A method of obtaining the standard error and some other moments for the ratios of biological measurements is given, with the conditions to be satisfied by the variables used to form such ratios. Some applications of the distributional properties of the ratios in the analysis of results from experiments are discussed.

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.

Nitrogen-atrazine combinations were significantly more effective in stimulating higher yield components of sorghum and depressing yield components of striga than sole treatments of either nitrogen or atrazine. Over all treatments nitrophoska at 129 kg N/ha in combination with atrazine at 1.75 kg/ha gave 224, 180, 155 and 151% increases in yield components over the control for head, straw, 1000 grain weights and plant height of sorghum, and a decrease in 83, 88 and 90% of striga density at 8, 12, and 16 weeks from sowing the sorghum. The synergistic effect of nitrogen-atrazine is demonstrated.

The effect of different soil temperatures on the development of young eggplants was examined at extreme seasonal air temperatures. In winter, rising soil temperatures accelerated growth, but lowering the soil temperature in summer had no effect and extremely high soil temperatures caused very poor plant development.

The effects of day length extension and night interruption on flowering responses of St John's Wort (Hypericum perforatum) plants were investigated. Field-grown plants were subjected to five different day lengths (11, 13, 15, 17 and 19 h d−1) or night interruption for 70 days. The results indicated that St John's Wort is a long-day plant requiring a critical day length of 15 hd−1 for flowering induction. Both day length extension (duration longer than 15 h) and night interruption, with artificial light (fluorescent lamps that delivered 30 μmol m−2 s−1 photosynthetic photon flux density at plant height) were effective for flowering induction and seed setting. Day length extension or night interruption experienced by the maternal plant also affected the germination responses of the seeds produced. Plants that had received 19 h of day length treatment produced seeds with better germination responses. Night interruption with daylight type fluorescent lamps was also effective for producing relatively high quality seeds, although these seeds had slightly lower germination rates and longer mean germination time than seeds produced under 19 h of day length. Such a night interruption system could be considered for seed production of St John's Wort on a commercial scale.

Greater yam (Dioscorea alata), a popular crop in India, is cultivated widely in Orissa state, India. In spite of the availability of several improved varieties, farmers preferred the local landraces. An investigation was carried out to identify whether the varietal preferences of yam farmers in two production systems, subsistence and commercial, were different. While the subsistence farmers demanded the yam varieties adaptable to a wide range of soils, the commercial farmers preferred the anthracnose-resistant cultivars. This study demonstrated that the farmers' varietal preferences were highly influenced by the production systems. Identifying the convergence/divergence of varietal preferences across production systems can help breeders to develop the high impact varieties.

Visual symptoms of deficiencies of nitrogen, phosphorus, potassium, calcium, magnesium, sulphur and boron on pyrethrum are described, and compared with those observed previously on other species of chrysanthemum.

The object of the study was to find whether loss during combine harvesting was correlated with pod shattering propensity of soybeans. Mechanical pod shattering methods tested included vibration, impact, centrifugation, pod traction and compression. The influence of variety and moisture content on mechanically-induced pod shatter and on header losses was studied. The pod suture compression method was simplest to perform and, with respect to crop moisture, gave results indicative of machine harvest shatter levels. Such a standardized mechanical shatter index may prove a useful criterion in soybean breeding selection for harvest shatter resistance.

At Ukiriguru, in Western Tanzania, three levels of sulphate of ammonia were compared on natural pastures on hardpan soils. Yields of dry matter were substantially increased by nitrogen fertilizer and at high stocking rates the growth of cattle on different treatments followed fairly closely the amounts of dry matter available.

An extended assumption in maize breeding is that potential yield (Ymax) predicts yield (Y) under stress conditions (here, Ymin), justifying genotypic selection under moderately high-yielding environments. Moreover, it has been postulated that Y tolerance to stress is relatively independent on the main stress factor involved in Y reduction (cross-tolerance). We carried out an analysis of four datasets from Argentine Federated Farmers network (2010/11, 2011/12 and 2012/13, 11 locations and >20 hybrids) and the National Institute of Agricultural Technology (INTA) (12 locations, 13 hybrids). No consistent relation was detected between Ymax and Ymin (r2 < 0.14) in each dataset. Y stability assessed by the coefficient of variation positively related to Ymin (r2 > 0.68 across datasets) but not to Ymax. Depending on the dataset, 40–70% of the hybrids had a varying Y performance (from worse to better) compared with the average of all hybrids, with no consistent advantage of hybrids with high Ymax within the environmental range explored in the dataset. In order to assess the existence of cross-tolerance, INTA environments were divided into two groups: water-limited environments and environments exposed to other(s) type(s) of stress. While a relation was found between average yields (r2 = 0.64) of each hybrid in both environments, there was no relation for Y stability (r2 = 0.07). Taken together, our results suggest that: (i) a high Ymax is not a good indicator of high Y tolerance under stressful conditions; (ii) Y tolerance is related to high Y stability, which may or may not involve a Y penalty under high-yielding environments; (iii) around 50% of the genotypes have Y performance that is not consistently worse or better than the average throughout the range of environments explored and (iv) cross-tolerance to stress is a peculiar trait of some hybrids, but most of the hybrids analysed here do not show cross-tolerance.

Rapid initiation and growth of nodal roots (NR) are critical for the establishment of post-rainy season (rabi) sorghums grown in drying soil. The growth of NR was studied in sorghum in the field when sown at different depths in order to vary the crown depth, when different levels of irrigation water were applied to create different moisture contents in the topsoil, and in a number of cultivars to assess genotypic variability. Variation in sowing depth did not result in differences in NR growth, partly because of the capacity of sorghum to vary the mesocotyl length, which brought the crown to approximately the same depth. Different soil moisture levels in the field affected the elongation rate of NR, but not their initiation. Genotypic variation existed in the thermal time required for NR initiation and rate of elongation. The variation in NR growth was independent of the variation in shoot growth. The genotypic variability in NR growth offers an opportunity for combining root-related traits with useful agronomic characters.

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.

Ten tomato varieties, tested at three locations for 3 years in Western Nigeria, gave variety × environment interactions, indicating that some were only suitable for specific areas and none possessed wide adaptation. It is suggested that Western Nigeria could usefully be divided into sub-zones in which specific varieties could be developed.

A simple method of studying the reaction of detached cacao pods to Phytophthora palmivora is described. The results, which bear a close relation to field observations, are discussed in this context.

Ammonium has been reported as a ‘preferred’ nitrogen (N) source for sugarcane (Saccharum spp.), which can improve N use efficiency (NUE) in this crop. We aimed to evaluate the preferential uptake of ammonium and nitrate in sugarcane genotypes contrasting with NUE under controlled conditions. Four sugarcane genotypes previously selected by another experiment (ER: efficient and responsive; ENR: efficient and nonresponsive; IR: inefficient and responsive; INR: inefficient and nonresponsive) were grown in a growth chamber and fertilized with two 15N-labeled forms [(NH4)2SO4 (15N-NH4+) or KNO3 (15N-NO3−)]; soil was used as substrate. Plants were evaluated at three time points: 0, 24, and 72 h after 15N-fertilization. For the efficient genotypes (ER and ENR), the soil NH4+ levels were about 20% lower than those found for the inefficient genotypes (IR and INR) indicating greater N extraction by the plant. Nitrogen derived from fertilizer (NDFF) and 15N recovery from fertilizer (15N RFF) in roots were influenced by the genotypes, in which responsive genotypes (ER and IR) presented a mean value 40% higher than the genotype INR, showing that greater absorption is more related to response than efficiency. Three days after N application, NDFF and 15N RFF from 15N-NH4+ were greater than 15N-NO3− in 40% and 65% for the roots and aerial part, respectively. The results of this study confirmed that sugarcane presents preferential uptake of NH4+ N form 3 days after fertilization. The use of nitrification inhibitors can be considered for providing a longer NH4+ residence time in the soil, also contributing to augmenting the NUE in sugarcane.