An experiment was conducted in 1964 and 1965 to study the effects of hormone sprays on pod setting, pod filling and grain yield of black gram. Sprays of 2-naphthoxyacetic acid and p-chlorophenoxyacetic acid, alone and in 'mixture, and gibberellic acid and 1-naphthaleneacetic acid increased pod setting, but grain filling in pods and grain size were only slightly improved. 2-naphthoxyacetic acid gave the highest yield, followed by p-chlorophenoxyacetic acid, 1-naphthaleneacetic acid and a mixture of the first two, which increased yield by 56, 39, 36 and 35 per cent respectively over the control and gave economic returns.

A field experiment evaluating criteria for scheduling wheat irrigation was conducted from 1975 to 1977 in a sandy loam soil with treatments scheduled according to physiological stages, soil moisture conditions, pan evaporation and leaf water potential. Grain and straw yields, spikes/m, fertile spikelets/spike and number and weight of grains/spike were significantly influenced by treatments. Irrigation based on leaf water potential was as good as when based on physiological stages or soil moisture, and the use of pan evaporation was no better than other methods of scheduling.

The use of fertilisers in maize production has been the focus for many years of agronomic studies on research stations in East Africa. However, information on production risks and profitability of fertiliser use on smallholder farms is generally lacking because most of the early studies have focused on mean yields and yield components on research stations. This study applied rigorous analyses to determine conditions under which (1) production risks are low; (2) the recommended nitrogen (N) and phosphorus (P) fertiliser rates achieve a yield target of ≥3 t ha−1 believed to be a necessary condition to kick start a smallholder-led ‘green revolution’ in Africa and (3) N and P fertiliser use is profitable on smallholder farms in East Africa. Analysis of data from 464 on-farm trials in Kenya, Rwanda, Tanzania and Uganda revealed significant variations in production risks and nutrient use efficiency with season and soil type. On most sites, except in Uganda, production risks were lower with the recommended N and P fertilisers than the control during both the short and long rains. Production risks were three to four times higher with N and P fertiliser relative to the control on Lixisols and Ferralsols, but such risks were much lower on Nitisols, Leptosols, Vertisols, Plinthosols and Cambisols. The probability of exceeding grain yields of 3 t ha−1 with the recommended N and P rates was over 0.60 on Nitisols and Leptosols, but less than 0.20 on Lixisols and Plinthosols. The agronomic use efficiencies of N (AEN), P (AEP) and value cost ratios (VCR) were highest on Cambisols and lowest on Plinthosols. The VCR increased linearly with increase in AEN (R2 = 0.92) and AEP (R2 = 0.87) and less so with increase in grain yields (R2 = 0.47–0.60). Net present values indicated profitably of N and P fertiliser over the long term in only 30% of the site by season combinations in Uganda compared with 69% in Kenya, 81% in Rwanda and 84% in Tanzania. Patterns of N use efficiencies were different from P use efficiencies across soil types. Therefore, we recommend that N and P fertilisers should be appropriately targeted to soils where applied nutrients are used efficiently by maize crops.

Evaluation of agricultural Research, Development, Extension and Management requires knowledge of farming systems economics and risk as well as broader adoption drivers. But until now, these factors have not been effectively combined when determining the success of agricultural research projects. To fill this gap, we developed Value-Ag, an integrated modelling platform using whole-farm economic analysis and prediction of the scaling potential in the context of production risk and household dynamics to provide an ex-ante estimate of the benefits of adopting an innovation. In this paper, we use a hypothetical case study to illustrate Value-Ag’s potential to evaluate agricultural innovations in a rigorous, systematic and participatory manner across a range of scenarios, thereby stimulating thinking and learning opportunities with the relevant stakeholders, and increasing the scrutiny of projects so that they deliver greater value for money while fostering a more results-focused culture in developing countries.

The problems arising in field trials in plant pathology and entomology are considered under five headings: (1) experimental design, (2) conduct of experiments, (3) records, (4) analysis and (5) interpretation. Solutions to the problems are not always given, but it is useful to recognize their existence. Examples are given from a wide range of crops

In a trial carried out in 1958, aldrin applied as a fog with a swingfog machine at concentrations of 10 and 20 per cent in gas oil was more effective than dieldrin or chlordane at similar concentrations for control of Atta cephalotes. Two applications of 10 and 20 per cent benzene hexachloride and toxaphene failed to give complete control. In a subsequent trial, aldrin in concentrations ranging from 2·5 to 8·0 per cent was also found to be effective against A. cephalotes but against A. laevigata, aldrin and dieldrin were more effective than chlordane at concentrations of 5·0 and 2·5 per cent. In campaigns carried out from 1959 to 1963, 5000 nests were destroyed by fogging with 2·5 per cent aldrin in gas oil.

Experimental Agriculture (1997), 33, 367–383.

An incorrect version of Fig. 1(b) was published on page 373 of the above mentioned paper. The correct version appears below. The publisher apologises for this error.

Poor drainage of Vertisols in the Ethiopian mid-altitude highlands limits farming operations and cropping in the early rainy season (July–August). Traditional crops are grown on residual moisture late in the season (September–January) when waterlogging is less of a problem. Productivity is therefore below its potential. The recent introduction of a broadbed and furrow system for improved drainage on Vertisols allows full use of the growing period and provides scope for a wider variety of cropping systems and increased productivity. Trials using a sequential cropping system demonstrated that two crops a year can be grown when Vertisols are drained. The crops used in the trial were oats or an oat/vetch mixture forage in the early season followed by grasspea or chickpea food crops in the late season as the second crop. Further on-farm research on sequential cropping of forages and food crops in the mid-altitude highlands of Ethiopia is now needed.

Yield of swamp rice on acid sulphur soil was increased by liming and could be related to soil pH but was unaffected by drainage and differences in H2S in the soil. The seedling stage was most sensitive to acid and yield could be dramatically improved by planting mature vigorous seedlings. Survival of seedlings, tillering and panicle formation were the most important yield components affected by liming and acidity. Liming also increased spikelet number and grain size to a lesser degree. The optimal economic lime level for 3-week seedlings was around 4 t/ha but could be lower with 5-week seedlings.

To study control of Hemileia vastatrix leaf disease in Coffea arabica L., an experiment was run for a year in Coorg District of Mysore State. Three and four early-season sprays coupled with two mid-season ones gave a reasonable control, as evaluated by leaf spot counts, but a high proportion of rust-affected leaves were retained on the bushes. Infection commenced in the hot weather, immediately after showers, and the number of infected leaves appears to have been more important than the average leaf spot counts. Control of leaf disease up to December, and a late incidence of the rust during January, may not affect crop prospects appreciably. It is suggested that reduced early sprays coupled with pre-monsoon and timely mid-season schedules should reasonably control the incidence of rust.

A field experiment was conducted during the monsoon seasons of 1982 to 1984 to investigate the effect of chlormequat chloride (CCC) and its mode and time of application on groundnut. Foliar application of CCC 60 days after sowing at the rate of 200 ppm reduced moisture loss and increased relative leaf water content and yield. Soaking seed in a 0.5% CCC solution also increased relative leaf water content, root nodulation and seed yield.

A procedure was used to calibrate the DSSATv3 CERES–Maize (Zea mays) model and to evaluate its performance in simulating growth and development of maize using input data collected from campesino farmers instead of using data obtained from on-station experiments or from the literature. The problems encountered in the calibration process are illustrated, particularly the failure of the model to simulate the growth and development of local highland maize cultivars (HMC). It is argued that the low ambient temperatures to which HMCs are exposed in the Toluca Valley are responsible for this failure, because HMCs respond differently to temperature and have a different optimum temperature range from temperate and tropical maize cultivars. It was concluded that the model needs to be adjusted to allow for consideration of the effects of constant low temperatures on the prediction of plant phenology and production, and partition of biomass in HMCs, since grain yield is not the main criterion used by smallholders when selecting maize cultivars.

Studies to determine the effect of planting unshelled pods, using groundnut varieties with different shell thicknesses, indicated that emergence and yield were suppressed by planting unshelled pods. Depth of sowing, and soaking pods in water prior to planting, had limited effects.

Bread wheat is grown under irrigation in Saudi Arabia. Since water resources are limited, any additional agricultural development must make use of sources of water that are less than ideal, for example, saline drainage water. A two year field study was conducted to compare the effects of irrigating bread wheat with normal water, with a 1: 1 mixture of normal water and drainage water, and with drainage water alone, at three levels of nitrogen fertilizer use. The mean electrical conductivity of the irrigation water was 2.6, 8.6 and 14.6 ds m−1, respectively, in the two seasons of the study. Irrigation with drainage water decreased yield and yield components but increased the protein content of the grain of the two wheat cultivars studied. Drainage water depressed straw yields more than it depressed the yield of grain. Nitrogen application increased yield and yield components in all the irrigation treatments, partially overcoming the adverse effects of the use of saline drainage water.

Efectos del agua salada y el nitrógeno en el trigo

A study conducted at Ibadan, Nigeria, showed that some community water supplies were slightly polluted by the pesticides applied on adjacent farms. There was also evidence of soil degradation as a result of agrochemical use, with differences in the physico-chemical properties of soils in fields where agrochemicals had been applied and in adjacent fields that had not been cultivated. Measures that can be taken to minimize some of the environmental dangers inherent in the application of agrochemicals are discussed.

Genetic engineering of crop plants has been in progress since the dawn of agriculture, about 10 000 years ago. For millennia the genetic make-up of our crop plants has been changed by mankind's selection of naturally occurring variants. As the trade routes were developed, novel plant types were introduced into new environments and provided more variation from which to choose. At the end of the nineteenth century an understanding of the laws of heredity was gained and plant breeding protocols were devised whereby selection became accompanied by deliberate crossing. As the knowledge of the genetic structure of crop plants improved, new ways of manipulation were invented and exploited. Indeed plant breeding became a testing bed for new ideas in genetics. For the plant breeder the techniques which were most widely employed in the past were those which aided breeding, for example techniques which speeded up the production of new varieties, but still used traditional routes of crossing and selection. This was a transitional phase between plant breeding as an art and plant breeding as a science.

A field experiment to study weed and fertility management in rain-fed maize was undertaken at the Palampur Experimental Farm during the wet seasons of 1977 and 1978. Intercropping soya-bean in maize did not impose undue competition and significantly increased net profit per ha. Yields and net returns were significantly higher when weeds were controlled and 80 kg N/ha was applied. Increased application of fertilizer without weed control did not alter the yield of maize, and there was no response to phosphorus. Various yield attributes of maize were significantly affected by weeding and nitrogen treatments through their effects on grain and stover.