A technique for observing the effects of soil physical and other factors on root growth was evaluated, using glass tubes packed with soil. The number of root intersections observed on a grid at the interface between the soil and glass was correlated with the number of root ends counted within the soil core. Comparatively small differences in the dry bulk density of a structureless sandy loam (1.25 and 1.50 g cm−3) had much larger effects than differential watering treatments on the pattern of root growth of lettuces (Lactuca sativa). Loosening the soil to depth (with additional fertilizer) increased the availability of water, under both wet and dry conditions, and improved water use efficiency, primarily through effects on root activity.

Field experiments during 1979 and 1980 on a Vertisol soil at ICRISAT Centre, Hyderabad, India, examined the residual effect of pigeonpea (Cajanus cajan) on growth and yield of a following maize crop. Pigeonpea was grown alone or as an intercrop with sorghum fertilized or not with 80 kg N ha−1. Sorghum alone and fallow treatments were included for comparison. In the first year, the sorghum/pigeonpea intercrop produced the largest grain and dry matter yields, but the yield of intercropped pigeonpea was about 50% less than that produced by the sole crop. Pigeonpea alone had a large residual effect on maize, increasing grain yield by 57% and total plant dry matter by 32% compared with corresponding values after fallow. In comparison, intercrop pigeonpea had little residual effect. Maize following either fallow, sorghum grown alone, with or without N, or the sorghum/pigeonpea intercrop, again with or without N, required fertilizer equivalent to 38–49 kg N ha−1 in order to attain yields similar to that of unfertilized maize following sole crop pigeonpea.

A study was undertaken to find out the nitrogen requirement of wheat (WH-157) when grown after various grain legumes on the sandy loam soils at Hissar (NW India). Yields of wheat were significantly increased when grown after black gram (110%), green gram (108%) and soyabean (41%) compared with those after pigeonpea. Preceding crops of green gram and black gram reduced the nitrogen requirement of a succeeding wheat crop by 30–60 kg ha−1, compared with only 30 kg ha−1 after pigeonpea or soyabean. Pigeonpea was least beneficial in this regard but a pigeonpea-wheat cropping sequence produced the maximum net profit.

The yields of eight grass species, Axonopus compressus, Brachiaria decumbens, B. humidicola, B. miliiformis, Dicanthium caricosum, Ischaemum aristatum, Paspalum conjugatum and Stenotaphrum secundatum, were compared at five sites under different coconut densities giving variations in shade. Light transmission (LT) values were approximimately 100 (adjacent open area), 70, 50, 40 and 20% of full sunlight. Soils were fertile, red-brown clays developed on uplifted coral limestone (typic arguidoll), with marginal K status. Brachiaria spp. yielded most in full sunlight, with B. decumbens giving 28 t ha−1 year−1. I. aristatum was less sensitive to shade than the Brachiaria spp., at least down to 40% LT. S. secundatum, although poor yielding at 100 and 70% LT, gave the best yield of all species at 20% LT. Shaded plants had thinner leaves and larger nitrogen concentrations than unshaded ones. B. decumbens and B. humidicola are recommended for open plantations (LT > 70%), I. aristatum for moderate shade (LT 45–70%) and S. secundatum for deeper shade (30–50%) on poor fertility soils.

Four cultivars of cowpeas (Vigna unguiculata L. Walp.) were grown in 15 sets of conditions (environments) i.e. in several monthly plantings in each of three years. Data for seed yield were analysed to investigate the effectiveness of using planting dates in preliminary yield trials of new cultivars. Extremely significant environment mean squares and wide ranges of environmental indices (− 13.3 to 23.5) and seed yield (11.4 to 48.2 g plant−1) indicated real differences among environments. Stability analyses of the cultivar × environment interactions suggest that, where limited funds preclude the use of several locations, monthly plantings for two or more years could be used effectively in the preliminary evaluation of cultivars without losing much information on their relative ranking.

A replicated field study was conducted during 1979 and 1980 in the Karnal district of Haryana, India to investigate the effects of three rates of gypsum (0, 5.2 and 10.4 t ha−1) on the performance of five forage grass species (Rhodes grass (Chloris gayana), blue panic (Panicum antidotale), Panicum laevifolium, Karnal grass (Diplachne fusca) and coastal Bermuda (Cynodon dactylon)) on an extremely sodic soil. The soils used had a large exchangeable sodium concentration and pH in the top 15 cm (94% and 10.6, respectively). For comparison, the same grasses were also planted in a normal soil. The results showed that the relative tolerance of these species to increasing sodicity was in the order of Karnal grass > Rhodes grass > coastal Bermuda > blue panic ≥ Panicum laevifolium.

Three cowpea cultivars were grown in the dry season on an inland valley swamp. Rice straw was used to mulch the plots and all seeds were pelleted with nitramolybdenum before planting. Fertilization with N, P and Mo and cultivar differences affected pod production and seed yield, but differences in plant population or inoculation with Rhizobium did not affect nodule weight, pod no. m−2, pod weight or seed yield significantly. Seed yields of 0.91 t ha−1 from an improved cultivar and 0.83 t ha−1 from the local type were obtained. Even with heavy mulching there could be variations in seed yield in undeveloped inland valley swamps because of changes in microrelief.

Thirty-two Prosopis accessions were studied and biomass production (dry matter) determined for 27 of them, which were irrigated when the soil moisture tension reached 60, 200, or 500 kPa. Three seasons after transplanting (i.e. after 2½ years) the trees were harvested, weighed, and sub-sampled for moisture content determinations. Little difference was observed in productivity among irrigation treatments. A 20-fold range in biomass productivity occurred among accessions; Prosopis chilensis (0009) from Argentina gave the greatest production of 13.4 t ha−1 a−1. The water use efficiency of US rangeland accessions ranged from 2300–2600 kg H2O kg dry matter−1. P. chilensis (0009) in the driest irrigation treatment had a water use efficiency of 345 kg H2O kg dry matter−1.