Soil instability, as measured by the dispersion ratios of the reclaimed salt-marsh soils of ca. 70 km2 of north Kent, was assessed on samples taken from 0–15, 35–50 and 70–85 cm depths from sites at the intersects of a 250 m square grid or along transects. The dispersion ratios were related to other soil properties including exchangeable sodium, potassium and magnesium percentages, organic carbon content, calcium carbonate content and electrical conductivity. The dispersion ratio correlates most closely with exchangeable sodium percentage and organic carbon content; weaker correlations exist with exchangeable potassium and calcium carbonate contents. Dispersion ratios rise sharply, i.e. reflect a marked increase in soil instability, when organic carbon content is less than 2·5% and calcium carbonate content is less than 2%. Magnesium has little effect on the dispersion ratio. The soil solution salt concentration (as expressed by electrical conductivity) is too low over much of the area to promote flocculation, and hence stability, of the soil clays.

Two experiments were carried out to determine endogenous excretion of purine derivatives in steers and lambs, and to investigate the relationship between microbial nucleic acid input and urinary excretion of purine nitrogen.

The endogenous excretion of allantoin after conversion of hypoxanthine, xanthine and uric acid to allantoin, was calculated to be 72 and 26 mg/kg W0·75 per day in steers and lambs, respectively, when the dietary protein contained no nucleic acid nitrogen.

The excretion of purine derivatives increased linearly with increasing microbial nucleic acid input in lambs. The excretion of purine derivatives in excess of endogenous contribution was closely related to the theoretically expected values. The average recovery was calculated as 0·96 for one sheep and 1·0 for the other.

Elimination of the rumen anaerobic fungi from sheep fed chemically-treated barley straw diets resulted in elevated proportions of propionic acid in rumen liquor (from ca. 0·15 to 0·30). Subsequent inoculation of these sheep with a pure culture of fungus decreased propionate concentrations within 3 days to the levels observed in control animals that possessed abundant fungal populations throughout the experiment.

Confirmation that propionate itself was not responsible for the elimination of the fungi was provided by the results of a second experiment in which intraruminal infusions of propionic acid failed to reduce fungal growth or prevent recolonization in sheep previously rendered fungi-free.

In a third experiment with sheep fed untreated barley straw, monensin supplementation produced the well known elevation of propionate concentrations. However, this treatment also resulted in the elimination of rumen anaerobic fungi from the animals. The magnitude of the increased concentration of rumen propionic acid, resulting from the elimination of the anaerobic fungal flora, indicates an important role for the fungi in the fermentation of high-fibre diets. In addition, these findings indicate that the well known elevation of propionate levels produced by monensin may likewise be effected directly by removal of the rumen anaerobic fungi.

Two field experiments examined the effects of nitrogen fertilizer, irrigation frequency and three wheat varieties on the yield and quality of irrigated wheat on a heavy clay soil. In the first experiment, with irrigation supplied to all plots at mid-tillering and close to ear emergence, there were negative effects of nitrogen fertilizer on grain yield with the reverse occurring with grain protein. The variety Songlen had one of the highest grain yields combined with higher milling yields and flour protein. In the second experiment, yield was maximized with at least two irrigations, whilst increasing irrigation frequency reduced flour protein and dough development time. While WW15 gave the highest yields irrespective of nitrogen or irrigation treatments, this variety had the lowest flour protein. With only one irrigation or without irrigation, nitrogen fertilizer increased grain protein; more frequent irrigation reduced mean flour protein.

Efficiency of N contained in some modified urea fertilizers was studied for wetland rice grown in an alkaline, low organic matter Fatehpur loamy sand (Typic Ustipsamment) soil having an average percolation rate of 109 mm/day. In the four field experiments, sulphurcoated urea (SCU) produced significantly more rice grain than urea supergranules (USG) or divided applications of urea or ammonium sulphate. Application of SCU at 58 kg N/ha yielded as much rice grain as was produced by divided application of urea at 116 kg N/ha. The N uptake data suggested that SCU-N was more efficiently translated into grain yield than urea N. Granular (7-day release rate 19%) and forestry (7-day release rate 29%) grades of SCU were equally effective. However, application of half the N basally through SCU and the remaining half top dressed as urea failed to outyield all urea divided in three applications. The indigenous coated materials, rock-phosphate-coated urea and urea gypsum, also did not perform better than divided urea applications as these did not possess a 7-day release rate less than 95%. Urea supergranules placed in the reduced zone of the soil could not come to the level of divided application of urea or ammonium sulphate. The N uptake data indicated that USG-N was correspondingly inefficiently utilized by rice. When the deep placement aspect of USG was combined with slow-release properties of SCU in the form of sulphur-coated urea supergranules (SCUSG), the performance of this product was inferior even to the divided application of urea. Undissolved or partially dissolved granules of SCUSG could be recovered even after the harvest of the crop.

The moisture use pattern and efficiency (MUE) of four barley cultivars (two hulled and two hull-less) were studied when the crops were grown in winter under unirrigated conditions at Varanasi, India, with different rates of application of nitrogen fertilizer. Increase in moisture use with age of the crop due to vegetative growth was recorded. Influence of varieties on consumptive use of water was found to be negligible except in the 1st year between 65 days after sowing and after harvest of the crop, when differences were due to differences in duration of the crop growth and rainfall which was received at the time of maturity. The moisture mining capacity of the barley crop from the profile (up to 120 cm) was increased with increase in the rate of nitrogen application. MUE of barley cultivars closely paralleled the grain yields, being more with hulled cultivars than hull-less ones. Higher MUE of barley was observed in the 2nd than in the 1st year of experimentation because of a better distribution of rainfall and moisture availability at the time of sowing, which boosted yields. Nitrogen application increased both yield and MUE of barley.

Two experiments were conducted on two varieties of Corchorus olitorius(‘NHCo 6’ and ‘NHCo 7’). The first one was on the effect of density of planting on their growth and development whilst the second was on the best planting ratio for Corchorus-tomato intercropping.

There was no significant difference in morphological characters of the two varieties. The maximum value of leaf area index for the two varieties was around 3. Maximum marketable and edible yields were obtained for the two varieties at 30 × 5 cm (666600 plants/ha) and the best time for harvesting was 44 days after sowing.

The best planting ratio for Corchorus-tomato intercrop was 2 rows of Corchorus and 1 row of tomato for maximum edible yield of Corchorus but for maximum economic returns, the best ratio was 1 row of Corchorus to 2 rows of tomato.

Field experiments on efficiency of fertilizer N applied as calcium ammonium nitrate (CAN) and urea to no-tillage maize (Zea mays) were conducted under humid (Onne) and subhumid (Mokwa) conditions. At both the locations the rate of N was 150 kg/ha.

A comparison of apparent crop recovery of applied N indicated that CAN was a more effective N source than urea under subhumid conditions (Mokwa) but that urea was more effective under humid conditions (Onne). In 1981, percentages of applied N recovered by the maize crop at Onne were 28 and 50% from CAN and urea, respectively, whereas the recovery at Mokwa was 46 and 34%, respectively. Total recovery by crop and soil (0–120cm) of CAN at Onne with divided application was equivalent to that at Mokwa with single application at planting (54%). However, the total recovery of urea was much lower at Mokwa (40%) than at Onne (60%). The results in 1982 followed similar trends. Excessive N leaching loss from CAN under humid conditions and volatilization loss from urea under subhumid conditions are considered to be the reasons for poor efficiency of fertilizer N.

Sheep were exercised on a treadmill to study the effect of increased energy demand on roughage intake and ruminal characteristics.

The experiment consisted of a pre-exercise period during which exercise sheep walked for 30 min/day at 2 km/h against a gradient of 0° followed by a full exercise period during which they walked a total of 9 km/day at 3 km/h against a 10°gradient during six daily sessions of 30 min each. Control sheep received no exercise but were treated similarly to exercise sheep in all other respects.

The mean values obtained during the pre-exercise period for the exercise and control groups and during the full exercise period for the exercise and control groups respectively were 1347, 1125; 1177 and 1114 g/day for organic matter (OM) intake; 956, 921; 803 and 848 g for rumen OM contents; 11·8, 13·6; 12·2 and 12·3 h for rumen retention time of water; 17·5, 20·2; 16·8 and 17·6 h for rumen retention time of fermentable OM; 27·3, 28·2; 26·4 and 26·7 h for rumen retention time of unfermentable OM and 46·9, 48·1, 44·4 and 45·9 kg for empty body weight. Only the decline in OM intake from pre-exercise to full exercise period differed significantly between exercise and control groups.

It is concluded from these results that an increase in the difference between energy demand and supply per se is not responsible for the apparent increase in the upper limit to OM accumulation in the rumen and concomitant increase in roughage intake observed during other situations of increased energy output such as lactation and severe cold.

A 2-year field study indicated that pearl millet yielded more when sown after fallow, cow pea and green gram than after maize. Preceding fallow, cow pea and green gram reduced the nitrogen requirement of pearl millet by 40 kg/ha compared with maize. Pearl millet responded linearly up to the highest rate of nitrogen (80 kg/ha). N applied to millet had no residual effect on the subsequent crop of chickpea. The chickpea yield followed the order fallow > green gram ≥ cow pea > maize. Chickpea responded to phosphorus up to 40 kg/ha. Green gram-pearl millet-chickpea proved the most profitable cropping sequence. Continuous cropping and application of nitrogen and phosphorus improved the organic carbon and available phosphorus but decreased the available potassium status of the soil.

The genetic parameters controlling the expression of seed yield and the yield components have been studied using both generation mean and triple test cross (TTC) analyses in two crosses of field pea. From generation mean analysis, it is obvious that in addition to significant estimates of additive and dominance components, epistatic components of mean [(i) and (I) types] were also important and duplicate type of epistasis was predominant for all the traits in both sets of crosses. In the TTC analysis, the major genetic component of variance was the additive component, though the dominance component was also found to be significant. There was evidence of epistasis for most of the characters studied. In fact, the overall epistasis (i type) was the major component of epistasis, but the parameter F was found in the non-significant range. The mean performance of the characters studied was higher in randomly-mated biparental progenies (BIPs) but there were more desirable transgressive segregants in the TTC population. Thus the genetic information obtained from both analyses seems to be complementary rather than alternative modes of inheritance in governing the expression of these useful economic traits.

A microplot experiment was conducted for two consecutive years, 1978–9 and 1979–80, on alkaline calcareous soils of Chittor, Kapasan, Nimbaheda and Chhotisadari blocks at the Department of Agronomy, College of Agriculture, Udaipur (India). It was found that soil application of 250 kg S/ha both of elemental sulphur and gypsum significantly increased chlorophyll a and b and concentrations of N, K and S of plants. Leaf sap pH and P and Fe concentrations were, however, significantly reduced by sulphur treatments. Foliar application of 0·2% Fe-EDDHA increased chlorophyll a and b and caused marginal increase in N concentration of plants. K and S concentrations remained unaffected but P and Fe concentrations underwent significant reduction. Leaf sap pH was not at all affected by this treatment.

Failure of metabolic translocation of iron and hence its inactivation inside the plant is suggested to be the most probable cause for the incidence of chlorosis despite high tissue Fe concentration. Sulphur application created a balanced nutritional environment and thus kept iron physiologically active for chlorophyll synthesis. Reduced efficacy of Fe-EDDHA might be due to high P concentration in the plant.

The effect of a slant-legged subsoiler (Trade name, ‘Paraplow’) on the growth of two crops of winter wheat following an intensively grazed grass-clover ley was investigated in 1981–2 and 1982–3. The treatments for the first crop were direct drilling, loosening the soil by shallow cultivation before drilling, loosening by ‘Paraplow’, and a combination of ‘Paraplow’ and shallow cultivation. For the second crop these treatments were repeated and a fifth added, loosening by ‘Paraplow’ after drilling. Seed was sown with a triple disk direct drill and all treatments received the same quantity of fertilizer.

Soil compaction was measured with a cone penetrometer in the autumn of 1982 and spring 1983; root axes were counted and dry-matter weights of shoot, grain yield and components of yield obtained.

Loosening soil by ‘Paraplow’ did not increase significantly the number of roots nor was the uptake of water by the crop in dry periods affected, even though soil strength, measured as cone resistance, was considerably reduced.

Shallow cultivation increased grain yield in the first wheat by 0·34 t/ha (P< 0·05) but had no effect on the second wheat. The ‘Paraplow’ did not increase yield of the first crop but the mean response of 0·65 t/ha in the second crop was significant (P < 0·05). Using the ‘Paraplow’ before or after drilling gave similar yields. Increases in yield were produced by more grains per unit area, not increased 1000-grain weights.

It is concluded that the apparently compacted soil did not restrict the growth of wheat and that the beneficial effect of the ‘Paraplow’ in the second crop was probably due to better drainage in the wet spring.

A comparative study of sorption maxima (simple and double Langmuir equations) and buffer capacity of acid soils was made in order to select the most useful P-sorption parameter. Data were obtained from 20 acid soils from Galicia (north-west Spain) and selection was made by linear and multiple regressions among sorption parameters, and between these and some soil characteristics related to phosphate sorption (clay and organicmatter content, pH in NaF, and 0·5 M-CuCl2-extracted Al).

The phosphate buffer capacity, determined by the slope of the regression ‘sorbed-P v. logc’, was the best parameter to represent soil phosphate sorption behaviour. 0·5 M-CuCl2- extracted Al was the edaphic characteristic which best related to sorption properties.

All combinations of four harvesting treatments and two sowing dates were comparedin each of 3 years in field experiments near Nicosia. In two of the years, different levels of applied nitrogen were compared. The harvesting treatments were: (1) a milk-stage cut,(2) a boot-stage cut and a regrowth cut, (3) a grazing-stage cut and a regrowth cut, and(4) three grazing-stage cuts and a regrowth cut. The sowing dates were (1) normal (12 November) and (2) early (15 October), with sufficient irrigation to ensure establishment. There was almost no response to applied nitrogen, evidently because of high reserves of available nitrogen in the soil. Early sowing reduced by 20 days the time taken to reach the stage at which the first node appeared, but increased, by 36 days, the length of time between the first node and the milk stage. Early sowing increased yield when the firstcut was at the grazing stage, but reduced yield when the first cut was at the boot or milk stage. At the grazing stage, the proportion of green leaf blade and the concentrations of nitrogen and nitrate-N were relatively high (means 74, 4·0 and 0·13% respectively) and digestibility was moderate (mean D-value 61). By the boot stage, green leaf, nitrogen and nitrate-N, but not digestibility, had declined (means 21, 1·8, 0·02 and 63 respectively). By the milk stage, green leaf, nitrogen and digestibility, but not nitrate-N, had declined further (means 3, 1·5, 48 and 0·05 respectively). Fully dead leaf blades were 28 units less digestible and 3·2 percentage units lower in nitrogen concentration than emerging leaves. Half dead leaf blades were higher in nitrate-N than fully expanded, fully green blades. 'Stem’ declined greatly in nitrogen concentration, but relatively little in digestibility, between the grazing and the boot stage.

Crops cut once or three times at a grazing stage recovered well, although theretended to be some reduction in the number of tillers compared with an undefoliated crop.

An experiment to measure the variation in the phenological and apical development ofwinter wheat (cv. Avalon) in England and Scotland is described. Ten sites which ranged from Aberdeen (57·2° N), the most northerly, to Newton Abbot (50·6° N), the most southerly, were included in the survey, and at each site seed was hand-sown in mid-September, October and November 1983. Developmental stages and sampling procedures were precisely defined to ensure uniformity in scoring by the observers at each site. Temperatures during the growing season were in line with the long-term means, though spring was cooler at all sites and summer warmer at most. The range of monthly-mean temperatures between sites was about the same as the difference between consecutive months. The method of analysis of development rates and durations was in terms of thermal time, modified by sensitivity to photoperiod and a vernalization requirement that slowed early development until a number of days of low temperatures had been experienced. In general, crops at northern sites developed more slowly than those in the south and particularly the south-west of England. There was less variation in the timing of apical stages for later sowings. Developmental rates responded linearly to temperature and photoperiod, with the base temperature increasing for later phases of development. The effect of photoperiod in modifying the rate of development was apparent for all developmental phases from emergence to anthesis, longer days accelerating development, but there was no effect on the duration of the grain-filling period. Vernalization exerted its effect solely within the phase from emergence to double ridge, and had a major influence on the variation between sites only for the first sowing.

The initiation of leaf and spikelet primordia was studied at sites ranging in latitude from Newton Abbot (50·6°N) to Aberdeen (57·2°N) in crops sown in the middle of September, October and November 1983. The rate of primordium initiation tended to decrease from south to north but there were also marked differences between quite close sites.

The rate of leaf initiation increased with temperature but photoperiod had little effect; the rate of spikelet initiation was affected both by temperature and by photoperiod. There were differences in the total number of leaves initiated which were only partlyexplained by differences in vernalization.

Expressing leaf and spikelet initiation rates in terms of thermal and photo-thermal time respectively showed a constant rate of leaf initiation and a constant and more rapid rate of spikelet initiation.

The effect of insect pollination on plant development and seed yield of winter oil-seed rape, cultivar Jet Neuf, was investigated by comparing plots caged with a honeybee colony, plots caged to exclude insects and plots uncaged and 'open-pollinated' by naturally occurring insects. Plants in the bee-pollinated plots finished flowering earlier, showed more advanced pod growth, and were shorter than those in the plots without bees. Pods from the plots with honeybees contained more seed post-flowering than those from plots without honeybees but the proportion of them that grew into mature seeds for harvest was determined by water availability during seed growth.

The computer model described simulates changes in soil mineral nitrogen and crop uptake of nitrogen by computing on a daily basis the amounts of N leached, mineralized, nitrified and taken up by the crop. Denitrification is not included at present. The leaching submodel divides the soil into layers, each of which contains mobile and immobile water. It needs points from the soil moisture characteristic, measured directly or derived from soil survey data; it also needs daily rainfall and evaporation. The mineralization and nitrification submodel assumes pseudo-zero order kinetics and depends on the net mineralization rate in the topsoil and the daily soil temperature and moisture content, the latter being computed in the leaching submodel. The crop N uptake and dry-matter production submodel is a simple function driven by degree days of soil temperature and needs in addition only the sowing date and the date the soil returns to field capacity, the latter again being computed in the leaching submodel. A sensitivity analysis was made, showing the effects of 30% changes in the input variables on the simulated amounts of soil mineral N and crop N present in spring when decisions on N fertilizer rates have to be made. Soil mineral N was influenced most by changes in rainfall, soil water content, mineralization rate and soil temperature, whilst crop N was affected most by changes in soil temperature, rainfall and sowing date. The model has so far been applied only to winter wheat growing through autumn, winter and spring but it should be adaptable to other crops and to a full season.

The model was validated by comparing its simulations with measurements of soil mineral N, dry matter and the amounts of N taken up by winter wheat in experiments made at seven sites during 5 years. The simulations were assessed graphically and with the aid of several statistical summaries of the goodness of fit. The agreement was generally very good; over all years 72% of all simulations of soil mineral N to 90 cm depth were within 20 kg N/ha of the soil measurements; also 78% of the simulations of crop nitrogen uptake were within 15 kg N/ha and 63% of the simulated yields of dry matter were within 25 g/m2 of the amounts measured. All correlation coefficients were large, positive, and highly significant, and on average no statistically significant differences were found between simulation and measurement either for soil mineral N or for crop N uptake.

A study of cross-bred ewes sired by Cambridge, Border Leicester and Lleyn rams out of Welsh Mountain ewes, involving a total of 408 observations, was carried out partly under lowland and partly under upland conditions in North Wales. The results snowed that the Cambridge and Lleyn were more precocious than the Border Leicester (relative percentage of ewes put to the tup lambing at 1 year old was 51·9, 66·3 and 66·8 respectively for Border Leicester, Cambridge and Lleyn cross-breds). In terms of lambs born and lambs reared per ewe lambing the ranking of the breeds was (in descending order) Cambridge, Border Leicester and Lleyn respectively. The Cambridge was lower in terms of mean weight of lambs at birth and at 56 days and relative mean age at slaughter tended to be lower in the Border Leicester crosses. Taking into consideration the lower body weight, particularly of the Lleyn cross-breds, ranking on relative feed conversion efficiency was Cambridge, Border Leicester and Lleyn when ewe fertility and days to slaughter were excluded.