Maize silage was exposed to doses of y radiation varying from 0 to 6 Mrad inclusive and the effects of this treatment on the microflora and possible changes it might impose on the chemical composition were monitored. The highest dose was required to reduce the native population of micro-organisms to an insignificant level and only minor losses of lactic acid and ethanol were sustained. In addition, the irradiated silage was inoculated with representatives of groups of micro-organisms implicated in the aerobic deterioration of silage and the subsequent changes upon exposure to air observed. The inoculum proliferated and induced losses of fermentation acids, water-soluble carbohydrates, dry matter and, to a minor degree, neutral detergent fibre, and resulted in an increase in temperature and total nitrogen, the factors most likely to change during aerobic deterioration. Only the 6 Mrad dose yielded material suitable for investigations into the identification of those organisms primarily responsible for aerobic deterioration.

Three types of field instrument are described that are suitable for the automated and replicated in situ measurement of the soil properties: temperature, thermal conductivity and water pressure. Novel aspects of their design and construction are discussed, as are details of their installation and precautions necessary for successful use in the field. The principle of operation of each type of instrument is described and the method of controlling several instruments of the same type via a computer-based data acquisition system is indicated. Their accuracy and performance under field conditions are shown to be very adequate. Determination errors are approximately 0·1 K in the range 0–35 °C for temperature, 6–8% for thermal conductivity, and 1 mm water for water pressure, with a time constant of about 2 sec in a silty clay loam soil; reliability is measured as two sensor failures out of 236 over an operating period of several months. Examples are given of data collected during their deployment in an experiment to determine the physical effects of tillage on soil.

The influence of rest interval and grazing duration on herbage production of dryland lucerne (Medicago sativa L., cv. Hunter River) pastures was studied in a 6-year experiment on a black earth in subtropical southern Queensland. Rest intervals (R) of from 32 to 60 days were combined with grazing durations (G) of 4, 8 or 16 days, or with mowing (M), in the following treatments: (1) R32-4, (2) R32-G16, (3) R44-G4, (4) R44-G16, (5) R56-4, (6) R40-G8, (7) R36-M, (8) R48-M and (9) R60-M. Grazing was with sheep at a rate equivalent to 20/ha on a year-round basis. Amounts of dry matter of lucerne and of volunteer species on offer were measured prior to grazing or mowing, and some measurements of the residue remaining after grazing were made. Chemical composition of representative lucerne samples was also determined.

Mean total amount of lucerne on offer declined from 10·8 to 7·2 t/ha/year between the first 2 years and the last 2 years, whereas total amount of volunteer species, principally grasses, increased from 3·0 to 18·2 t/ha/year over the same period. This difference was partly due to lower utilization of volunteer species. The decrease in amount of lucerne was due to loss of plants, and treatment effects arose through differences in the degree to which amounts from individual surviving plants increased to compensate for stand thinning. Concentrations of mineral elements in lucerne were always above critical levels for plant and animal growth.

Treatment R40-G8 maintained the largest amounts of lucerne on offer to the end of the experiment, with treatments R32-G4 and R32-G16 then having least. Large amounts of grass were associated with 4-day grazing, and to a lesser extent with short rest periods. The results confirm the need for a minimum rest period between grazings in a subtropical environment and also show the need for grazing to control excessive grass growth as well as lucerne if lucerne productivity is to be ensured. Some requirements which would lead to more successful management of lucerne in the subtropics are discussed.

Data from three dairy-cow nutrition experiments have been analysed in terms of the yields of milk, lactose, fat and protein. Yields of the three constituents varied linearly with milk yield. However, yields of fat from individual cows were much more variable at high milk yields than were the other two constituents. Patterns of feeding had relatively little effect on the pattern of protein yield in cows fed to their production potential but could be important in influencing yields of fat.

Predicted responses of protein and fat yields to increments of feed were generally small in cows being fed according to their predicted yield potential and the conversion of metabolizable energy to milk constituents was of a low biological efficiency.

During 1973–8 six field experiments examined the effect of 0, 41, 82, 124, 166 and 207 kg N/ha with and without irrigation on the growth, yield and quality of sugar beet. The culture of the crops was planned to produce a large yield in order to determine the optimal nitrogen application for the above-average crops which many growers are now seeking to produce. Ammonium nitrate was used as the nitrogen source, broadcast in one dose before sowing as was recommended practice in the early 1970s. The growth of the crop was monitored from the seedling stage to harvest in December, as was nitrogen uptake by the crop, and water removal from the soil using a neutron probe.

In 3 years when the weather was dry after drilling, the fertilizer significantly depressed the number of plants which established but plant weights showed that some nitrogen fertilizer was needed early for rapid seedling growth. Changes in the method of applying fertilizer for sugar beet are therefore suggested and are being tested. Soil analyses in the plough layer during establishment (May–June) indicated an optimum concentration of mineral nitrogen of about 40 mg N/kg soil at this stage.

Nitrogen fertilizer was very important for a high yield; throughout the growth of the crop it greatly increased total dry-matter yield and at final harvest this was reflected in sugar yield. Considering the six years together, sugar yield was linearly related to both dry-matter yield and total nitrogen uptake. However, within a year, increasing nitrogen uptake above 200 kg N/ha with nitrogen fertilizer did not increase sugar yield; maximum yields of sugar each year were normally obtained with 125 kg N/ha fertilizer or less, and irrigation had little effect on the optimum amount. Explanations for the lack of responsiveness of sugar beet to greater applications of nitrogen fertilizer are being sought in further more detailed analyses of the crop and its environment.

Four bruchid-susceptible and four bruchid-resistant cow-pea cultivars were crossed to produce 16 F1s and their reciprocals. From each cross, six generations, P1, P2, F1, F2, BC1, BC2, were obtained. Each cross was fitted to the additive-dominance model. Estimates of additive and dominance variances were obtained from the half and full sib analyses of the F1s and their reciprocals respectively. It was demonstrated that resistance to cow-pea weevils has additive, dominance and maternal components.

A pot experiment was made to study the effect of green manuring and iron application on the pE, pH, Fe concentration and iron equilibria in a calcareous and a noncalcareous soil. Green manuring drastically decreased the pE and pH and increased the Fe concentration of the equilibrium soil solution to a greater extent than submergence alone. Addition of Fe decreased pE, pH and increased Fe concentration both with and without green manuring. In calcareous soil pE and pH were high and Fe concentration was low compared with non-calcareous soil. In the absence of green manure and added iron, although there were wide variations in pE, pH and Fe concentration, Fe(OH)3-Fe2+; Fe3(OH)8-Fe2 + and Fe(OH)3-Fe3(OH)8 systems were controlling the solubility of Fe after 1 week of submergence in both the soils. But on green manuring all the above systems in calcareous soil and only Fe(OH)3-Fe3(OH)8 system in non-calcareous soil were operating at 1 week of submergence and continued afterwards. Addition of iron, with and without green manure, failed to bring an appreciable effect on these systems in calcareous and as well as in non-calcareous soil.

Use of generalized lattice designs instead of complete block designs in 244 cereal variety trials grown in the U.K. since 1975 has resulted in an average reduction of 30% in variances of varietal yield differences. The lattice designs were most effective when the number of varieties was more than 50 but worthwhile reductions in variance, averaging about 24%, were obtained in trials with fewer than 20 varieties. The data also provide guidance on the choice of block size and the potential for improvement by neighbour methods.

Field experiments made for 4 years between 1976–7 and 1979–80 in a semi-arid environment of north-west India showed that the productivity of dryland unirrigated wheat can be increased considerably by adjusting the date of sowing to conducive atmospheric temperatures. Sowing in the middle of November when daily mean temperatures ranged between 19 and 21 °C produced yields ranging between 2·6and 3·5t/ha (averaged over the 4 years) compared with 1·4–3·3 t/ha obtained from the crop sown by mid-October when the daily mean temperature ranged between 24 and 26 °C. The tall cultivar C 306, a derivative of winter x spring wheat cross, could withstand sowing at higher temperatures (mid-October) more than the spring wheats. High temperatures prevailing during the seedling stage of spring wheats shortened their vegetative growth and initiated early differentiation. Night temperatures above 13 °C coupled with day temperatures of 33–35 °C in the last fortnight of October adversely affected the tillering of spring wheats sown on 15 October and produced smaller spikes with few fertile spikelets.

Studies were conducted to evaluate the effect of 50% restriction of normal daily water intake on nitrogen balance, plasma urea concentration and excretion of different urinary nitrogenous constituents (ammonia, creatine, creatinine, urea and undetermined nitrogen) in the Marwari breed of sheep of the Rajasthan desert, India. The results indicated that the reduction in feed intake in water-restricted sheep leads to a reduction in intake and excretion of nitrogen through faeces (P < 0·01) and urine (P < 0·01) of these animals. No sigficant differences in the excretion of most urinary nitrogenous constituents between ad libitum watered and water-restricted animals were observed, except for creatine which was excreted in significantly higher concentrations in the urine of the water-restricted animals. On offering water ad libitum for 3 days to the restricted animals, the plasma urea in these animals dropped from 33·0 to 20·7 mg/100 ml, i.e. almost to the level in the animals watered ad libitum (18·7 mg/ 100 ml). The daily dry-matter intakes of the ad libitum watered and restricted animals were 790 and 488 g, respectively. The digestibility coefficients for dry matter and crude protein of the feed were 47·1 and 27·2%, respectively in ad libitum watered and 56·6 and 39·5%, respectively, in restricted animals. This improvement in the efficiency of digestion in water-restricted sheep may not be due to any enhanced microbial activity in the rumen, but may possibly be due to an increased absorption of feed nutrients in the hind gut of these animals.

The soils of on area around Llangadog (mid-Wales) have been systematically sampled on a grid basis at 0–8 cm and 30–35 cm depths.

A P-sorption index was determined for these samples as were Fe and Al extractable by both 0·1 M K-pyrophosphate solution and 0·2 M-NH4-oxalate solution at pH 3. The reactivities of the soils with 1 M-NaF solution at pH 6·8 and pH 8 were also measured.

The results were stratified in terms of parent material, soil classification at subgroup level and soil series, and correlation coefficients calculated between the P-sorption index and the other variables (singly and in combination).

Only pyrophosphate-extractable Fe, i.e. ‘organically bound’, correlated reasonably well with the P-sorption index. However, the correlation was such that tolerably good estimates of P-sorption in an agronomic context could be made from pyrophosphate-extractable Fe values only for previously uncultivated brown podzolic soils (Manod series).

Fluoride reactivities at both pH values were poor predictors of P-sorption in these soils. Fluoride reactivity at pH 6·8 and oxalate-extractable Al, which have both been proposed as indices of the amounts of ‘poorly-ordered’ Al compounds in soils, failed to group these soils in similar ways. Doubt exists therefore as to whether these variables are measures of the same (or similar) property in these soils.

The seeds of a dwarf variety of pigeon pea (cv. Cita-1) were sown at 2, 4, 6 or 8 cm depths in three field trials in 1981 and 1982, in order to evaluate the effect of sowing depth on seedling emergence and the subsequent growth, development and yield of the crop.

In all trials, sowing pigeon-pea seeds deeper than 4 cm led to 1–2 days delay in seedling emergence, resulted in only 40–68% seedling emergence, reduced the development of the various growth and yield characters of the plant and significantly reduced seed yield. In two trials, plants from 4 cm sowing performed better than those from 2cm sowing in terms of development of growth and yield characters indicating that shallow sowing of pigeon pea prevents rapid and proper plant establishment.

The results therefore indicate that the optimum sowing depth for pigeon pea is 4 cm under the prevailing lowland humid tropical conditions.

In two field trials in 1982, the seeds of pigeon pea (cv. Cita-1) were planted at three configurationsof0·6 x 0·2m;0·4 x 0·3 m and 0·35 x 0·35m(on 14 April and 24 June)giving the same projected population density of 83 000 plants/ha for each configuration, in order to evaluate the best planting configuration for maximum productivity of the crop.

In the first trial, the 0·35 x 0·35 m configuration developed the highest magnitude of vegetative characters whilst the 0·4 x 0·3 m configuration had the highest number of seed-bearing pods, although seed yield was similar in all the treatments. In the second trial, the 0·4 x 0·3 m configuration developed the highest magnitude of growth and yield characters and thereby out-yielded the other two configurations.

The results show that in the early planting of pigeon pea, population density per se is most important in determining seed yield whereas planting configuration also becomes important in late planting where plant size is reduced as a consequence of the prevailing local conditions.

Five selections of Stylosanthes guianensis var. guianensis with a short-day flowering response were grown at three sites at altitudes of 10, 280 and 1000 m on the island of Bali, Indonesia at latitude ca. 8° 30′ S. Mean site temperature was ca. 6 °C lower at the highest site whilst mean short-wave radiation was lowest at the intermediate site.

Date of 50% floral initiation (FI) varied from 1 February to 21 June, when daylength (sunrise to sunset plus half civil twilight) decreased from 12·85 to 12·00 h. FI was independent of site for cv. Graham and cv. Cook, but at 1000 m it was 14 and 77 days earlier for cv. Endeavour and cv. Schofield respectively relative to the 280 m site. Little flowering of cv. Schofield occurred at 10 m, and it is suggested that cool temperatures promoted an increase in the critical photoperiod for this cultivar, or that warm temperatures inhibited flowering. FI was delayed at 1000 m in CPI 34906.

The duration of the phase from FI to flower appearance (FA) varied from 29 to 75 days according to selection and to site, and was negatively related to mean temperature, radiation, and maximum temperature for cv. Graham, cv. Cook, and CPI 34906 (but not for cv. Endeavour). Number of nodes at FA in this determinate species generally reflected growing conditions in the pre-flowering phase and was positively associated with age at FA in plants of particular varieties.

The effects of N, P, K and Na silicate fertilizers, and drought on the concentrations of K in the dry matter and tissue water of field-grown spring barley crops have been investigated. Percentage K in dry matter depended on the amounts of N, P, K or water received by the crops and was linearly related to fresh weight to dry weight ratio, but the slope of this relationship depended on whether or not the crops received K. Expressing K concentrations on the basis of tissue water eliminated differences between crops, except for those given insufficient K. Barley crops given fertilizer K maintained K concentrations in their tissue water of about 200 mmol/kg tissue water for most of the growth period but crops grown without K had only 50–70 mmol/kg tissue water. The results indicate that K concentrations in the tissue water are a more reliable indicator of tissue K status than % K in dry matter.

Decreases in crop K content resulting from poor K supply were balanced by increases in Na and Ca (but not Mg) contents so that total cation concentrations in the tissue water were similar in low and high K crops. The extra Na and Ca are probably primarily involved in maintaining charge balance for anion absorption but once in the plant they may also substitute for K in its osmotic role.

The analysis of two experiments involving the response of bread-making wheat to application of nitrogenous fertilizer is discussed. It is shown that a step function is required to determine the amount of applied N which optimizes the profit to be obtained from the crop. Varieties varied in their yield response to N and in the amount of applied N at which the ‘step’ took place and it is argued that trials of varieties at a common rate of N application or the reporting of results which are averaged over a number of rates cannot lead to very precise recommendations for growers.

A variety of factors influence the voluntary intake of ruminants including reticulo-rumen fill or distension (Campling & Balch, 1961; Welch, 1967; Grovum, 1979) and rate of passage of digesta through the gastrointestinal tract (Bines & Davey, 1970). The exit point of the reticulo-rumen, the reticulo-omasal orifice, potentially serves as a control site in regulation of particle movement from the rumen.

However, little definitive information on the functional behaviour of this anatomical location is available. Therefore, a fibre-optic endoscopic technique was designed to allow visual observation of the reticulo-omasal orifice in conscious, fed cattle.

America, New Hyde Park, NY) and a 35 mm camera (Olympus 0M-2N with 1–9 focusing screen) was attached. Photographs were taken at a shutter speed of 1/30 or 1/60 sec. The film used was Kodak (ASA 160) tungsten balanced slide film. Prints were generated from slides using the Cibachrome P30 process. An Olympus CLK-3 cold light source, having a colour temperature of 3200 °K, provided the illumination for projection through the endoscope. Opening and closing of the reticuloomasal orifice were photographed using this procedure.

Seed production of five selections of Stylosanthes guianensis var. guianensis was studied in Bali, Indonesia (latitude 8° 30′ S) with a series of harvests at three sites of increasing altitude and rainfall: (1) Sesetan, 10 m, (2) Kuwum, 280 m and (3) Pekarangan, 1000 m. Seed yield of cv. Graham, CPI 34906, cv. Cook and cv. Endeavour was maximal at Sesetan with yields of 109, 39, 38 and 166 g/m2 respectively, whilst cv. Schofield, which flowered little at low altitude, produced 12 g/m2 at Pekarangan. Optimum time of harvest varied from 26 April for cv. Graham at Sesetan to 1 November for cv. Schofield at Pekarangan. Yield stability over sites was greatest in cv. Graham, in which increased number of florets per spike at high altitude partially compensated for negative altitudinal effects on spike density. Disease reduced yields of cv. Cook and cv. Endeavour at Kuwum and Pekarangan and the incidence of rainfall at advanced stages of crop development reduced spike density and seed maturation.

It is suggested that the high seed yields attained at the low altitude, low latitude Sesetan site were attained via (1) vigorous vegetative growth and a longer duration of floral induction resulting in high bud site density, (2) high bud site fertility, (3) high seed set (ca. 70–80%), (4) high seed weight and (5) little or no disease or insect damage. The greater synchrony of flowering at higher latitude sites may be less critical for high levels of seed production than the greater length of crop development available at low latitudes.

Singh & Taneja (1978a, 6, 1981) have reported on several aspects of salinity tolerance in Indian desert sheep breeds, for example, maintenance of body weight, feed and water intake, body water compartments and blood characteristics. No report is available in the literature on the effect of varying levels of salt intake from drinking water on reproductive performance in these animals. The earlier reports on salinity tolerance in sheep have been almost wholly based on the animals' response to different levels of sodium chloride in synthesized drinking waters. It is, however, generally agreed that the upper limit of total salt tolerance in sheep depends not only on the concentration of the most abundant salt constituent in the drinking water (usually sodium chloride), but also on the concentrations of the other constituents. Divalent cations (calcium and magnesium) and anions (sulphates and carbonates) in the water are believed to be more toxic than the monovalent cations and anions (sodium and chloride).

The effect of field layout and the orientation of seed-production blocks on outcrossing rates was investigated in Indian mustard. The study incorporated three male:female combinations, i.e. 1:2, 1:3 and 2:4 laid in east–west, north–south and circular directions. The experimental material consisted of four test cultivars (RLM 198, RLM 514, Varuna and TM 4) in a split-plot design. Male sterility was achieved by spraying 0·25% (v/v) ethrel twice before the emergence of the first flowering shoots. The proportion of hybrid seed set was maximal in the 2:4 combination in a circular design. Outcrossing varied from 19 to 79%. Heterosis was evident in yield trials, but F1 hybrids showed carry-over effects due to ethrel treatment. It is argued that ethrelinduced male sterility has only a limited role in screening parental combinations for their yield assessment.