nitrate was not limiting. The topsoils (0–20 cm) from both sites denitrified more than the subsoils (20–60 cm). The production of nitrous oxide was positively correlated with the carbon content of the soils while potential rates of denitrification in the two soils were similar. The total accumulated loss of nitrogen was greater from the soil with the greater organic carbon content. The use of acetylene showed that the denitrification losses were underestimated by measuring only nitrous oxide. N2O was still being reduced to N2 even after 100 h continuous exposure to acetylene.

Two crossbred wethers (c. 45 kg) and two Hereford heifers (c. 215 kg) were fitted with permanent cannulas in the rumen and abomasum and given a diet of lucerne hay and barley (60:40). Organic matter (OM) intakes were 0·67 kg/day for sheep and 3·14 kg/day for cattle.

The mean numbers of protozoa in the rumen fluid were 9·3 × 105/ml for sheep and 7·4 × 105/ml for cattle. 14C-labelled protozoa were prepared by incubating rumen fluid in vitro with [14C]methyl choline and then isolating them by sedimentation and differential centrifugation. The labelled protozoa were returned to the rumen of each of the donor animals in a single injection. The specific radioactivity in mixed protozoa isolated from the rumen was measured for 3 days. The protozoal pool size was 10 and 12 g N in the sheep and 64 and 44 g N in the cattle. Protozoal N contributed, on average, 48% of the total N in the rumen.

Production of protozoal N in the rumen was 9·5 and 11·2 g/day for the sheep and 49·5 and 38·6 g/day for the cattle. The flow of protozoal N from the abomasum was calculated to be 1·6 and 2·9 g/day for sheep and 17·3 and 13·3 g/day for cattle. Thus, on average, 79% of the protozoal N was recycled within the rumen of the sheep and 65% within the rumen of the cattle. Protozoal N made up 11–20% of total N flow from the abomasum. The turnover times of 14C-labelled protozoa injected into the rumen of the sheep and the cattle were similar (26·2 and 26·8 h for sheep; 30·8 and 27·5 h for cattle) and were similar to those for protozoa isolated from the rumen of sheep after direct intraruminal injection of [14C]methyl choline (28 and 36 h).

Dairy cows were inseminated on the basis of oestrus detection alone (Control, n = 206) or in conjunction with milk progesterone profiles (Experimental, n = 204). Milk samples were taken at 4–5 day intervals to determine oestrous cyclicity and on alternate days (at strategic times) to determine the time of ovulation. Progesterone profiles were consulted routinely as an aid to oestrus detection, and also to identify and aid diagnosis of cows with reproductive disorders. Cycling cows not observed in oestrus were inseminated on the basis of their progesterone profile alone. Animals showing oestrus within 2 days of a progesterone-timed insemination were inseminated again. In Experiments 1 and 2, inseminations were given from Day 42 post partum, but AI was delayed (mean time of 68±1·1 days after calving) in Experiment 3.

The median interval from calving to first insemination was not significantly different between Experimental and Control groups, but the time of conception was earlier (P < 0·05) and the median calving interval shorter (P < 0·05) in progesterone-monitored cows in Expts 1 and 3. In addition, the percentage of cows served within 21 days of the start of the service period was greater (P < 0·05) in Experimental groups in Expts 1 and 2. This was reflected by an increase in the proportion (P < 0·05) of cows pregnant by 85 and 100 days after calving. The frequency with which the interservice interval equated to the length of the oestrous cycle was increased (P < 0·01) by progesterone testing (84·1% and 53·9% in Experimental and Control cows, respectively). Conception rates did not differ significantly between groups, but the number of double inseminations (P < 0·001) and thus the mean number of inseminations/conception (P < 0·01) were greater in progesterone-monitored cows. Conception rate was lower (P < 0·05) in cows that failed to show oestrus, and to the first insemination in double-inseminated cows.

Progesterone testing reduced (by 44–66%, P < 0·01) the number of cows presented for veterinary examination and the mean time of presentation (P < 0·05), and also influenced the diagnosis made.

Lactating ewes, ewes that had lambed but subsequently lost their lambs (dry) and weaners were either artificially infested with 2000–3000 third-stage Haemonchus contortus larvae (parasitized) or drenched with levamisole (treated) and run under extensive grazing conditions in north-west Queensland. Worm egg counts in parasitized lactating, dry and weaner sheep ranged from 860–2830 eggs per gram of faeces. These levels of infestation significantly (P < 0·01) reduced liveweight gain of all three sheep classes, milk yield of ewes and wool growth of weaners compared to their treated counterparts. The lower milk yield of the parasitized ewes significantly (P < 0·01) reduced lamb growth rate. Survival of lambs to weaning was 26% higher in the treated group. The experiments showed that moderate levels of H. contortus, that did not produce clinical signs of infestation, reduce productivity of sheep in this semi-arid environment.

Five cross-bred Suffolk lambs (liveweight 24–29 kg) were fed lucerne silage and made acidotic or offered supplemental protein with the objective of determining the effects of acidosis and amino acid undersupply on food intake from silage. In this study, at McGill University, Quebec, Canada in January 1989, lucerne silage (25% DM) was supplemented with equimolar amounts (450 mmol/kg DM) of ammonium chloride, ammonium bicarbonate and sodium bicarbonate; fishmeal was added at 100 g/kg silage DM. The lambs were fed ad libitum according to a 5 × 5 Latin square with 21-day periods.

Digestibility of organic matter (OM) from silage ranged from 78 to 82% and was not significantly affected by diet (P > 0·05). Voluntary intake of digestible organic matter (DOM) from silage was . Fishmeal supplementation of lucerne silage improved nitrogen retention (P > 0·05) but not intake of DOM. The addition of ammonium chloride to silage reduced blood concentration (p < 0·05) and urinary output of HCO3, increased ammonia excretion in urine (P < 0·05), and depressed intake of DOM (P < 0·05). Ammonium bicarbonate also reduced voluntary intake of DOM (P < 0·05) but had no significant effect (P > 0·05) on the acid-base status of the lambs. Sodium bicarbonate depressed food intake but had no significant effect on measures of acid-base balance.

The results suggest that metabolic acidosis is not an underlying mechanism restricting food intake by sheep and that neither acid-base imbalance nor inadequate protein status is likely to explain the limitation in food intake from ensiled lucerne.