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Farmer-managed trials with browse trees were undertaken at two locations in southeast Nigeria. The fast-growing tree species Leucaena leucocephala and Gliricidia sepium were either inter-planted with crops as alley farms or planted in pure stands as intensive feed gardens. At both locations, most of the trees established successfully under farmer management. However, the quality of establishment was uneven, and the rate of utilization generally poor, especially at one site. The limited success of the trials is traced to a number of related sociological, institutional and edaphic factors. These include poor soil fertility; the incompatibility of established cropping patterns and rotation practices with the planting of trees on farms; the division of labour and organization of decision-making within the household; and land and tree tenure rules. It is argued that farmer-managed trials are necessary to reveal the importance of sociological and institutional factors in farmers' decision making, and that such trials require a high level of farmer autonomy in their management.
Observations that are frequencies rather than measurements often call for special types of statistical analysis. This paper comments on circumstances in which methods for one type of data can sensibly be used for the other. A section on two-way contingency tables emphasizes the proper role of χ2 a test statistic but not a measure of association; it mentions the distinction between one-tail and two-tail significance tests and reminds the reader of dangers. Multiway tables bring new complications, and the problems of interactions when additional classificatory factors are explicit or hidden are discussed at some length. A brief outline attempts to show how probit, logit, and similar techniques are related to the analysis of contingency tables. Finally, three unusual examples are described as illustrations of the care that is needed to avoid jumping to conclusions on how frequency data should be analysed.
Laboratory experiments and field tests were used to study the effects of seven anti-microbial agents and a trace element salt mixture (TEM) on the decay of cut pieces of seed potatoes. The effect of a mixture of gibberellic acid and ethrel (GA + E), TEM, and TEM with GA + E on the sprouting behaviour and yield of tubers was also studied. All the anti-microbial agents inhibited decay, although TEM and oxine were superior to other treatments. There was an increase in crop yield when seed tubers were treated with TEM. In laboratory tests, the GA + E mixture and TEM were effective in breaking dormancy.
Two bean genotypes differed in rate of root extension and elongation when grown under different soil water stresses in transparent tubes placed at an angle of 25°. Root intensity (the root length visible cm−2 of the viewing surface) gave a quick indication of the distribution of the total root length when screening cultivars for drought resistance.
Field studies of the dynamics of transformation and availability of applied phosphorus in a Vertisol cropped with rainfed cotton showed that phosphorus application increased available phosphorous in the soil. However, 70–80% of the phosphorus was fixed when more than 40 kg P2O5 ha−1 was applied. Maximum uptake of phosphorus by cotton occurred during the active growth period 40 to 80 days after germination, as reflected in a steep decline in the labile pool of available phosphorus in the soil. Over 50% of the total inorganic phosphorus occurred as Ca-P, which was the major contributor to the labile pool available to the cotton crop. The maximum response of cotton in terms of both dry matter and seed cotton and the maximum uptake of nitrogen, phosphorus and potash occurred when phosphorus was applied at 40 kg P2O5 ha−1. Phosphorus application increased the length, spread, volume and weight of roots.
Seed inoculation with Bacillus polymyxa markedly increased the yields of rice and chickpea crops, while Pseudomonas striata caused a greater impact on crop production when used with rock phosphate or super-phosphate in a wheat crop. The effect of the phospho-microbe inoculants was greater in phosphorus-deficient soils.
The growth of roots and shoots was measured in stands of groundnut grown at a number of populations on stored water in central India. Total weight and length of roots per unit land area increased with population density, but the proportional increases were much less than for shoot weight. Consequently the root:total weight ratio increased from 0.3 in the densest stand to almost 0.5 in the widely spaced crop. The denser stands produced a greater proportion of their roots at depth. In wide rows there was little change in rooting density across the inter-row space.
Total dry matter per unit land area increased with population, although the weight per plant was less in denser stands. Although the crops were harvested prematurely, pod yield per unit land area, unlike total dry matter, was no greater in dense stands than in more widely spaced crops. The greatest number of pods per unit land area was recorded at an intermediate population density.
Stands of groundnut were grown at four densities on water stored in a medium depth alfisol in central India. Evaporation was estimated from changes in soil water content, and partitioned between transpiration and evaporation from the soil surface. Seasonal transpiration was strongly influenced by plant population, and approached a maximum as the population density increased to 23 plants m−2. Evaporation from the soil surface was only a small component of the seasonal water balance in dense stands, and was little affected by planting density. Differences in transpiration rate between spacings were greatest early in the season, but diminished when the denser stands ran out of water. The denser stands extracted more water from deep in the profile. Plants in widely spaced rows preferentially extracted water from near the row; water mid-row was only used later in the season.
At a field site in central India, four populations of groundnut (Arachis hypogaea L.) were grown on stored water to investigate how the production of shoot and root dry matter is related to transpired water and intercepted radiation. Throughout the season, total dry matter was closely related to transpiration (slope = 3.0 mg dry matter g−1 water) and the amount of radiation intercepted by foliage (slope = 0.74 g dry matter MJ−1 radiation intercepted). Accumulated transpiration increased linearly with intercepted radiation at 0.37 kg water MJ−1 in the sparser stands. In the densest spacing, the initial slope of the relation at 0.28 kg MJ−1 decreased later in the season because water deficits curtailed growth without a concomitant reduction in the interception of radiation.
The objective of this paper is to identify the major factors responsible for the differences in transpiration rate (T) between stands of groundnut grown at three row spacings on stored water in central India. A method of analysis is developed to distinguish between the impact on transpiration of ground cover (which varied threefold between spacings) and of root:shoot ratio, which was substantially greater in the wider row spacings. When the soil was wet, both T and the canopy conductance, gc, were approximately proportional to the fraction (f) of incident radiation intercepted by foliage. But when the soil water content decreased below a threshold value, T/f and gc/f decreased because of an increase in stomatal resistance. Stomatal closure in response to soil water stress occurred sooner in the denser stands, partly because of more rapid depletion of soil water. A second contributory factor was that the sparser stands (which had a relatively large root:shoot ratio) had a greater capacity to keep stomata open as the soil water deficit increased.
Four forage bassicas, kale, rape, turnips and swede, and fodder beet were evaluated for adaptation to tropical highland conditions using small-plot experiments and field observations. In a short cropping season turnips were best adapted with a mean yield of 22 t ha−1. The crop was quick to establish and gave good ground cover. Kale and swedes were better adapted to a long season and yielded more than perennial forage grasses or maize. Yield was related to the length of growing season, exceeding 100 t ha−1 by about 250 days. Kale and swedes established poorly on soils high in aluminium. Direct sunlight appeared to damage swede roots, causing secondary soft rots. Rape showed no advantage over kale. Fodder beet failed to establish satisfactorily in any of the experiments.
Three species of lupin, three vetches and a soyabean were evaluated as green manures under tropical highland conditions. With moderate soil fertility and 150 days of rain, all lupin types and a locally obtained vetch gave yields of about 80 t ha−1 fresh material. Under less favourable conditions, low soil pH and high aluminium saturation, only Lupinus luteus achieved these yields. During the short season, with about 60 days of rain, the yield of L. luteus was reduced to 30 t ha−1 and establishment of the vetches was slow and they yielded poorly. Growth of soyabean was poor under cool conditions. Under fertile conditions, lupin grain yields of up to 5.2 t ha−1 were obtained in the long season but in the short season, yields were less than 1 t ha−1. Rhizoctonia solani was the major disease encountered.
The climates to which lentil (Lens culinaris) crops are exposed can vary appreciably depending on location and date of sowing. The effects on growth, development and seed yield when three USA cultivars experienced relatively warmer or cooler day/night temperatures during the vegetative period were investigated in growth cabinets. Plants were nodulated and supplied with either 20 or 80 ppm inorganic N; they differed appreciably in morphology and vegetative vigour, and so in their potential for subsequent pod production, depending on pre-flowering temperature and on nitrogen nutrition. Variations in seed yield were largely a consequence of treatment and cultivar effects on pod number per plant, and a pre-flowering temperature regime of 21°/7°C (mean 14.9°C) was supra-optimal. The pre-flowering environment clearly affects potential pod production and has persistent effects on the capability of plants to fill the pods produced.