The effects of four calcium-containing materials on soil pH, nutrient availability and productivity of groundnut (Arachis hypogaea) on acid soils were studied in field experiments conducted at the Horticulture Research Centre and the Makoholi Experiment Station in Zimbabwe. The materials were calcitic limestone, dolomitic limestone, gypsum and single super phosphate.

Application of dolomitic or calcitic limestone significantly increased soil pH and exchangeable calcium and magnesium levels, whereas gypsum and single super phosphate did not. Application of 4000 kg ha−1 calcitic limestone increased calcium levels by up to 125% at the Horticulture Research Centre and 872% at Makoholi Experiment Station, while dolomitic limestone increased magnesium levels by 183% and 473% at the Horticulture Research Centre and Makoholi Experiment Station respectively. Combining gypsum and single super phosphate with 2000 kg ha−1 calcitic or dolomitic limestone did not affect soil pH differently than the limes alone. Furthermore, gypsum and single super phosphate applications on their own had no effect on pH, calcium and magnesium levels. The phosphorus, potassium and nitrogen levels were not significantly affected by the calcium-containing materials.

Application of either dolomitic or calcitic limestone significantly improved productivity of groundnut, with 4000 kg ha−1 calcitic limestone producing the largest increases in kernel yields at both sites. Yield responses to gypsum were not significantly different from the control treatment. Despite the notable changes in soil chemical properties observed at both sites, deficiencies of nitrogen, phosphorus, potassium, calcium and magnesium, coupled with low pH per se, remained the primary reasons for poor growth on the acid sandy soils at both sites.

Changes in plant dry weight and nitrogen content of Trifolium semipilosum cv. Safari and T. repens cv. Grasslands Huia were monitored when the root systems of effectively nodulated 28-day-old plants were exposed to a range of constant and diurnal temperatures for 21 days. Nitrogen fixation was more sensitive to high root temperatures than was dry weight accumulation, and T. semipilosum was relatively more tolerant of high root temperatures than T. repens for both dry weight and nitrogen content. The optimum temperatures for dry weight yield and nitrogen fixation (≡nitrogen content) were similar (21–23°C) for both species.

Our data suggest that growth and nitrogen fixation in T. semipilosum are more tolerant of short-term exposure to increase in root temperature than in T. repens. In addition, both species accumulated more dry matter and fixed more nitrogen when night temperatures were reduced from either 30 or 35°C to 25°C. The increase was greater with T. semipilosum and may be a major factor in its adaptation to the humid subtropics and cooler (elevated) tropics.

The effects of component population, rhizobial inoculation and applied nitrogen on the efficiency of phosphorus utilization in maize/mungbean intercropping were examined in two experiments. The efficiency of phosphorus absorption decreased by between 5 and 43% in maize and by between 31 and 58% in mungbean as a result of intercropping. The overall efficiency of phosphorus absorption in intercropping decreased with increasing nitrogen level but a parallel increase in overall conversion efficiency maintained a constant and large land equivalent ratio (LER) up to the highest level of nitrogen. The increase in LER over unity, however, was due primarily to the greater total absorption of phosphorus by maize and mungbean together in intercropping compared with that when they were grown in pure stands.

We evaluated the effects of cattle manure and inoculation with arbuscular mycorrhizal fungi (AMF) in maize plants growing in a semiarid area of Brazilian north-east in 2012 and 2013. Three isolates of AMF (Acaulosporalongula URM-FMA 07 and URM-FMA 03, Claroideoglomusetunicatum UNIVASF 06A) were used, with or without the application of cattle manure, during two growing cycles. In the first year, significant effects of inoculation were detected for straw yield only when the manure was applied. In the second year, there was an interaction between fertilisation and inoculation for plant height and grain yield, with the highest values in the fertilised treatments. Inoculation with A. longula demonstrated that mycorrhizal inoculation in field-grown plants could be an alternative management for improving plant growth and grain yield, reducing the use of cattle manure. The AMF sporulation and mycorrhizal colonisation were improved after inoculation, and A. longula URM-FMA 07 increased sporulation by more than 15 times while inoculation with C. etunicatum increased sporulation by more than 3 times. The mycorrhizal inoculation is a management practice that can be useful for recovering or maintaining AMF infective propagules in soil, showing potential to be used in large-scale field conditions in Brazilian semiarid. Although mycorrhisation presents high agricultural relevance due to benefits promoted to the soil and plants, the knowledge about the factors influencing the interactions among microorganisms, soil and plants need to be broadened aiming to achieve successful crop management in semiarid regions.

When the agricultural value chain involves profit making, it results in changes in the production and distribution relationships among men and women in terms of access to and control of markets, resources and benefits emanating from product value chain participation. This affects not only individual incomes but also gender equality. This study examined gender relationships in the cassava value chain in the Kigoma region of Tanzania. The aim was to assess gender participation in the cassava value chain. Multi-stage sampling was used to select the respondents in four districts. A structured questionnaire was administered to 384 randomly selected household heads. A chi-square test was used to test for significant relationships among the variables. Results indicated that gender was significantly related to socio-economic characteristics. About 34% of the women participating in the cassava value chain were young, some below 17 years of age. There were significant relationships between gender and access to resources (land, extension services and markets), control over resources (land, house and household assets) and benefits (revenue) generated from cassava value chains. Overall, there was gender disparity in participation along the cassava value chain. These results suggest that any intervention in the cassava value chain should consider gender relations to benefit men and women and alleviate household poverty.

Field experiments were carried out during the rainy seasons of 1985 and 1986 to examine the frequency of weeding necessary for the optimum growth and yield of okra in Nigeria. Weed removal within 12 weeks of sowing generally resulted in significantly better crop growth and yield than that in the weedy check. Weeding once as early as four weeks was as beneficial to okra growth and yield as two or three weedings later in the 12 week period. Weed removal four times at 3, 6, 9 and 12 weeks significantly enhanced crop growth and pod yield over all other treatments. For good pod yields, protection from weed competition over most of the duration of crop growth is therefore essential. Such weed removal may enhance crop yield partly by increasing aeration and water movement in the soil.

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.

This paper reports results of a study to investigate the problem of introducing an improved technological package into the farming system in one area of northern Nigeria. It examines the economic and technical feasibility, as well as the social acceptability to the farmer, of growing sole cowpea given his environment and constraints. Studies of this nature are important as they provide insight into the problems farmers experience with improved technologies and thus represent one way of determining how to narrow the gap between yields farmers obtain and those obtainable at the research station level.

Seasonal fertilizer response of napier grass (Pennisetum purpureum) was measured on various soils in Brunei. Climate was moderately humid over the three-year experimental period, with the longest dry spell about 4 months. Optimal fertilizer N levels (balanced with other nutrients) ranged from about 240 to 900 kg/ha/yr on the different soil types and under different moisture conditions. Dry forage yields at the optimum fertilizer levels ranged from 5 t/ha/yr on sandy soil under dry conditions, to 55 t/ha/yr on a sandy clay loam with adequate water. Moderate production of about 20 t/ha/yr was obtained on acid sulphate soil with fertilizer and lime. Digestible nutrient and protein levels of 60-day forage were about 55 and 10% respectively.

Intercropping Brussels sprouts with cabbage was studied in two experiments comparing four different intercropping systems with sole crop production. Intercropping presented no agronomic or management problems because both crops had compatible cultural and crop protection requirements. Analysis of Land Equivalent Ratios and Relative Value Totals showed that the four intercropping systems gave consistently larger yields than the sole crops. In one experiment profitability, measured by the gross margin, was higher from all of the intercropping systems and costs per unit of produce were reduced. Similar results were obtained with one intercropping system in the other experiment. Alternative methods of evaluating the results in economic terms are discussed, together with the implications of intercropping in high-input systems of vegetable production.

Trials were made of the performance of batches of forage sorghum and maize, sown at different times of year. The optimum sowing periods of sorghum variety Abu Sabeen and maize variety 113 were found to be February to October and November to January respectively. Of the various climatic factors considered in this study, mean daily temperature was of greatest importance in affecting yield. The overall performance of sorghum was superior to that of maize, probably because of its relatively higher salt tolerance.

As a result of higher prices and improved marketing, cashew (Anacardium occidentale) farmers in Tanzania are trying to improve production through improved husbandry. The main production constraint is powdery mildew disease which causes large reductions in tree yields. Although fungicides can control this disease, the majority of farmers are unable to afford them. Recently, cashew material with some tolerance to the disease has been released to growers and use of this material will be one of the main ways for farmers to cope with the disease. Cashew is grown principally by smallholders in Tanzania and since 1993 ways for farmers to increase production by including improved material on their farms have been investigated in participatory trials. The most important initial step is to fell non-productive trees. Where there is sufficient space these can be replaced by improved material established either as grafted plants, polyclonal seed or by top-working. Improved material can also be planted in gaps amongst the trees.

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.

Agronomic techniques to even out the intra-seasonal fluctuations in yields of tea in Malawi are described, and evidence presented of their effects on the level and distribution of yield. Such treatments reduce yields per acre, but by overcoming constraints on capacity they may lead to increased yields for the estate as a whole. The full benefit of some of these practices requires the prediction of yield patterns based on current and expected weather. Several techniques can be combined to form a flexible approach adapted to each particular year, but more work is required to quantify the parameters and functional relations involved before alternative strategies can be properly compared.

In spite of large year-to-year variations in clove yields, production in the islands of Zanzibar and Pemba is often in synchrony and the annual harvests of the two islands are correlated with similar variables. Clove harvests are positively correlated with rainfall in October to February two years before the harvest and negatively correlated with the harvest in the previous year and rainfall around July, and October to December of the year before the harvest. It is likely that rainfall in these periods affects vegetative growth of the clove tree and clove bud differentiation.

A common practice in some South American countries consists in moving around Capsicum chinense cultivars between regions where edaphoclimatic conditions differ notably. The purpose of this research was to compare and relate gas exchange responses with assimilate allocation patterns and flower and fruit production dynamics in a cultivar of C. chinense in three locations with different mean temperatures (19, 24 and 28 °C) along a gradient from 140–1855 m. Leaf gas exchange (leaf conductance, CO2 assimilation and transpiration rates) was measured at 60–70, 110–120 and 140–150 days after transplanting (dat) from seed beds. Dry weight per plant of leaves, stems and roots were determined at 50, 73, 96, 114 and 196 dat. Flowering dynamics and fruit production were followed weekly. A marked reduction (50%) in mean Gs was found at the site with the lowest mean temperature in relation to plants grown at the highest temperature site. Mean daily CO2 assimilation rate was higher for plants in the intermediate site and a reduction of 18 and 42% was found for sites with highest and lowest mean temperature, respectively. We report an adverse effect of low temperatures on growth of C. chinense. Flowering initiation and fruit production was delayed at lower temperatures. An increase in temperature (between 26–30 °C) led to an increase in the number of flowers; below this temperature it remained unchanged. Fruit production is drastically reduced at the lower temperature site due to a large number of aborted flowers and small fruits.

There is no one widely accepted method of managing international agricultural research and numerous different models exist. Here we review one in particular, referred to as the ‘institute without walls’, from the perspective of the UK Department for International Development's (DFID) Renewable Natural Resource (RNR) Research Strategy (1990–2006). We begin with a brief history of the RNR Research Strategy from 1990 to 2004. We then draw on nearly 15 years experience of managing one of the programmes within the RNR Research Strategy to assess critically the impact of externally and internally imposed organizational and management changes on the performance of the DFID Plant Sciences Programme (PSP). The current RNR Research Strategy (1995–2006), with its emphasis on demand-led research, has greatly increased the relevance and effectiveness of DFID's natural resources research. A comparison between the PSP in 2004 and the early 1990s inevitably concludes that the programme has been transformed: unlike in 1991, research is now firmly demand-driven, much is based in developing countries and farmers are benefiting from the research. Over time, the outputs of the long-term strategic research have been applied in practical plant breeding and participatory crop improvement programmes. Key to the success of the PSP has been the provision of continuous, long-term funding which has allowed projects time to develop and produce outputs of real value to end users. Alongside this, the ability of the PSP to build long-term, in-country partnerships has ensured the effective adoption of its research outputs. We conclude that the successes of the PSP have largely derived from (i) identification of research that is clearly demand driven, (ii) continuous long-term funding that has allowed research to move from the strategic to adaptive phase, (iii) continuity of management, and (iv) the flexibility to develop a wide range of partnerships, both in-country and overseas, based on their ability to deliver.

Native plantlets of Allium cepa (onion) were cultivated in selenium (Se)-supplemented soils to observe dose- and time-dependent uptake and associated pro/anti-oxidant activity. Allium plantlets were grown in soils supplemented with Se at 2.5, 5.0 and 7.5 mg kg−1 as selenite (Na2SeO3) and selenate (Na2SeO4) for 40–120 days. The effect of different concentrations of Se oxyanions on the growth and accumulation profile in plants in relation to glutathione peroxidase activity and thiobarbituric acid reactive substances was studied. Total Se concentrations in plantlets were determined by instrumental neutron activation analysis. The accumulation of Se in plant was observed to be dose dependent in the case of selenite, but, no definite correlation between accumulation levels and exposed concentration was observed. The changes in pro/anti-oxidant properties were observed to be dependent on the accumulation of Se in plant.

Supplementary irrigation experiments were conducted on a Clansthal sand and a Windermere clay. Irrigation treatments were based on the application of 1 inch of water when the soil moisture deficit reached 2·5, 3·5, 4·5 and 5·5 in. in 7 ft of soil on the sand, and 1·00, 1·75, 2·50 and 3·25 in. in 2 ft of soil on the clay. Each experiment included a dryland control and soil moisture was estimated weekly in each plot with a neutron probe. The results showed that there were significant linear increases in yield with increasing quantities of water applied. The crops exploited soil moisture to a depth of 6 ft in the sand and 3 ft in the clay, even with the maximum water treatments. Under dryland conditions, on the sand the crop exploited soil moisture to the wilting point only in the surface foot of soil, but on the clay the crop extracted moisture held at tensions greater than 15 bars in the top 3 ft of soil. The conclusions are that, where available water for supplementary irrigation is limited, heavy soils should be irrigated in preference to sandy soils, and that the most efficient use of both rainfall and irrigation water is achieved when 1 cusec is used to irrigate about 200 acres.