There were significant differences in dry matter yield among five forage oat varieties tested at ten environments during 1970–75. The correlation coefficients between annual rainfall and DM yield varied with variety from 0·69 to 0·88, late varieties tending to give higher yields. Lateness, and high varietal response to annual rainfall and improved environmental conditions, can be used as selection criteria in semi-arid regions. Late varieties had higher DM and lower crude protein contents, and forage produced under lower rainfall conditions tended to have more DM and crude protein.

Crop bioengineering provides unique and dramatic opportunities for international agricultural development. However, we consider the technology not as a ‘silver bullet’ or panacea for crop improvement in the developing world but as an increasingly important tool that can be used to complement conventional methods of crop improvement. The number of bioengineered crops ready for commercial release in developing countries is expected to expand considerably in the next few years. But the multi-national life sciences companies that are leading the research, development and commercialization of bioengineered crops focus primarily on major crops that have high commercial value and extensive international markets. These companies also hold proprietary gene technology for many other crops of extreme importance to subsistence and resource-poor farmers but do not pursue product development and commercialization because of low anticipated returns. Such crops have traditionally been overlooked and are sometimes referred to as ‘orphan crops’ because of the relative lack of research and development applied to them. We propose a strategy for the development and delivery of bioengineered crops, including orphan crops, for developing countries. Consulting local public and private sector stakeholders to determine their highest priority needs for agricultural products is the first step. This ensures local stakeholder buy-in and that we do not invest in technology that is unlikely to be adopted. Next, the feasibility of developing and delivering the product is assessed. If the result is positive, the work is organized into ‘product commercialization packages’ (PCPs) that integrate all elements of the research, development and commercialization processes. The main elements of each PCP include (i) technology development; (ii) policy-related issues such as intellectual property and licensing, as well as gaining regulatory approval by the relevant national authorities; (iii) providing public information to producers and consumers about the benefits, risks and correct management of these new products; and (iv) establishing, or verifying, the existence of marketing and distribution mechanisms to provide farmers access to planting material. Our strategy involves integration of needs-based capacity building, socio-economic impact studies and product stewardship into each PCP. Whenever appropriate, opportunities are sought to create public–private partnerships to help leverage public funds, help absorb development costs and provide a broader distribution channel. To illustrate how our strategy is being translated into action we include, as a case study, examples of work by the US Agency for International Development-funded, Cornell University-led Agricultural Biotechnology Support Project II on the research, development and delivery of bioengineered fruit and shoot-borer-resistant eggplant varieties (Solanum melanogena) for South and Southeast Asia.

The area of dry-season rice (Oryza sativa L.) has rapidly increased in Cambodia owing to the large-scale development of irrigation infrastructure. But little is known of potential productivity and adaptive crop management. The objective of our study was to evaluate potential yield and nutrient requirements of dry-season rice in Cambodia, and the economic feasibility of soil-specific management recommended by the government. Field experiments were conducted on four soil types (Bakan, equivalent to Alfisol; Krakor, Inceptisol; Prateah Lang, Plinthustalfs; and Toul Samroung, Endoaqualfs) in four provinces (Battambang, Kampong Thom, Pursat, and Siem Reap) during the 2016 and 2017 dry seasons to compare 14 (2016) and 8 (2017) N-P-K combinations. Grain yield ranged from 1.0 to 5.5 t ha−1 in 2016 and from 1.3 to 6.7 t ha−1 in 2017. Potential yield from the experiments was 6–7 t ha−1 on Toul Samroung soil, 5–6 t ha−1 on Bakan soil, and 3–5 t ha−1 on Prateah Lang and Krakor soils. A rate of 140-60-60 kg ha−1 of N-P2O5-K2O was more than enough to achieve the best yields on any soil group. On the other hand, modest application rates in soil-specific management (44–78 kg ha−1 of N, 23–28 kg ha−1 of P2O5, 0–30 kg ha−1 of K2O) proved reasonable for resource-poor farmers in Cambodia, since the treatment always provided >75 % of the highest economic profit in high-input plots.

Soil and nutrients losses due to soil erosion are detrimental to crop production, especially in the hilly terrains. An experiment was carried out in three consecutive cropping seasons (2012–2015) with four treatments: sole maize; sole maize with plastic mulch; maize and cowpea under plastic mulching; and maize and soybean under plastic mulching in randomized block design (RBD) to assess their impact on productivity, profitability, and resource (rainwater, soil, and NPK nutrients) conservation in the Indian sub-Himalayan region. The plot size was 9 × 8.1 m with 2% slope, and runoff and soil loss were measured using a multi-slot devisor. The results showed that mean runoff decreased from 356 mm in sole maize with plastic mulch plots to 229 mm in maize + cowpea intercropping with plastic mulch, representing a reduction of 36% and corresponding soil loss reduction was 41% (from 9.4 to 5.5 t ha−1). The eroded soil exported a considerable amount of nitrogen (N) (13.2–31.4 kg ha−1), phosphorous (P) (0.5–1.7 kg ha−1), and potassium (K) (9.9–15.6 kg ha−1) and was consistently lower in maize + cowpea intercropping. The maize equivalent yield (MEY) was significantly higher in maize + cowpea with plastic mulch intercropping than the other treatments. These results justify the need to adopt maize with alternate legume intercrops and plastic mulch. This strategy must be done in a way guaranteeing high yield stability to the smallholder farmers of the Indian sub-Himalayan region.

The use of chemical fertilizers is among the main innovations brought by the 1960s Green Revolution. In Ethiopia, fertilizer application during the last four decades has led to significant yield gains, yet yield remains below its potential across much of the country. One of the main challenges responsible for low yield response to fertilizer application has been the use of ‘blanket’ recommendations, whereby no tailoring of fertilizer amount and frequency is done based on soil requirements. As a result, the amount of fertilizer applied ranges widely, and can be either sub- or supra-optimal. There is thus an increasing need for site-specific fertilizer recommendations which take into account site characteristics such as climate variables (temperature, rainfall, and solar radiation); soil factors (soil organic carbon, moisture, pH, texture, cation exchange capacity, and level of macro- and micronutrients); and topographic position indices. This article reports on a data-mining approach we developed on a large dataset of 6585 wheat (Triticum aestivum) field trials. The dataset includes detailed, site-specific biophysical variables to create nutrient response functions that can guide optimal site-specific fertilizer application. The approach used a machine-learning model (random forest) to capture the relationship between nutrients – nitrogen (N), phosphorous (P), potassium (K), and sulfur (S) – and wheat yield. The model explained about 83, 82, 47, and 69% of variances of yield for N, P, K, and S omission, respectively, with consistent performance across training and testing datasets. Expectedly, for N and P omission data, the most important explanatory variables are nutrient rate, followed by soil organic carbon and soil pH. For K and S, however, climatic variables played an important role alongside nutrient rates. The site-specific yield–fertilizer response curves derived from our model are highly variable from location to location, as they are affected by the climatic, soil, or topographic conditions of the site. Importantly, using principal component analysis, we showed that the shape of the fertilizer response curves is a result of the multiple environmental factors (including soil, topography, and climate) that are at play at a given site, rather than of a specific dominant one. The research output is expected to respond to the national policy demands for a sound method to identify the optimal fertilizer rate to increase economic returns of fertilizer investments and take fertilizer utilization research one step further.

Low and unreliable rainfall, combined with high summer evaporation rates, frequently lead to poor yields and crop failure in Botswana agriculture. Over three test years it has been shown that the soil can store up to 100 mm. of available moisture at planting time, which represents about half the water requirement of a crop of sorghum, and the balance is likely to be met (P = 0.05) during the current growing season. Sorghum grain yields have been doubled (2007 kg./ha.) after fallow compared with 1028 kg./ha. after non-fallowed pre-treatments. The advantages of a farming system based on a bare summer fallow are discussed, and reference is made to the implications of its wider adoption.

Root-knot nematodes represent a serious threat to world coffee production, especially Meloidogyne incognita and M. paranaensis. Most cultivars of Coffea arabica are highly susceptible to these parasites and cultivation in infested areas has only been possible with the use of resistant C. canephora rootstocks. In this research, three elite clones of C. canephora, selected in areas infested by M. incognita and M. paranaensis, were evaluated in controlled conditions to assess levels of resistance against two populations of M. paranaensis, four populations of M. incognita and a mixed population of both species. The three clones were resistant to both species, but CcK1 and CcR2 were considered most promising because their vegetative growth was not impaired by nematodes.

Over 90 % of the farmers around Marsabit Mountain, a pocket of arable land amidst a predominantly arid area in northern Kenya, are former pastoralists, unfamiliar with productive and sustainable farming technologies. This paper describes how encouraging farmer innovativeness enhanced adoption and adaptation of water-saving technologies to suit individual farmers' needs. When farmers understood the principles behind a technology they were more likely to adapt it. Both men and women farmers were most interested in increasing their available income through improved technologies, but more women than men ranked labour saving as an important attribute of a new technology. More women adopted the new technologies, but men used them on a larger area than women. The paper also shows that agricultural productivity can substantially increase even if the theoretical full potential of the recommended practices might not be achieved. It is concluded that farmers need to be exposed to new ideas in exciting and thought provoking ways to tap their innovation potential.

The results are reported of an experiment on the Lilongwe Plain to investigate the effects of under-sowing maize with a mixture of Rhodes grass and silverleaf desmodium. Undersowing caused no significant reduction in any component of maize yield, and mixed swards with a good legume content were established. Nitrogen application had no significant effect on yields of grain or pasture, but in the following year undersown swards outyielded those directly seeded. Some practical advantages of undersowing are discussed.

The nitrogen content of weeds was significantly higher than that of Dular rice-straw, but with Taichung Native I rice in winter there was no significant difference between the nitrogen in weed samples and rice plants at the tillering stage. Rice straw contained a higher proportion of nitrogen where there were three hand weedings. The total dry matter of rice was much reduced by weed competition. Weed species contained much nitrogen at the vegetative, flowering and post-flowering stages, indicating severe competition for nitrogen by weeds throughout the growth of rice under dry land conditions.

Comparison of an overhead boom sprayer (Monica Mist) with a conventional air-assisted sprayer (Conomist) showed that the former gave relatively poor cover, but control of coffee berry disease (CBD) was equally good with both machines. It is suggested that the success of overhead spraying is dependent upon effective redistribution of fungicide within the tree canopy during rain.

The International Benchmark Sites Network for Agrotechnology Transfer (IBSNAT) project has established an international network of co-operating farming systems researchers. A decision support system that includes a number of crop models and databases has been developed to assist in the evaluation of new agrotechnology packages in the tropics and sub-tropics. Standards have been established for the recording of ‘minumum data sets’ from field experiments to allow the crop models to be validated for specific sites. The decision support system, still under active development, has the potential to reduce substantially the time and cost of field experimentation necessary for adequate evaluation of new cultivars and new crop management systems.

Correct placement of side dress nitrogen (N) fertilizer could increase nitrogen use efficiency (NUE) and maize yield production. Field studies were established to evaluate application of midseason (V8 to V10), variable liquid urea ammonia nitrate (28%), N rates (0, 45, 90 and 134 kg N ha−1) and different application distances (0, 10, 20 and 30 cm) away from the maize row on grain yield and NUE at Haskell and Hennessey in 2009, Efaw in 2010 and Lake Carl Blackwell, Oklahoma in 2009 and 2010. A randomized complete block design with three replications was used throughout the study. Results indicated that maize grain yield in sites with adequate rainfall increased significantly (p < 0.05) with N rate, and poor N response was recorded in sites with low rainfall. Across sites and seasons, varying side dress N application distance away from the maize row did not significantly (p < 0.05) influence maize grain yield and NUE even with no prep-plant applied. Environments with adequate rainfall distribution had better maize grain yields when high side dress N rates (90 and 134 kg N ha−1) were applied 0 to 10 cm, and a higher NUE when 45 kg N ha−1 was applied 0 to 20 cm away from the maize row. For low N rates (45 kg N ha−1), increased maize grain yield and NUE were achieved when side dress N was applied 0 to 20 cm away from the maize row at locations with low rainfall distribution. Across sites and seasons, increasing side dress N to 134 kg N ha−1 contributed to a general decline in mean NUE to as low as 4%, 35%, 10%, 51% at Hennessey, Efaw, LCB (2009) and LCB (2010) respectively.

Data from uniformity trials on healthy and diseased wheat and oat crops showed that the coefficient of variation for yield decreased as plot size increased and became nearer to square in shape. Infection with Septoria leaf blotch of oats and powdery mildew of wheat did not appear to affect yield variability. Plots larger than rod row size (where 16 ft of the centre row of 3 rows is harvested) are recommended to detect differences of 10 per cent in yield between two treatments.

In trials of seedling cocoa in Ghana, biases in the estimates of yield and tree size arising on the perimeters of experiments and on the interfaces of unguarded plots were strongly correlated, characteristic of progenies and stable across environments, but were inconsistent for black pod losses. No variate showed progeny × site interactions, but those of Caribbean yield data were interpreted by principal components analysis. The results show that 25-tree plots may be used for initial tests of new varieties and, as long as the environmental variation does not exceed that of the Ghanaian trials, at single sites.

Landowners can engage in voluntary conservation with the help of incentive programs. Recommended conservation practices are selected based on management intentions as well as the contribution of those practices to the overall net returns. However, conservation motives are heterogeneous and based on individual risk behavior. Existing cost-share programs might either under-fund or over-fund conservation, which could lead to inefficient management of natural resources. The current analysis evaluates the economic feasibility of variable cover crop strategies, multiple seeding rates, within a soybean production system in silt loam and clay soils. The study utilizes stochastic efficiency with respect to a function, referred to as SERF, for determining the preferred strategies under various risk preferences. The SERF method accounts for the heterogeneity of individual decision-making with regards to conservation adoption. Results indicate that most risk-averse farmers chose tillage radish with medium seeding rate as their preferred strategy. However, as the risk-bearing capacity of an individual increases, the current level of incentives does not motivate to implement conservation. The most preferred plan for risk-neutral farmers is the fallow system in both silt loam and clay soils. The economic and risk assessment framework can improve understanding of the temporal dynamics of different practices and inform policy on conservation structure that promotes agricultural systems that are economically, environmentally, and socially sustainable.

The strategy and associated practical details are described of a research programme which seeks to make effective use of controlled environment facilities in providing information and screening techniques useful to lentil breeders. Two principal objectives were (a) that genotypes grown in artificial climates should respond to whatever factors are being investigated in a manner which reflects their responses and relative sensitivity to different agroclimates in the field, and (b) to deploy controlled environment facilities for the longest period which is feasible during each calendar year and with maximum benefit:cost ratio.

The best time to plant Calliandra calothyrsus in association with Pennisetum purpureum and the appropriate in-row spacing of Calliandra for fodder and fuelwood production when grown on contour bunds were investigated. Main plot treatments were Pennisetum planted in November 1988 and associated with Calliandra in February 1989, Calliandra planted in November 1988 and associated with Pennisetum in February 1989, and both species planted simultaneously in November 1988. Sub-plot treatments were three within-row spacings of Calliandra. Survival of neither species was affected by time of planting. Total treatment yields of the second and third years were not influenced by time of planting but lower yields of leaf and wood were obtained from the later-planted Calliandra. Total yields were not significantly influenced by the spacing, but leaf and wood yields of the Calliandra at the 25 cm spacing were greater than those at the 100 cm spacing although not significantly different from those at the 50 cm spacing. Neither the time of planting nor the spacing of Calliandra affected the yield of maize or beans grown in the interbund areas. Simultaneous planting of Calliandra and Pennisetum is recommended.

This paper describes an attempt to develop and evaluate agricultural extension materials that support farmers' use of flexible management strategies. On the basis of experiment station and on-farm research results relating to millet and cowpea intercropping in Niger, a series of recommendations was developed, taking the form of a decision tree. The process of testing this format at the level of field extension agents and the implications of this experience for both research and extension workers are described.

Crop production surveys, which integrate the collection of data on both agronomic and economic variables, are increasingly common in on-farm research. A conceptual framework for designing and analysing such surveys is provided. Methodological issues in conducting crop production surveys are reviewed with respect to type of information collected, level of field observation, degree of quantification, frequency of observation, sampling, measurement of yields and yield components, and analysis of yield limiting factors. It is concluded that, while better integration of agronomic and economic perspectives in diagnosis may increase costs, the information and analysis obtained have considerable potential to improve the efficiency of experimentation.