This study, quantifying variation in flower and pod production in lentil (Lens culinaris), aimed to answer the question: Will selection for more pods per inflorescence increase seed yield? In Season 1 (1992–93) all open flowers were tracked to maturity in a field experiment with two lentil genotypes sown on two dates. Genotype Talia 2 had a higher rate of flower abortion than pod abortion, in contrast to genotype ILL 2581 which showed the reverse. Flower abortion accounted for 15% of flowers opened in early sowing and increased to 22% in the late sowing. Pod abortion was 19% (of flowers opened) in early sowing and 23% in the late sowing. These are the first quantitative estimates of flower and pod abortion in lentil. From the data, a rapid sampling method was developed to estimate the average number of pods per inflorescence at maturity. In Season 2 (1993–94) an experiment was conducted at two locations to estimate the average number of pods per inflorescence of 81 genotypes and to relate this to seed yield. Although the broad-sense heritability (h2) of the number of pods per inflorescence was 0.68 and its phenotypic correlation with seed yield was r = 0.71, the highest-yielding genotypes were not those with the most pods per inflorescence. Selection for the number of pods per inflorescence cannot be recommended for increasing seed yield in lentil.

Tea (Camellia sinensis) clones (PC113 and SFS204) sensitive to very dry air and clones (PC114 and SFS150) that are tolerant, were studied at two tea estates (Tshivhase and Grenshoek) in the Northern Province of the Republic of South Africa. Among the morphological leaf traits studied, stomatal density, pore diameter and pore depth were not linked consistently to stress tolerance. Cuticle thickness was not a good indicator of stress tolerance because genetic differences between clones were confounded by the clonal response of wax production to stress. In contrast, measured leaf conductance to water vapour transport was larger and leaf water potential was lower in sensitive clones, but only with more severe atmospheric stress (Grenshoek). Also the ratio of the calculated maximum stomatal conductance in old and young leaves was higher in sensitive clones, suggesting that the loss of a larger fraction of the total stem flow by old leaves enhanced the stress experienced by the young leaves. However, this indicator was valid only under the more stressful microclimate of Grenshoek. The results indicate that even promising criteria for stress tolerance should be tested by exposure to stress during selection.

Six genotypes of lentil (Lens culinaris) were grown in pots in a glasshouse under natural photo-periods of 10–12 h, extended to an inductive photoperiod of 16 h by supplementary illumination from incandescent lamps. The illuminance of the supplementary light was varied by placing replicate pots at different distances from the lamps; it decreased geometrically with distance (i.e. down an illuminance gradient) from about 2000 lux directly beneath the lamps to about 40 lux at a distance of 6 m from them. All genotypes came into flower progressively later as illuminance decreased; those selected in northern temperate regions were especially sensitive, taking about twice as long to flower at an illuminance of 40 compared with 2000 lux. We suggest, however, that these quantitative responses do not reflect differences in sensitivity to illuminance per se, but are the consequences of genotypic differences in sensitivity to photoperiod. The implications of these data are discussed in terms of adaptation to the aerial environment and strategies for screening germplasm and plant breeding in lentils and other grain legumes.

The Land Equivalent Ratio (LER) concept is presented and interpreted. Several different intercropping systems are considered and the need for methods to evaluate them is discussed. A general form of the LER is proposed for the evaluation, in particular, of a system that combines two intercrops having different yield proportions. Appropriate LER curves, obtained by varying the yield proportions, are used to compare different intercropping systems, and the importance of this approach is discussed.

Crop yield on continuously cultivated tropical forest soil was maintained at a fairly high level by the application of mineral fertilizer. Although the low rate of nitrogen applied as ammonium sulphate did not increase yield, there was a significant effect on pH of the soil resulting in a reduction of the divalent cations on the exchange complex. The effect of mulch was mainly chemical through the release of nutrients.

Differences in the growth and development of five genotypes of chickpea (Cicer arietinum) were studied until the three branch stage (18 or 21 days after sowing). Seedlings were grown in nutrient solution in clear Perspex cells immersed in temperature controlled water baths. Daily removal and photographing allowed serial measurements of the rate of root extension to be made. An accurate, detailed description of the rooting pattern was obtained by sectioning along the primary axis after harvest. Significant differences between the genotypes in root and shoot growth were recorded. The Syrian local landrace, ILC 1929, and the Ascochyta blight resistant genotype, ILC 428, had faster rates of extentions of the primary root axis and of lateral root development than the other genotypes. The possible significance of these results to subsequent growth and yield in Mediterranean environments is discussed.

A series of population density and row spacing trials were carried out with sorghum in conditions of increasingly severe water stress from 1980 to 1984. In conditions of reasonable water availability, increasing density resulted in increased leaf area indices, dry weight production and grain yields. In conditions of severely limiting water availability, increasing density resulted in developmental delays, density-dependent mortality and reduced plant dry weights, with little increase in dry weight production per hectare. In these conditions grain yields were reduced by increasing density. The proportion of dry weight allocated to grain declined with increasing density and decreasing plant size, a consequence of the requirement for a minimum plant size to support grain production. When plant size was reduced below a critical range, disproportionately large reductions in grain yield resulted.

Optimum densities for grain production varied from below 10 000 plants ha−1 in dry conditions to over 120 000 plants ha−1 in moist conditions. Medium density treatments produced the largest grain yields on a long term basis, but the low density treatment showed a reduced risk of crop failure and greater yield stability.

Close spacing between and within rows significantly increased the biological and agricultural yields of cowpea without exerting clearly differential effects on the three test cultivars of different forms. It is suggested that low yields of cowpeas commonly observed in southern Nigeria could be due largely to low planting density. A six-fold increase in yield of beans can be achieved by halving the current spacing of 90 by 30 cm. provided the crop is protected from field pest damage.

An experiment has its origin in the need to find answers to stated questions. From the start great care is given to its correct conduct (e.g. the application of treatments and the method of recording) as well as to statistical design, always with the original questions in mind. The analysis of its data is the climax of a long process and the questions to be answered must dominate all else. It is not enough to feed data into a computer package in the hope that it will provide an automated path to a true interpretation.

Where the treatments have been chosen with care to answer specific questions, the statistical way of designating purpose is to declare ‘contrasts of interest’, each corresponding to a degree of freedom between treatments. They derive solely from the reasoning behind the selection of treatments. If possible the questions posed should be equal in number to the degrees of freedom and should admit of separate study because no one can give a single answer to several diverse questions.

This paper shows how to define a contrast of interest and how to isolate it in the analysis of variance. Attention is given both to its contribution to the treatment sum of squares and to its variance (i.e. the precision with which it is estimated). Independence of estimation is also considered. Algebraic formulae are given for a restricted though important range of designs, which includes those that are completely randomized, in randomized blocks or in Latin squares, all treatments having the same replication. The methods can, however, be generalized to cover all designs. With these formulae it is possible both to test the existence of an interesting effect and to set confidence limits round its estimated value.

The resource conservation technologies (RCTs), being advocated for countering the threat to the sustainability of wheat–rice cropping system (RWCS) in the north–west (NW) Indo-Gangetic Plains (IGP) of India, have been evaluated mostly for the individual crops, without depicting the impact of these technologies on the succeeding or preceding crop. A study was thus conducted during 2012–2014 in NW India to assess the land and irrigation water productivity (WPI) of RWCS under different establishment and conservation tillage techniques in a sandy-loam soil (coarse loamy, calcareous, mixed, hyperthermic Typic Ustochrept). The treatments included zero (ZTW) and conventional (CTW) tillage in wheat as main plot, establishment methods (direct seeded (DSR) and mechanically transplanted rice (MTR)) as sub-plot and tillage in rice viz. puddle (PR), dry (CTR) and zero (ZTR) tillage as sub–sub plot treatments, replicated thrice in split–split plot design. The land productivity of RWCS was significantly lower in ZTW plots than in CTW plots. The residual effect of tillage in wheat on rice productivity was distinct during the second year of study, when the CTW plots recorded significantly higher (17.5%) rice yield than the ZTW plots. The productivity of the cropping system with DSR was statistically similar to that with MTR. The WPI of RWCS increased in the order ZTW–DSR–ZTR25 < CTW–DSR–ZTR < ZTW–MTR–CTR < ZTW–DSR–PR < CTW–DSR–PR < ZTW–MTR–PR26 < CTW–MTR–PR.

This study reports the results of model simulations of the potential yield of tea in north-east India. The CUPPA-Tea model, developed using data from a high-altitude site close to the equator in East Africa, was validated against the yield data from irrigation experiments conducted on contrasting soil types at Siliguri and Tezpur in the tea growing region of north-east India. The close correspondence between observed and predicted yield and yield distribution suggests that the model is applicable in north-east India. The model was used to simulate the yield response of tea to drought and irrigation using daily weather data for seven years (1983–89) at Siliguri and 14 years (1974–85) at Tezpur. On a clay loam soil at Siliguri, with an available water capacity of about 200 mm m−1, the predicted mean reduction in yield was 1.5 kg ha−1 for each 1 mm reduction in evapotranspiration. However, there appeared to be no reduction in evapotranspiration until the soil water deficit reached about 240 mm. By contrast, at Tezpur on loamy sand, with an available water capacity of about 100 mm m−1, evapotranspiration was reduced once soil water deficits exceeded about 85 mm. There was then a mean reduction in yield of 2.2 kg ha−1 for each 1 mm reduction in evapotranspiration. At both sites, even when soil water deficits were not limiting, the predicted year-to-year variation in yields was about 500 kg ha−1. The results highlight the soil-related differences in response to irrigation and the benefits of using process-based simulation models to investigate the potential yields over long periods.

Complete nutrient ± boron treatments were imposed on seedling and young oil palms growing in sand and water culture. A number of symptoms were observed on the boron-deficient palms, including the development of high endogenous auxin levels. The relation of morphological symptoms with IAA concentration is discussed. Comparisons were made of dry matter production, leaf area and leaf boron concentration.

Stands of pearl millet were grown in three controlled environment glasshouses in which were imposed different combinations of atmospheric saturation deficit (1.5 to 2.3 kPa) and soil water content (fully irrigated and not irrigated). Consistent differences in saturation deficit (SD) were maintained throughout the experiment (100 days) but a high water table restricted differences in water supply to the first 40 days. Responses to SD and soil water were observed in some variables but not in others. Developmental processes such as the rate of leaf appearance were unaffected, whereas the efficiency for conversion of intercepted solar energy decreased by 24% and the rate at which the canopy expanded by 50%, in the driest compared to the wettest conditions.

A survey of the system of rice intensification (SRI)-related literature indicates that different authors have drawn conflicting inferences about rice yield performances under the SRI, chiefly because the SRI methodology has been variously advocated, interpreted and implemented in the field using different rice varieties, seedling ages at transplantation, cultivation seasons and nutrient management regimes. In particular, the SRI method of single-seedling transplantation (SST) has potential economic advantage due to reduced seed costs, but it is not clear whether SST is an effective management strategy across a range of seedling ages, and whether there is any specific seedling age that is optimal for yield improvement of a given rice variety. This is an important consideration in rain-fed ecosystems where variable rainfall patterns and lack of controlled irrigation make it difficult to reliably transplant at a specific seedling age as recommended for the SRI. We conducted a five year-long experiment on a rain-fed organic farm using a short-duration upland and a medium-duration lowland landrace, following the SRI methodology. Rice seedlings of different ages (6, 10, 14, 18 and 28 days after establishment) were transplanted at 25 cm × 25 cm spacing in three replicated plots. The performance for each landrace was examined with respect to productive tillers, panicle density, total grain counts per hill and grain yield per unit area. Performances of seedlings of different ages were compared with that of control plots that employed all SRI practices with the exception that 28-day-old seedlings were transplanted with three seedlings per hill. The results indicate that (1) the SRI can improve mean panicle density if seedling age ≤ 18 days, but that responses differ between varieties; (2) the number of productive tillers per hill is significantly less in SST than that of multiple seedling transplants (MST) of 28-day-old seedlings of both upland and lowland varieties; (3) the total grain numbers per hill of the lowland variety is significantly greater for 14-day-old SST than 28-day-old MST; (4) the grain yield per unit area from young SRI transplants is significantly greater than that from 28-day-old MST for the lowland variety, although the magnitude of the improvement was small; (5) for the upland variety, grain yields declined with the oldest seedlings, but planting multiple seedlings per hill made the yield of the oldest transplants on par with that of younger seedlings planted singly. Our findings suggest that transplanting younger seedlings under the SRI management may not necessarily enhance grain yields.

Phosphorus (P) is one of the main limiting nutrients in the semi-arid regions where pearl millet is grown; its deficiency leads to poor seedling establishment and eventually poor crop yield. Experiments were carried out in pots and field-like conditions to evaluate the effect of seed priming and seed coating with P on the shoot biomass at two and four weeks after sowing (WAS), and on the panicle and stover yield at maturity of three hybrid varieties of pearl millet in low P Alfisol. Overall, seed priming did not increase shoot biomass at two and four WAS. In pots, seed coating at a rate of approximately 400 g P ha−1 increased vegetative biomass over 400% at early stages, and panicle yield by about 50%, over the non-coated treatment, with genotypic variation in the magnitude of the response. In field-like conditions, seed coating restored stover biomass to 85–100% of that in the non-limiting P treatment, whereas the panicle yield remained 25–35% lower than in the non-limiting P treatment, but still 45–65% higher than the non-coated treatment. P deficiency delayed the time to flowering by 20–24 days compared to the non-limiting P treatment, but plants in the seed coating treatment reduced that gap by 10–14 days. Seed P coating treatment appears a valid option to promote pearl millet seedling establishment and then to boost yield under low soil P conditions. The maintenance of an effect of seed coating on panicle yield in pots suggests a positive early effect on developmental processes before panicle initiation.

The arid zone of northwestern India is a unique adaptation zone for crop plants because of its pervasive severe moisture stress and high temperatures. Pearl millet (Pennisetum glaucum) is a major cereal in this zone as it represents approximately 25% of the total acreage of the crop in the country. Pearl millet hybrid cultivars, which have gained widespread acceptance from farmers elsewhere in the country, have not been adopted in the arid zone. Farmers continue to sow their traditional landraces because the yield advantage of current hybrids is not expressed in this zone, and the risk of failure in poor years with the hybrids is unacceptably high. The International Crops Research Institute for the Semi-Arid Tropics and the Indian Council of Agricultural Research have been collaborating to understand the unique nature of pearl millet in the arid zone since the late 1980s. This collaboration has produced a better understanding of how arid zone farmers manage their germplasm, of the unique features of this invaluable resource and of a range of ways of using this germplasm to produce well-adapted new varieties and hybrids that will meet the requirements of the farmers of the arid zone. It has been shown that new cultivars for the arid zone need to be based on parental materials, including traditional landraces that are specifically adapted to the arid zone. This paper summarizes the main lessons of nearly 20 years of this collaborative research.

The profitabilities of three land use systems in the humid zone of southwest Nigeria are compared using a capital budgeting procedure combining on-station and on-farm experimental data. The systems are: non-alley farming with fallow; alley farming with fallow; and continuous alley farming. The results indicate that: continuous alley cropping is more profitable than non-alley or alley cropping with fallow; short fallowing in alley cropping reduces the rate of mining soil fertility and thus helps preserve future productivity; alley farming with small ruminants enhances the profitability of alley systems and increases their advantage over the non-alley system; and alley systems remain profitable even when terminal clearing costs are internalized in the current project cycle.

Minimal competition was observed between adjacent plots of climbing bean varieties and maize in association, but there was a large head border effect which was not uniform among varieties. Head borders of 1 m at each end of the plot are recommended and a net plot size of 11 m2 with 3 replications for climbing bean varieties associated with maize was found to be adequate to detect significant differences in yield of beans of 24% of the mean. For climbing beans in monoculture a somewhat smaller plot (8 m2) would achieve the same level of precision. Larger plot sizes in general were needed for maize comparisons, especially in association.

In monsoon climates, the mean daytime saturation vapour pressure deficit (D), measured at screen height, decreases from a maximum of 3–4 kPa attained several months before rain arrives to a minimum of 0.5–1 kPa in the month of highest rainfall. Climatic records from India and West Africa were analysed to give the relation between D and precipitation (P mm month−1) as:

where n ranged from 0.5 to 0.9 between stations.

The dependence of dry matter production on D and therefore on P is evaluated when growth is restricted by rain and when this restriction is removed by irrigation. In the first case, the decrease in demand for water associated with a decrease in D is comparable in importance with the increase of water supply (P). The analysis has implications for the marginal response of crops to supplemental irrigation and for the interpretation of experiments with a line-source or rain-shelter.

The residual effects of three years' mulch application and the associated erosion processes, such as soil loss or deposition, on pearl millet (Pennisetum glaucum) growth have been investigated on a Sahelian sandy soil in field and pot studies. The smallest millet yields were found on unmulched eroded plots despite mineral phosphorus (P) applications, whereas stover mulching or manure and urine consistently resulted in larger yields. Bioassays revealed that aluminium (Al) by itself was not growth-limiting. Neither nematodes nor lack of micronutrients contributed to the small millet yields. On soil from eroded plots, millet dry matter yield tripled after P addition, and increased by a factor of 13.5 when additional nitrogen (N) was applied. High P availability was found to be the key to reversing decline in yields on erosion-affected fields, but the addition of organic material is a prerequisite to prevent acidification. Manure was more effective than straw because of the large amounts of N and P it contained. The addition of small quantities of lime (CaCO3) may partly compensate for organic matter addition by increasing soil pH and reducing P fixation. P-Bray was not a suitable indicator of plant available P on degraded sandy acid soils.