This paper reports the heterotic pod production of three different crosses between a Nigerian local selection (N38) and three Trinidad Introductions (CF47, CF56 and CF207). The hybrids consistently outyielded the inbreds throughout the first 19 years of pod production. N38 × CF56 hybrid produced the highest number of pods per tree, closely followed by N38 × CF47 hybrid; while N38 × CF47 hybrid showed the best heterotic response. Pod production figures of (CD207)2 and (CD302)2, both double inbreds of N38, support the hypothesis that N38 is a Trinitario × local selection hybrid which segregate for pod production.

The photothermal flowering responses of 25 diverse genotypes of common bean (Phaseolus vulgaris L.) were examined in 25 African Bean Yield Adaptation Nurseries (AFBYAN) in the Eastern, Southern and Great Lakes regions of Africa during 1988 and 1991. The trials were located at latitudes between 0.6 and 29.3° and at altitudes from 780 to 2200 m asl. In those 13 trials where daily records of maximum and minimum temperature were available, mean pre-flowering temperatures for individual genotypes ranged from 17.9 to 24.6 °C and mean pre-flowering photoperiods varied from 12.7 to 14.7 h d−1. The time from sowing to first flowering (f) for the 25 genotypes varied from 26 to 42 d in the most-inductive regime to as late as 47 to 80 d in the least-inductive circumstances. The stepwise linear regression on daily mean temperature during the pre-flowering period explained most (52–86%) of the variation in the rate of progress from sowing towards flowering of 21 genotypes. In contrast, in four genotypes (GLPx 92, Ikinimba, G 13671 and G 2816) the fitted values of days to flowering using temperature alone were much earlier than the times observed in the two trials at Maseru in Lesotho (the highest latitude and coolest location). These differences may well reflect photoperiodic effects but from the photothermal combinations encountered this could not be confirmed and so remains to be proven. The overall mean absolute difference between the observed and fitted time to flowering was just 2.6 d. The estimated optimum temperatures ranged from 20.4 to 23.3 °C, at which the minimum times taken to flower were between 28 and 44 d. The derived base and ceiling temperatures ranged from 7.1 to 13.2 °C and from 29.1 to 40.2 °C respectively. Not surprisingly, the use of long-term monthly temperatures (for those trials from which daily temperature records were not available) gave poor agreement between predicted and observed flowering times. The significance and implications of these findings are discussed in relation to those from other studies on the photothermal flowering responses in common bean and the breeding and testing of common beans in Africa.

The ureides allantoic acid and allantoin form a bright pink compound with acidic p-dimethylamino cinnamaldehyde. It is possible to estimate the ureide content of a soyabean petiole segment by crushing it on filter paper and developing the colour with this reagent. There is a strong correlation between the spot test and estimates from colorimetric determination of ureides. In field grown soyabeans, there was a positive correlation between the petiole ureide content during pod fill and the integrated seasonal acetylene reduction activity. The spot test can be used to identify plants with low nitrogen fixation activity.

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 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.

A number of crosses were made to study the mode of inheritance of flower colour and number of locules per capsule of sesame. Red flower colour was dominant to white, and 4-loculed dominant over 8-loculed pods, each of the traits being controlled by a single gene pair segregating in a 3:1 F2 ratio.

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.

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.

Field experiments were conducted for 4 years to study the yield of ‘kharif’ and ‘rabi’ crops grown in sequence on two soils differing in water-holding capacity. The results indicated that drought caused greater reduction in yield of rainy-season crops on loamy sand than on sandy loam soil. In low retentivity soil it was more profitable to raise a single crop of wheat on soil-stored water. In sandy loam soil of higher retentivity, two crops a year gave much higher yields than a single crop. Of the sequences tried, maize followed by wheat gave the highest and most stable yields. For ‘rabi’ crops, stored water showed a better yield response than an equivalent amount of rain during the growing season.

Effects of moisture stress during different stages of cotton development were evaluated by using correlation and regression methods on data of six irrigation experiments from three different climatic regions. Significant negative correlations were found between the number of days in which soil moisture was below a threshold level, and several plant traits. Flower number was usually affected adversely by stress at the beginning of flowering; boll number, boll retention, boll weight, lint yield, lint length and seed index by stress at the end of flowering; earliness and lint fineness by stress during early boll development. Lint index, per cent and strength were affected by stress at different periods and effects of stress on lint yield were correlated with its effects on boll number, boll weight, lint length and early maturity.

Studies of seed pelleting and liming for legume establishment at initial low pH levels in prepared seedbed and natural pasture situations were conducted in 1971 and 1972 at Rio Grande do Sul, Brazil. Lime-pelleted seed often improved establishment and increased subsequent dry matter herbage yield of soybeans, greenleaf desmodium, and perennial soybeans at low pH levels (4·8 and 4·9) and low lime rates. Applying agricultural lime at rates up to 6 t/ha generally improved legume establishment and herbage yields on prepared land or in disked natural grass sod, compared to unlimed areas.

Dry matter production in a bushy and spreading cultivar of sweet potato was studied in two trials comparing dry matter partitioning between plant components. The bushy cultivar, VSP-2, accumulated more tuber dry matter than the spreading cultivar, BNAS-51. The number and yield of tubers of VSP-2, was also greater but its foliage dry weight was less than that of BNAS-51. The vine and root dry weight of BNAS-51 increased with time but that of VSP-2 reached a peak about 10–12 weeks after planting. The tuber dry weight of BNAS-51 at harvest was similar to its foliage dry weight but that of VSP-2 was three times greater. The proportion of total dry matter partitioned to the tubers of VSP-2 was greater than that in BNAS-51 at all stages of growth.

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.

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.

The effect on Coffea arabica cv. Ruiru 11 of training the trees on a single or two stem system at planting densities of between 1600 and 4800 trees ha−1 during the first production cycle after establishment was studied at three contrasting sites in Kenya. Training tree growth in the two stem system significantly depressed yields from the first two crops at all sites, irrespective of plant density, but yields caught up with the production levels of the single stem system faster in the wetter than in the drier zone. Yields of clean coffee increased with tree density up to 4000 trees ha−1 at all sites, irrespective of tree training method, but increased more slowly at populations of more than 4000 trees ha−1, especially in the drier zone. The proportion of large, grade A, coffee beans was not significantly influenced by the treatments studied.