In a field experiment initiated in 1991 kharif season (April–October) on an acidic soil in the Western Himalayas of India, 25% and 50% of the recommended doses of nitrogen were substituted through different organics, viz. farmyard manure (FYM), wheat cut straw and Sesbania aculeata (as green manure) in rice, followed by use of chemical fertilizers in wheat each year. The aim of this work was to study the long-term integrated effect of organics and chemical fertilizers on grain yield of rice–wheat system and soil quality. Based on five years’ moving average values, continuous cropping without fertilization or manuring (control) gave the lowest grain yields of both rice and wheat. Application of 50% N through FYM plus 50% NPK through chemical fertilizers to rice followed by 100% NPK through chemical fertilizers to wheat (T3) maintained the highest productivity of rice and wheat at about 3.4 Mg ha−1 and 3.3 Mg ha−1, respectively, as found from the pooled grain yield over the years. The highest values of organic carbon, cation exchange capacity and available N, P, K were also recorded under this treatment (T3). Soil pH was marginally affected by different treatments, while Diphenyl Triamine Penta Acetic acid extractable micronutrient cations increased over control when chemical fertilizers were applied in conjunction with different organics.

The effect of ‘on-farm’ seed priming – soaking seeds in water before surface-drying and sowing them – was tested for mungbean (Vigna radiata) in 15 irrigated on-station trials and four sets of rainfed, paired-plot, farmer-participatory trials over four contrasting years from 1999 to 2002 in the North West Frontier Province of Pakistan. The optimum soaking time was found to be between six and eight hours; eight hours was used in all the trials. Of the 19 trials, priming was significantly better than non-priming in 14 with a mean yield increase of 56%. In the remaining five trials there was no difference between treatments but in no case was priming worse than not priming. In a subset of 11 on-station trials in which management was considered to be optimal, yield declined in a linear fashion as the date of sowing was delayed. The rate of decline of about 30 kg ha−1 d−1 after 1st June was similar for both non-primed and primed crops, although the latter declined from a higher base. Farmers' yields were proportional to rainfall over the four years and the mean increase in grain yield due to priming in the 39 trials was 30%. Benefits from priming were the result of a combination of faster germination and emergence and more vigorous growth and development, leading to better crop stands and bigger, more productive plants. It was concluded that ‘on-farm’ seed priming is a low-cost, low-risk technology that has the potential to raise mungbean yields substantially thus making it a more attractive crop for farmers.

Rates of leaf development in four groundnut genotypes were found to depend primarily on temperature, although there was a linear relation between the thermal time to produce one leaf and mean leaf water potential below −0.6 MPa. Flower, peg and pod production was analysed in relation to leaf number, since this integrated effects of temperature and water status.

When water was not limited, the ratio of pod number: peg number was about 0.8 for all four genotypes. During drought only one genotype (TMV 2) maintained this value, while for the other genotypes the ratio was approximately 0.15. Genotypes also showed different patterns of development during recovery from drought. TMV 2 maintained relatively high values of partitioning factor throughout the pod-filling period, resulting in the largest harvest index and pod yield. Kadiri 3 achieved the second largest harvest index and pod yield by maintaining production of pegs during drought and only forming pods when stress was relieved.

Farming systems research (FSR) has come to prominence as a part of tropical agricultural research in the past decade or so. The main stimulus was the growing realization that small farmers are ‘economically rational’ and agricultural economists have been the leading agents in developing FSR ideas. Three broad aspects are distinguished: (1) FSR sensu stricto, the deep analysis of farming systems as they exist, which is essentially an academic activity, (2) OFR/FSP (‘on farm research with farming systems perspective’), a practical adjunct to research which seeks to test the socio-economic suitability of research ideas on-farm before recommending extension and (3) NFSD (‘new farming systems development’) which seeks to develop complex, radical change rather than the stepwise change characteristic of OFR/FSP. The technical components of NFSD are probably mostly available but the necessary transdisciplinary, synthetic thinking is not. Research on perennial plants in tropical agriculture has been rather neglected but there are signs of growing concern; they must be an important feature of any NFSD for the wetter areas.

Reduced tillage is said to be one of the potential ways to reverse land degradation and ultimately increase the productivity of degrading soils of Africa. We hypothesised that crop yield following a modest application of 2 t ha−1 of crop residue in a reduced tillage system is similar to the yield obtained from a conventional tillage system, and that incorporation of legumes in a cropping system leads to greater economic benefits as opposed to a cropping system involving continuous maize. Three cropping systems (continuous maize monocropping, legume/maize intercropping and rotation) under different tillage and residue management systems were tested in sub-humid western Kenya over 10 seasons. While soybean performed equally well in both tillage systems throughout, maize yield was lower in reduced than conventional tillage during the first five seasons but no significant differences were observed after season 6. Likewise, with crop residue application, yields in conventional and reduced tillage systems are comparable after season 6. Nitrogen and phosphorus increased yield by up to 100% compared with control. Gross margins were not significantly different among the cropping systems being only 6 to 39% more in the legume–cereal systems relative to similar treatments in continuous cereal monocropping system. After 10 seasons of reduced tillage production, the economic benefits for our cropping systems are still not attractive for a switch from the conventional to reduced tillage.

The effects on yield of varying the planting date and planting pattern of morphologically different cowpea cultivars intercropped with pearl millet were studied in two field trials. The interaction between cowpea cultivars and planting date was highly significant. There was a sharp reduction in cowpea yields with late planting. Millet yields were reduced less when sown simultaneously with early cowpea cultivars than when sown with a late maturing local cultivar. Early maturing cowpea cultivars planted in closely spaced hills had less effect on millet yields than a late maturing cultivar sown in widely spaced hills. An appropriate cowpea cultivar for intercropping with peal millet would be one that was weakly competitive and that yielded both grain and fodder.

Growth and interception of Photosynthetically Active Radiation (PAR) in a maize/pigeonpea intercrop and sole maize and sole pigeonpea crops grown in large plots in an operational research watershed at ICRISAT research centre were compared. Growth and yield of the maize crop, in pure stands and in intercrop, were not significantly different. Efficiency of dry matter production, calculated from the relations between dry matter production and cumulative intercepted PAR, was highest for the maize/pigeonpea intercrop, followed by sole maize and sole pigeon-pea, proving the utility of such intercrops in making better use of resources in the Semi-Arid Tropics (SAT).

A review of the outcomes of past attempts at establishing sustainable seed producer groups in Nepal showed that after donor support was withdrawn a lack of marketing skills resulted in the groups no longer producing seed. Learning from this review, when we initiated new attempts at establishing sustainable seed producer groups in Chitwan district, Nepal, we emphasized the strengthening of their marketing and managerial capabilities rather than training in technical issues such as seed quality control. We imparted marketing skills to committee members of farmer groups at an initial training course in Chitwan in 2001. This inspired at least three existing farmer groups in Chitwan, already established for other agricultural activities, to enter into cereal and legume seed production and its marketing. Following their establishment in 2002 we supported them initially by purchasing some of their seed production. This was progressively withdrawn and, after three years, the groups independently marketed all of their substantial seed production. They built up capital reserves mainly from subsidies and by attracting funds from new shareholders with only a small contribution from retained profits that were only about 5% of total turnover. The capital reserves reduced or eliminated the need for loans thus increasing the chances that the enterprises would be sustainable. In contrast, other government-supported groups had practically no cash reserves despite substantial seed sales. By 2010, two of the three groups were still operating and had substantially increased turnover. Shareholders who were also seed producers benefited from being members of the group and from an increased income of 10% by producing seed instead of grain. Our intention in supporting these groups was to promote the scaling out of new rice varieties produced by client-oriented breeding (COB) or identified by participatory varietal selection but most of the seed that was produced was of obsolete varieties. Policies are needed to preferentially promote new varieties by supplying more information about them and increasing the subsidy on their seeds compared with older varieties. Continuing promotion by the organizations that bred them is also desirable but constrained by limited funding for COB.

In Ethiopia, irrigation is mainly implemented in small-scale irrigation schemes, which are often characterized by low water productivity. This study reports on the efficiency and productivity of a typical small-scale irrigation scheme in the highlands of the Blue Nile, Ethiopia. Canal water flows and the volume of irrigation water applied were measured at field level. Grain and crop residue biomass and grass biomass production along the canals were also measured. To triangulate the measurements, the irrigation farm management, effects of water logging around irrigation canals, farm water distribution mechanisms, effects of night irrigation and water losses due to soil cracking created by prolonged irrigation were closely observed. The average canal water loss from the main, the secondary and the field canals was 2.58, 1.59 and 0.39 l s−1 100 m−1, representing 4.5, 4.0 and 26% of the total water flow respectively. About 0.05% of the loss was attributed to grass production for livestock, while the rest was lost through evaporation and canal seepage. Grass production for livestock feed had a land productivity of 6190.5 kg ha−1 and a water productivity of 0.82 kg m−3. Land productivity for straw and grain was 2048 and 770 kg ha−1, respectively, for teff, and 1864 kg ha−1 and 758 kg ha−1, respectively, for wheat. Water productivities of the crops varied from 0.2 to 1.63 kg m−3. A significant volume of water was lost from small-scale irrigation systems mainly because farmers' water application did not match crop needs. The high price incurred by pumped irrigation positively affected water management by minimizing water losses and forced farmers to use deficit irrigation. Improving water productivity of small-scale irrigation requires integrated interventions including night storage mechanisms, optimal irrigation scheduling, empowerment of farmers to maintain canals and proper irrigation schedules.

Conservation agriculture (CA) was introduced to farmers in Malawi to address soil degradation, declining crop productivity and the need to adapt to climate variability and change. This research from 2005 to 2014 aimed at analysing the effects of CA on longer-term productivity and profitability compared with conventional systems as practiced in two communities of Central Malawi. CA treatments outyielded conventional ridge tilled control plots in Mwansambo and Zidyana on average by between 22 and 31%, respectively. An economic analysis from 2011 to 2014 found that, on average, income was 50 and 83% greater in CA systems than in conventional systems. The crops were produced with 28 -39 less labour days ha−1 compared with the conventional practice, leading to greater net benefits. Despite the higher returns with CA, there are still challenges with residue retention, weed control, adequate rotations, management of pests and diseases as well as other socio-economic constraints. At the same time, there are opportunities to address these challenges through site-specific and adaptive research using innovation systems approaches.

The Guinea savannas of Nigeria have a high potential for the production of maize because of favourable environmental conditions. Despite this high potential, the yields obtained in farmers' fields are still very low. This is due to soil degradation and nutrient depletion arising from intensification of land use. Nitrogen (N) is the major nutrient limiting maize production in the Guinea savannas where the use of inorganic fertilizers is low. One strategy for improving the productivity of maize is to select varieties that perform well under suboptimal soil N conditions. This study assessed the performance of diverse maize germplasm under a range of N levels. Growth and grain yields differed significantly between the genotypes at all N levels. These variations were more pronounced at zero and 30 kg N ha−1 than at 90 kg N ha−1. Grain yield under N-deficient conditions was correlated with an increased number of ears per plant, stay-green rating, leaf chlorophyll concentration, leaf area index, reduced anthesis–silking interval and reduced days to silking suggesting that these traits are linked to tolerance to N deficiency. One hybrid (Oba Super 2), the drought-tolerant genotypes and four maize genotypes previously selected for tolerance to N-deficient conditions performed better than the widely grown adapted controls under zero and 30 kg N ha−1. At zero N, the grain yield of maize decreased with advances in cycles of selection for tolerance to suboptimal N conditions suggesting that N deficiency in the selection environment was not sufficient to discriminate between genotypes. The good performance of drought-tolerant varieties under suboptimal N conditions suggests that selection for drought tolerance may confer tolerance to N-deficient conditions.

The effects of on-farm seed priming (i.e. seed soaking) on the emergence, growth and yield of cotton and maize were studied in the field in the south-eastern lowveld of Zimbabwe. Experiments were conducted on both crops in the 1999/2000 and 2000/2001 seasons and, in the 2001 winter season, on maize only. The interaction of priming with tillage (ox-drawn ploughing or hand-hoeing) and simulated sowing rainfall regimes (irrigations of 15 mm, 30 mm or 45 mm at planting) was studied. Priming usually increased the rate of emergence in maize, but always decreased final percent emergence in cotton. In the 2000/2001 season, there was an interaction between priming and simulated sowing rainfall regimes such that the 15 mm treatment gave a smaller adverse effect of priming in cotton than the 30 and 45 mm treatments. In maize, however, the 15 mm treatment gave an adverse rather than a positive effect of priming on emergence. There was little effect of tillage on emergence or growth. Priming did not affect the relative growth rate of cotton or maize, although plants grown from primed maize seed were consistently larger at any given date throughout the 2001 winter season. Plants from primed seed also flowered and matured earlier in the winter 2001 season. There were no significant effects of priming on yield, except in the 1999/2000 season, where priming decreased yield in cotton. It was concluded that the effect of priming can depend on crop species.

The present study documents critical analysis of drought-induced physiological responses in mulberry (Morus spp.) with insights into growth dynamics and leaf productivity. The study was performed for two years in a two-phase experimental design combining both field (experiment no. 1) and glasshouse (experiment no. 2) observations. In field assays, we surveyed 15 mulberry genotypes under two irrigation regimes: well-watered (20 to 24 irrigations in each growing season) and water-limited (irrigated once in a fortnight in each growing season). The genotypes were assessed for variation in key leaf gas exchange characteristics: net photosynthetic rates (Pn), stomatal conductance of CO2 (gs), transpiration rates (E) and instantaneous water use efficiency (WUEi). Leaf yield/plant was considered to determine the tolerance index (TI). Drought stress severely down-regulated leaf-level physiological variables in the susceptible genotypes resulting in poor leaf yield. However, genotypes S-13 and V-1 performed better in terms of leaf gas exchange and proved their superiority over other genotypes in drought tolerance. Conversely, genotypes DD and Bogurai were highly susceptible to drought. Under glasshouse conditions, the combined leaf gas exchange/chlorophyll a fluorescence measurements further dissected out stomatal and non-stomatal restrictions to Pn. As internal/ambient CO2 ratio (Ci/Ca) decreased concurrently with gs in non-irrigated stands, it appeared that greater stomatal limitation to Pn was associated with decreased photo-assimilation and leaf yield production. Further, higher leaf temperature (TL) (>35 °C) and down-regulation of maximum quantum yield of photosystem II (Fv/Fm) were apparent in the susceptible compared to the tolerant genotypes, which indicated chronic photoinhibition due to photo-inactivation of photosystem II centres in the susceptible genotypes. Drought-induced trade-offs in biomass allocation were also highlighted. Overall, our results suggest that greater rooting vigour and leaf hydration status, minimal stomatal inhibition and stabilized photochemistry might play major roles in maintaining higher Pn and associated gas exchange functions in drought-tolerant mulberry genotypes under water stress conditions. The higher leaf yield production in tolerant than susceptible genotypes can be attributed to minimal plasticity in foliar gas exchange traits and better quantitative growth characteristics under low water regimes.

The objective of this study was to calibrate and evaluate a simple crop yield model for 101 Brazilian soybean cultivars, and through the calibrated water deficit sensitivity index (Ky) to classify groups of cultivars in relation to drought tolerance. The cultivars’ actual yield was obtained from field experiments conducted by Pro-Seeds Foundation in 17 locations in southern Brazil from 2008 to 2011. Daily weather data were obtained from the government weather networks and rainfall was recorded at each experimental location. The crop yield model FAO–Agroecological zone was used to estimate potential yield (Yp), while the water deficit yield depletion model was used to estimate actual yield (Ya) and to determine Ky. Calibrated Ky values were used in a cluster analysis to determine groups of soybean cultivars with the same degree of drought tolerance. The crop yield model performed very well with lower values of mean absolute error (284 kg ha−1) and mean error (7 kg ha−1). The Ky values of 0.97, 0.90, 0.88 and 0.78 were obtained for the most sensitive soybean phenological phase to water deficit (flowering/yield formation), and were used to identify the groups of low, medium-low, medium-high and high drought tolerance respectively. In spite of Ky differences in cultivar groups, harvest index (CH) also varied, ranging from 0.31 to 0.35 for the group of high to low drought tolerance. The crop yield model proved to be an efficient tool for identifying drought tolerance of Brazilian soybean cultivars and for choosing the best cultivar for a given environment.

A defining characteristic of many rainfed tropical agricultural systems is their vulnerability to weather variability. There is now increased attention paid to climate-agriculture links as the world is focused on climate change. This has shown the need for increased understanding of current and future climate and the links to agricultural investment decisions, particularly farmers’ decisions, and that integrated strategies for coping with climate change need to start with managing current climate risk. Research, largely from an Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA) project to demonstrate the value of such increased understanding, is presented in this issue of the journal. Key lessons from this research are as follows:

1. 1. Statistical methods of analysis of historical climate data that are relevant to agriculture need not be complex. The most critical point is to describe the climate in terms of events of direct relevance to farming (such as the date of the start of a rainy season) rather than simple standard measures (such as annual total rainfall).

2. 2. Analysis requires access to relevant data, tools and expertise. Daily climate data, both current and historical, are primarily the responsibility of national meteorological services (NMS). Accessing such data, particularly daily data, is not always easy. Including staff from the NMS as research partners, not just data providers, can reduce this problem.

3. 3. Farmers’ perceptions of climate variation, risk and change are complex. They are keenly aware of variability, but there is evidence that they over-estimate risks of negative impacts and thereby fail to make use of good conditions when they occur. There is also evidence that multiple causes of changes are confounded, so farmers who observe decreasing crop production may not be distinguishing between rainfall change and declining soil fertility or other conditions. Hence any project working with farmers’ coping and adaptation to climate must also have access to analyses of observed climate data from nearby recording stations.

4. 4. Mechanisms for reducing and coping with risks are exemplified in pastoral systems that exist in the most variable environments. New approaches to risk transfer, such as index-based insurance, show potential for positive impact.

5. 5. Skilful seasonal forecasts, which give a better indication of the coming season than a simple average, would help farmers take decisions for the coming cropping season. Increasing meteorological knowledge shows that such forecasting is possible for parts of Africa. There are institutional barriers to farmers accessing and using the forecast information. Furthermore, the skill of the forecasts is currently limited so that there are maybe still only a few rational choices for a farmer to make on the basis of a forecast.

With the justified current interest in climate and agriculture, all stakeholders including researchers, data providers, policy developers and extension workers will need to work together to ensure that interventions are based on a correct interpretation of a valid analysis of relevant data.

The agricultural research and development institutions in most developing countries are poorly equipped to support the needs of millions of smallholder farmers that depend upon them. The research approaches taken by these systems explicitly or implicitly seek simple, one-size-fits-all solutions for problems and opportunities that are extremely diverse. Radical change is needed to facilitate the agroecological intensification of smallholder farming. We propose that large-scale participatory approaches, combined with innovations in information and communications technology (ICT), could enable the effective matching of diverse options to the wide spectrum of socio-ecological context that characterize smallholder agriculture. We consider the requirements, precedents and issues that might be involved in the development of farmer research networks (FRNs). Substantial institutional innovation will be needed to support FRNs, with shifts in roles and relationships amongst researchers, extension providers and farmers. Where farmers’ organizations have social capital and strong facilitation skills, such alignments may be most feasible. Novel information management capabilities will be required to introduce options and principles, enable characterization of contexts, manage data related to option-by-context interactions and enable farmers to visualize their findings in useful and intelligible ways. FRNs could lead to vastly greater capacity for technical innovation, which could in turn enable greater productivity and resilience, and enhance the quality of rural life.

Plants of yam, taro, tannia, cassava and sweet potato were raised under shade or in full sunlight and the effect of shade on leaf chlorophyll and carotenoids was examined to determine and compare the relative shade tolerance and adaptability of the var ious species. All five species of root crops adapted to shade. The chlorophyll concentration was higher, while the chlorophyll a:b ratio, carotenoids per unit chlorophyll and the weight per unit area of leaf were lower in the shade than in the su n in yam, tannia, taro, cassava and sweet potato. All species had larger leaves and more chlorophyll per leaf in the shade. The extent of the changes, however, differed between species. The aroids (taro and tannia) appeared to be shade-tolerant species as their chlorophyll a:b ratios changed less than those of the other species in the shade, suggesting that their light-harvesting systems may be normally adapted to shade conditions. Taro and tannia also adapted to shade by a greater proportional i ncrease in leaf size, a smaller reduction in leaf weight per unit area and a greater proportional increase in chlorophyll and carotenoids per leaf than the other species. Yam compensated for shade by having a large proportional increase in leaf size and a ppeared to be moderately tolerant of shade. Sweet potato and cassava appeared to be the least tolerant of shade of the major tropical root crops.

Pearl millet (Pennisetum typhoides) was grown on stored water at Niamey, Niger, using three row spacings (38, 75 and 150 cm), to determine the physiological basis of exploitation and conservation of water by crops during drought Between 18 and 32 days after sowing, roots grew rapidly beneath all crops reaching 140 cm in the narrow spacing, but there were differences between crops in the pattern of growth. Soil cores and trench profiles indicated that plants in wider rows had fewer, deeper roots. Substantial differences in both the amount and pattern of shoot growth were recorded in the different populations. Initially growth was fastest at the narrow spacing but stopped by day 45 and eventually the wide spacing produced most dry matter due mainly to greater survival of tillers. The partitioning of above ground dry matter into vegetative and reproductive fractions was similar at all three spacings and was consistent with figures for comparable crops elsewhere. The important role of tillers is discussed in relation to the development and maintenance of a canopy.

Performance of Short Kaura, a photosensitive Nigerian sorghum, was compared at Samaru in ten sowings in 1972. Except for a two-week interval between the fifth and sixth sowings, all sowings were at weekly intervals from 12 May to 21 July. Total dry weight and grain yield decreased with delay in sowing after 26 May at the rate of 1700 kg.ha.−1 week−1 and 360 kg. ha.−1 week−1 respectively. Each week's delay in sowing after 12 May shortened the total growth cycle by 5·9 to 6·0 days, with 77 to 78 per cent in the vegetative phase, 7 to 8 per cent in the head development phase and 14 to 16 per cent in the grain filling phase. Although the date of head initiation seemed to be determined by photoperiod, sowing date also had a small but definite effect.

In a field experiment, the effects of irrigating crops alternately with sodic water (high in sodium adsorption ratio and ) and good quality canal water were investigated for six years on a well drained sandy loam (Typic Ustochrept). The irrigation treatments included: irrigation with non-sodic canal water (CW), irrigation with sodic water (SW), CW irrigation alternating with one or two SW irrigations, and two CW irrigations alternating with one SW irrigation. The results showed that the use of sodic water increased the sodium saturation of the soil and decreased rice and wheat yields. The build-up of sodium depended on the number of SW irrigations during the season. The increase in sodium saturation and decline in crop yields were progressive over the years. The improvements in yield due to alternating sodic and non-sodic irrigations compared with the use of sodic water alone increased over the years. Alternating sodic and non-sodic irrigations could therefore be considered a practical way to alleviate the problems caused by sodic water. The number of sodic irrigations during a season should, however, be kept to a minimum and the build-up of sodium in the soil over time should be monitored.