During three growing seasons (1980–3) the influence of sowing date (early September to mid-November) on the yield of winter barley (cv. Igri) was assessed. Delaying sowing resulted in a linear decrease in maximum grain yield at a rate of 0·43 % for every day sowing was delayed. Advancing the date of sowing increased the duration of preanthesis development, increased the level of tillering and hence ear density at harvest. Yield was linearly related to the resultant higher number of grains.

Three strains of Rhizobium able to fix nitrogen in symbiosis with lentils in saline soil were screened. Nodulation pattern, N2-fixation and grain yield were all influenced by Rhizobium strain and lentil genotype. Genotypes DL-443 and Pant L-406 were found to be more salt tolerant than others, and gave the highest grain yield.

Kinetic studies of thiaminase I in extracts of ruminant faeces showed that the affinity for one substrate varied with the concentration of the other substrate in the manner of a two-step transfer mechanism. When the alternate substrate concentration was optimal, the apparent Michaelis constant (Km) for thiamine was 176 μΜ and the apparent Km for aniline was 3·19 mΜ. It is recommended that in routine thiaminase assays, the thiamine and aniline concentrations should be at least 1·5 and 25 mΜ, respectively. When non-saturating concentrations of thiamine are used in thiaminase assays the results should be reported as unimolecular reaction constants since the enzyme activity can be calculated only if suitable Km data have been determined.

Improved radioactive and colorimetric thiaminase assays with saturating substrate concentrations gave similar results. The analytical variation of the colorimetric method was rather high but this method may be useful for laboratories which lack radioactive isotope facilities.

Thiaminase assays were performed on cultures of 14 species of rumen bacteria. Only Megasphaera elsdenii had thiaminase activity and its cosubstrate specificity was different from the rumen thiaminase associated with cerebrocortical necrosis in ruminants. It was concluded that the source of rumen thiaminase in that disease has yet to be identified.

The object of this study was to investigate the vegetative growth in six barley varieties grown in southern Spain (Granada) during 1979, 1980 and 1981. The results showed that crop dry weight (CDW) was dependent on environmental factors (mean temperature, rain, and radiation) which were the determinants of the two CDW components, leaf area index (LAI) and leaf area ratio (LAR). However, the effects of these climatic factors on crop growth rate (CGR) and on its components, mean leaf area index () and net assimilation rate (NAR), were partially obscured by ontogenetic drift. In addition, a highly significant relationship was demonstrated between CDW (when the LAI reaches its maximum value) and grain yield. This suggests that the pre-anthesis period has a great influence in the determination of grain yield variation in hot, dry areas, where photosynthesis is very limited after ear emergence.

Magnesium deficiency has been recognized to occur on acid (pH 5·5 or lower), sandy and highly leached soils or in soils whioh have received heavy application of fertilizers especially with materials which are lacking in magnesium or high in potassium (Berger, 1962; Foy & Barber, 1958). In addition to absolute deficiencies, induced forms can also occur, especially when K:Mg ratio in the soil exceeds 5:1 (Caldwell, Hooper & Little, 1968).

Nitrosoguanidine-induced mutation frequencies for resistance to streptomycin, spectinomycin, erythromycin and novomycin were studied in Azospirillum brasilense. Lentil inoculated with A. brasilense and its mutants and Rhizobium strains produced increased nodule dry weight, nitrogenase activity of nodules and roots and grain yield compared with an uninoculated control.

To increase the productivity of fields growing direct-seeded upland rice, which usually gives low yields because of weed competition, unsatisfactory establishment and exposure to intermittent drought, an experiment on intercropping of rice with blackgram was conducted in two seasons under rainfed conditions on a sandy loam soil. Blackgram, when intersown simultaneously in one row in every 30 cm wide space left between the stand of 10 cm apart paired rows of rice, reduced the yield of rice by 1·64 t/ha. When one row of blaokgram was intersown, 21 days after sowing of rice (after completing weeding) between the paired rows of rice, rice yield was reduced by only 0·24 t/ha compared with solecropping of rice with weeding. This system provided mean yields of 2·48 t/ha of riceand 0·95 t/ha of blackgram. The price of blackgram being high, it showed a mean monetary advantage of Rs. 2373/ha over sole cropping of rice. The blackgram reduced the weed population appreciably.

In view of the increase in micronutrient deficiencies in crop plants, ans attempt is made to group 57 Benchmark Indian soils into different micronutrient availability classes (clusters) vis-à-vis some soil characteristics. Since most of the soil characters are expressed in proportions or percentages (a usual practice in soil studies), the data matrix was transformed into log10 values to bring it nearer to normality. The transformed data matrix was used for cluster analysis and subsequently also for discriminant analysis. By following the method of Euclidean cluster analysis, the 57 Benchmark soils could be subdivided into three clusters. The distinctness of clusters was proven by distance-matrix as well as discriminant analysis. All the soils of cluster I and II originated from arid and semi-arid climates and these were alkaline in reaction, low in organic carbon (OC) and high in total lime. On the contrary, cluster III comprised all but a few soils from humid-subhumid regions. These soils were acidic in reaction and relatively high in OC and total lime. The soils of cluster I and II were poorer in diethylene triamine penta-acetic acid (DTPA) extractable micronutrient cations than those of cluster III. This study thus reveals that it is possible to classify diverse soils by statistical means into distinct clusters based upon micronutrient availability and associated soil properties. Furthermore, it suggests that soils of arid and semi-arid climates as a group, because of their low micronutrient availability, are expected to be more prone to deficiencies than those of humid and subhumid zones.

A field experiment, made during the rainy seasons oof 1982 and 1983 at the Indian Agricultural Research Institute, New Delhi, studied the effects of blending urea with dicyandiamide (DCD) on the yield and yield components of rice. DCD-blended urea was as effective as neem-cake-coated urea in respect of yield components as well as grain and straw yield of rice and when all the nitrogen was applied 10 days after transplanting both the materials produced significantly more grain and straw than prilled urea. Urea super granules (USG) were superior to DCD-blended, as well as neem-coated, urea.

In many instances soils are routinely air-dried and sieved prior to chemical analysis to permit ease of handling and decrease variability. Such drying, however, can increase the extractability of some elements, for example, the amount of P extracted by 0'5 m-NaHCO3 (Brookes, Powlson & Jenkinson, 1982). Much of the increased P is derived from soil micro-organisms killed by the soil drying (Brookes et al.1982). Similarly, much of the flush of C and N mineralization that occurs after rewetting of dried soils can be derived from killed soil micro-organisms (Jenkinson & Powlson 1976; Marumoto et al.1977; Marumoto, Anderson & Domsch, 1982).

Field and laboratory studies were carried out in 1981 and 1982 to investigate the relationship of stalk morphology and chemical composition to lodging resistance in maize in the rainforest zone of Nigeria.

Morphological characters correlated with lodging were plant height, diameter and length of basal internode, thickness of rind and weight of 5 cm basal section. Lodging was negatively correlated with grain yield, and with the percentages of total nonstructural carbohydrate, protein and potassium in the stalks. Premature stalk senescence and rot were common in varieties susceptible to lodging. Lodging had no relationship with leaf area and number of days from sowing to flowering.

Kura or Caucasian clover (Trifolium ambiguum Bieb.) is a perennial, rhizomatous legume indigenous to Caucasian Russia and adjacent regions (Kannenberg & Elliott,1962; Bryant, 1974). Those agronomic characteristics that lend it potential significance, namely an extensive root-rhizome system, winter-hardiness, resistance to numerous and serious clover pests, and the production of nectar-rich flowers, were enumerated by Parker & Allen (1952). These authors also pointed out that usage of kura clover was hampered by ineffective nodulation. However, in recent years commercial and effective inoculant preparations have become available. Consequently, it has been suggested that kura clover could have potential as a pasture legume and for soil conservation purposes (Bryant, 1974; Spencer et al.1975). Pertinent literature on kura clover is scanty. The present study evaluated the nutritional characteristics of kura clover relative to otherforage legumes.

Two groups of six sheep were fed either dried-grass or ground maize-based diets for at least 4 weeks before slaughter. Samples of the small intestinal mucosa and spancreatic tissue were assayed for a-amylase, glucoamylase, maltase and oligo-l,6-glucosidase.

The pancreatic tissue contained high activities of α-amylase and much lower activities of glucoamylase, maltase and oligo-1,6-glucosidase. There was no effect of diet on the specific activities of any of these enzymes in the pancreatic tissue.

The activity of α-amylase adsorbed on to the mucosa of the small intestine was greatest in the proximal region of the small intestine, the activity generally declining with increasing distance away from the pylorus. There was no diet effect on the absorbed α-amylase activity.

Similar patterns of distribution along the small intestine were observed for maltase, glucoamylase and oligo-1,6-glucosidase with the highest activities in t he jejunum. There was no overall effect of diet on glucoamylase or maltase specific activities and glucoamylase total activity, although the total activities of maltase and oligo-1,6-glucosidase were significantly greater for the sheep fed the ground maize-based diet (P < 0·05).

It is suggested that ruminant animals may be capable of digesting large amounts of starch in the small intestine through an adaptation in the activity of the host carbohydrases.

It has been found from controlled environment studies that high temperatures lead todepressions in milk production (Johnson, 1965; Hafez, 1968; McDowell, 1972). Under outdoor situations where all climatic variables may act simultaneously on the animal, responses may vary from the classical chamber studies.

Research conducted on sowing dates for wheat shows a trend towards increased yield as sowing is advanced (U.K.: Walker, 1980; Bingham et al. 1983; the Netherlands: Darwinkel, Hag & Kuizenga, 1977; Canada: Nass et al.1975; Briggs & Aytenfisu, 1979). In a review of the influence of drilling time on winter wheat in the U.K. McLean (1981) suggested October planting as the optimum. However, sowing before this time often results in increased yield (Bingham et al.1983).

Pollen grains of oil-seed rape, Brassica napus, were germinated in vitro in conditions in which water activity could be closely controlled. Germination success depended on the humidity experienced by the grains before contact with the germination medium, as well as on the osmolarity of that medium. On contact with the germination medium the grains swelled and then shrank. Each suffered one of three fates: it burst, or it germinated without bursting, or it did neither, remaining unchanged. Grains that were to remain unchanged swelled least. Those that were to burst swelled most. Those that were to germinate were intermediate.

Some implications for in vitro germination studies are discussed.