Crosses between two cultivars of tomato (Lycopersicon esculentum Mill.), and two accessions of the wild species L. pimpinellifolium (Jusl.) Mill, were made and F1, F2 and backcross generations were developed and studied. Significant differences in number of fruits per plant, yield per plant and fruit weight were found between means of the different generations. Variation in number of fruits per plant and yield was also found between plants within generations. Number of fruits per plant was a highly heritable character (average h2 = 73·6%) and closely correlated with yield per plant, indicating that it may be a suitable selection criterion for yield improvement in tomato crosses.

Field experiments were conducted in wet seasons (June-December) for 4 years on a clay loam Haplaquept, to study the effects of different N management practices on yield, urea and ammonium-N in flood water and N nutrition of an clite rice cv. CR 1009, grown in rainfed lowlands. During the first 3 years of the experiment, fertilizer management practices like band placement of neem-cake-coated urea (NCU), broadcast application of sulphur-coated urea (SCU) at sowing, or point placement of urea supergranules (USG) 3 weeks after germination at 40 kg N/ha gave grain yields of 3·1–3·4 t·ha, which were almost equal to that of split application of prilled urea (PU). In the 4th year of the experiment, besides NCU and USG, single dose applications of PU as band placement, incorporation in the soil at sowing or broadcast incorporation of soil-treated urea at early tillering was also found to have similar effect on grain yield and N uptake as split application of PU. The flood water of the treatment receiving broadcast application of PU at tillering contained some urea and ammonium N, which rapidly decreased to negligible amounts in 3·4 days.

The results suggest that, depending upon the feasibility, any one of the single dose application methods at sowing time or 3 weeks after germination may be adopted in this system of rice culture, which avoids top-dressing of PU to surface flowing flood water of greater depths at later stages of crop growth.

Carbofuran at 1·5 kg a.i./ha applied around the seeds during sowing in spring controlled lucerne stem nematode and Sitona damage to lucerne and increased herbage yields in the susceptible cv. Europe. Such treatment was also beneficial to Europe in soil not infested with lucerne stem nematode and to the ‘resistant’ cv. Euver sown in infested soil. Subsequent treatment of the soil in spring each year with thiabendazole did not enhance lucerne yield but aldicarb at 1·5 kg a.i./ha watered onto the stubble and hydraulic or electrostatic sprays of carbendazim, thiabendazole hypophosphite, thiodicarb, dimethoate or pirimiphos methyl applied to new foliage after each herbage harvest lessened stem nematode injury and increased herbage yields in one experiment but had less or no effect in another.

Under conditions of semi-deep water (51–100 cm) rice varieties with greater plant height produced more dry matter and grain yield as N fertilizer was increased from 0 to 20 and 40 kg/ha. The varieties which performed better in a situation of slow rise in water level to a depth of 120 cm could not survive a quick rise in water level owing to their lesser plant height and elongation ability. The loss of dry matter (dead and dried leaves) was also greater in varieties susceptible to deep water than varieties tolerant of deep water.

With the increase in N fertilizer, there was increase in plant height, number of tillers, dry-matter production and grain yield. The loss of dry matter was less in crops given N fertilizer than in those not given N fertilizer. The varieties capable of producing higher grain yield in response to N fertilizer under semi-deep water did not improve their grain yield under intermediate deep water (15–50 cm). With increase in application of N fertilizer from 0 to 40 kg/ha the N concentration in grain increased. N concentration did not vary in straw under intermediate deep water, there was no definite trend in semi-deep water, and it was higher under conditions of semi-deep than intermediate deep water.

The results of 173 field experiments carried out between 1957 and 1986 are presented comparing ammonium nitrate and urea as top-dressings for winter cereals and grassland.

The trials show that urea was an inferior nitrogen source to ammonium nitrate. The yield from ammonium nitrate was significantly greater than that from urea for winter wheat, winter barley and for first, second and third cut silage. The results suggest (a) that winter wheat and winter barley respond differently to the two nitrogen sources and (b) that yield losses from urea are just as likely on first cut silage as second or third cut.

A breakdown of results according to soil texture, soil pH and region showed no consistent differences in yield loss. This indicates that broad generalizations based on soil characters and geographical location are not helpful in distinguishing situations where urea performance may be either better or worse than average.

Soil disturbance caused by a slant-legged subsoiler (Trade name, ‘Paraplow’) and the duration of its effect was investigated in an experiment comparing long-term direct drilling with shallow tine cultivation and mouldboard ploughing. The ‘Paraplow’ significantly reduced soil strength, measured by cone resistance, to the depth of cultivation (33–35 cm) for up to 20 months, after which soil recompacted. The ‘Paraplow’ increased the volume of soil with cone resistance < 1·5 MPa by 52% within its working depth, compared with an equivalent depth of undisturbed soil. Contour diagrams of cone resistances clearly illustrate the patterns of soil loosening caused by the ‘Paraplow’.

Measurements on soil cores (73 mm diameter × 50 mm) show that the ‘Paraplow’ did not appear to increase significantly the volume of macropores (> 60 μm) in direct-drilled soil, nor did it reduce the bulk density in the top 5 cm as effectively as the mouldboard plough.

The root density of spring barley, measured at the beginning and end of tillering, was significantly increased within the horizon disturbed by the ‘Paraplow’ but below the depth of loosening there were no differences. This improvement of root growth probably resulted from an increase in the number of large pores (which could not be measured adequately in the soil cores), as well as the reduced soil strength. Better drainage of the soil loosened with the ‘Paraplow’ suggested that macroporosity was improved. The need to sample large volumes of soil to detect changes in bulk density and macroporosity is stressed.

The dry-matter digestibilities of 13 important herbaceous and browse forages from an arid rangeland in north-western Kenya were evaluated in a comparative in vitro trial using rumen fluid from indigenous sheep, goats, a camel, and Merino sheep kept at an agricultural laboratory. All inoculum donors had varied diets preceding the experiment, but little substantial difference was observed in the ability of each fluid to digest test materials. Tt was concluded that the Merino sheep inoculum provided an adequate substitute for inocula from indigenous animals for studies of the nutritional ecology of free-ranging livestock.

Relationships between slaughter weight, side weight, linear carcass measurements, carcass joints, carcass composition, and prediction equations for carcass composition have been established for Sudan Desert lambs.

Of the carcass linear measurements, chest depth had the highest coefficient of correlation with slaughter weight (r = 0·62) and side weight (r = 0·64) followed by the circumference of the buttocks with correlation coefficients of 0·49 and 0·63 respectively.

Correlation coefficients between percentage tissue in the side and percentage tissue in the different joints showed that percentage lean in middle neck and shoulder, leg and best end, in this order were strongly associated with percentage lean in side (P < 0·001). Percentage bone in middle neck and shoulder, leg and loin was positively associated with percentage bone in the side. Fat in leg and best end neck gave a significant correlation (P < 0·001) with percentage fat in the side.

Trivariate regression equations for prediction of carcass composition were calculated for both sexes in the two breed types and the best end neck joint was found to be the best practical predictor with R2a (adjusted coefficient of determination) of 0·81–0·98 for lean prediction and 0·70–0·92 for fat prediction.

Data from 11 sugar-beet crops grown at different sites, in different years and with some variations in husbandry have been used to re-examine the process of dry-matter partitioning. Two-phase linear models did not describe adequately the distribution of dry matter. There was no evidence of a discontinuity in the partitioning between root and shoot at any point in crop development. It is suggested that, contrary to a recent view, events in the shoot, rather than the storage root, largely determine how dry matter is allocated between growth and sugar storage.

The mineralization kinetics of nitrogen in acid soils, and their modification by the addition of an organic fertilizer (cattle slurry), were studied by incubating a humic cambisol for 36 weeks using a method based on that of Keeney & Bremner (1967). The cumulative curve of the quantity of nitrogen mineralized in soil not given fertilizer departs significantly from Stanford's theoretical model, which predicts linear dependence of nitrogen mineralized upon √t. The observed kinetics are interpreted as due to the superposition of two mineralization processes involving different substrates.

The cumulative mineralized nitrogen curves for soil samples enriched with the various slurry fractions likewise reflect complex kinetics involving at least two main substrates. Consideration of the net mineralized nitrogen shows that F,, the solid fraction with the highest C/N ratio, clearly induced immobilization of nitrogen during the first 130 days of incubation, and analysis of the NO3/NH4 ratio suggests that this immobilization was probably at the expense of nitrate. F3, the liquid fraction, first induced a brief period of mineralization and then stabilized nitrogen levels, giving rise to a reduction in net mineralized nitrogen. The addition to the soil of F2, the semi-liquid fraction, produced results intermediate between those of the other two fractions.

In conclusion, the increase in organic nitrogen in the soil after addition of cattle slurry depends in the short term on the liquid and semi-liquid fractions, whereas long-term effects involve both the stable residues of these fractions and the more solid fraction. The labile fraction of the pool of mineralizable N benefits more than the recalcitrant fraction, and the time constants of the mineralization process are reduced.

The phenotype of medium duration pearl millet varieties grown in West Africa differs from that of the shorter duration millets grown in India. African varieties are usually much taller, have longer panicles, fewer productive tillers, and a lower ratio of grain to above-ground dry-matter (harvest index). The effect of crop duration on plant phenotype was investigated in two hybrids using extended daylengths to increase the duration of the vegetative phase (GSl: sowing to panicle initiation). The two hybrids, 841A × J104 and 81A × Souna B, were considered to represent the Indian and African phenotype, respectively. Tiller production and survival, leaf area, and dry-matter accumulation and partition, were monitored over the season. Grain yield and its components were determined at maturity.

The two hybrids responded similarly to the short and long daylength treatments. The duration of GSl was increased from 20 to 30 days, resulting in increased number of leaves, leaf area, and stem and total dry-matter accumulation; there was no effect on tiller production and survival, or on panicle growth rate. Grain yield was, therefore, the same in both GSl treatments, and harvest index (HI) was much reduced in the long GSl treatment owing to the increased stem growth. One evident effect of a longer GSl was on dry-matter partitioning between shoots; partitioning to the main stem (MS) was increased, whereas partitioning to the tillers was reduced.

There was no difference in crop development, growth or yield between the two hybrids in either GSl treatment. The only significant differences were in the efficiency with which intercepted radiation was converted to dry matter, which was greater in 841A × J104 than in 81A × Souna B, and in the balance between MS and tillers; the grain yield of the MS was significantly greater in 81A x Souna B than in 841A × J104, but at the expense of number of productive tillers.

The results demonstrate that both African and Indian phenotypes are equally productive under good agronomic conditions. The lower HI in longer duration African millets is a consequence of a much extended stem growth phase and therefore increased competition between stem and panicle during grain filling. Possible ways to increase grain yield in the medium duration African millets are considered.

The results of a long-term field experiment conducted from 1977 to 1984 on alluvial (Ustochrept) soil of Jalandhar showed positive responses of the crops to N. The responses of potatoes to N were reduced by farmyard manure (FYM), green manure of dhaincha and moong and the responses to the organic manures were also reduced by N. The N responsesof potatoes were, however, not affected by the N applied to preceding maize. FYM was better than the green manures in augmenting total tuber yield, large-grade tuber yield and K concentration in the plants.

The N applied to the potatoes showed significant residual effect on succeeding wheat crops, reducing its optimum dose of N by about 50%. The residual effect of N on wheat was highly correlated with nitrate status of the soil. The organic manures applied to potatoes improved the yield of the succeeding wheat but did not differ from each other.

The fodder crop of pearl millet raised after 7 years also indicated the superiority of FYM to the green manures. There was a build-up of organic carbon, N, P and K in soil and the build-up was maximal with the use of FYM. The application of N had no effect on the organic carbon and nitrogen status of the soil. N improved the availability of P but decreased that of K.

Under intermediate deepwater (15–50 cm) conditions, sulphur-coated urea (SOU) drilled behind the plough at sowing was superior to other coated (neem, lac, coaltar) urea materials and broadcast incorporation of prilled urea in increasing the yield of direct-sown rice. In transplanted rice, the grain yield was highest with urea super granules (USG) placed 30 days after transplanting (DAT) followed by SOU broadcast incorporation at planting. N-use efficiency increased considerably with SCU drilled behind the plough or USG placed 20 days after sowing in shallow standing water in direct-sown rice and SCU broadcast incorporation or USG placed 30 DAT in transplanted rice.

Laboratory and glasshouse experiments were conducted to study P release kinetics and uptake of P by wheat (Trilicum, aestivum L.) in ten benchmark soils of Punjab (India). Phosphorus desorption, determined by successive extraction with 0·01 m-CaCl2 solution, was lower in calcareous soils (group I) than in non-calcareous soils (group II). Desorption of surface P in soils followed pseudo-first-order kinetics. The values of the kinetic constant of desorption and the radial diffusion coefficient of P increased with the amount of added P in soils.

A significant linear relationship between cumulative desorbed P and both dry-matter yield and P uptake indicated that the rate of release of P from the solid matrix is important in determining P uptake by wheat crop. Phosphate uptake was less dependent on the initial solution P concentration than on the rate of phosphate release.

This paper describes a comparison of acid insoluble ash (AIA) and acid detergent lignin (ADL) ratio techniques for estimating digestibility with the conventional total collection method using sheep fed a range of feeds. In only two of 17 digestibility trials were the results obtained by AIA ratio techniques significantly different from those obtained by the total collection method. In the case of ADL no significant differences occurred between the results obtained by the ratio technique and total collection method.

In a trial using sheep in metabolism cages the AIA and ADL contents of faeces excreted in consecutive 4 h periods covering 48 h did not show any significant variation either within or between the two 24 h periods.

The results obtained from ‘grab’ samples of faeces (25–40 g) taken per rectum or from faeces bags attached to sheep fed communally can be expected to give acceptable agreement with total collection provided the marker concentration in the faeces represents a number of sheep sampled on several days, since variation between individual samples of faeces may be high.

Six nitrosoguanidine-induced manganese-resistant mutants of Azospirillum brasilense were isolated and used for associative N2 fixation studies with cheena (Panicum miliaceum L.) in acid soil. Three mutants showed cross-resistance to aluminium and neomycin, but of these three only one showed cross-resistance to streptomycin. Inoculation of cheena with A. brasilense and its mutants at different rates of applied nitrogen led to a significant increase in associative N2 fixation, N content, dry-matter production and grain yield in acid soil. A saving of about 20 kg N/ha could be achieved by inoculating seeds of cheena with these mutant strains in acid soil.

Statistical equations were derived for estimating three soil moisture constants, i.e. field capacity (FC), wilting point (WP) and available water capacity (AWC), from soil saturation percentage (SP), which is an easily determinable parameter. The regression equations were evaluated from a data set obtained on 438 soil samples collected from different horizons of 111 profiles of the Indogangetic Plains in northern India, having a wide variation of texture and other physico-chemical properties. The three soil moisture constants were positively correlated with logarithms of SP (r = 0·985 for FC v. In SP, 0·979 for WP v. In SP, and 0·914 for AWC v. In SP). The regression equations were thetested on an independent set of experimental data on 57 samples collected from 14 representative soil profiles of the study area. Values of the three moisture constants of this data set, predicted from the regression equations, were in exceptionally good agreement with the observed values. The mean estimation error (the error of the estimated value relative to the measured value) was only 0·55% for FC, 0·12% for WP and 0·67% for AWC.

High-temperature-adapted strains RAU 1, RAU 2 and RAU 3 of Azospirillum brasilense C 7 were isolated from stepwise transfer to higher temperature (30 to 42 °C). One of the strains (RAU 1) showed more growth, greater nitrogenase and hydrogenase activities at 30 and 42 °C than parental and other temperature-adapted strains. This strain also showed growth and more nitrogenase activity from pH 6·5 to 8·0. Strain RAU 1 showed cross-resistance to penicillin (300/µg/ml) but not to streptomycin, kanamycin, viomycin and polymixin B at 30 and 42 °C. It was demonstrated in field plots in calcareous soil that seed inoculation with RAU 1 enhanced mineral uptake of cheena. Inoculation with RAU 1 led to a significant increase in associative nitrogen fixation, dry weight of roots, grain and straw yield of cheena compared with the uninoculated control with or without applied N, but the effect of seed inoculation with high-temperature-adapted strains was variable with different genotypes of cheena.

The relationship between germination rate within a carrot seed lot and subsequent seedling performance was studied in four seed lots of different viability. Seedling performance was assessed using slope tests conducted under controlled conditions and in the field following fluid drilling under a range of environmental conditions. Germination rate within a seed lot was positively related to vigour measured by slope tests, percentage emergence and seedling weight, and was negatively related to the spread of emergence times (In variance days) and the coefficient of variation (c.v.) of seedling weights. Sowing seeds selected as fast germinating resulted in greater seedling emergence percentages over a range of environmental conditions than when sowing seeds selected as slowly germinating.

The percentage (P) of incident photosynthetically active radiation (PAR) reaching the ground was measured in winter wheat crops throughout the season, and related to projected area index (L) of leaves, plus sheaths and stems when present. Between unfolding of the first leaf and appearance of the flag leaf the mean value for the exponential extinction coefficient (K) was 0·46±0·007. The value did not vary with the growth stage of the wheat and was scarcely affected by experimental treatments, apart from effects resulting from the presence of senescent tissues that intercepted light but whose area was not included in L. After anthesis, in crops having between 340 and 540 ears/m2, between 68 and 89% of incident PAR penetrated to below the ears. Relation between the further penetration to the base of the crop canopy and the area of green plus senescent leaf and stem tissue gave K = 0·50. The relation did not change significantly between anthesis and complete senescence.

The relation between P and L was similar whether P was obtained from instantaneous measurements made near midday, 24 h integrals of PAR or percentage ground cover measured photographically.