Three Nigerian vegetables, Solanum melongena, Solanum nodiflorum and Vernonia amygdalina were analysed for oxalate, cyanide, minerals and food value. The edible leaves were low in oxalate and so involve no danger of oxalate toxicity, or decrease in their nutritive value due to the presence of oxalic acid. The content of hydrocyanic acid was also negligible and would, in any case, be lost during cooking. Aluminium contents were very high and could possibly be regarded as constituting a toxic level. The calcium content would provide about 4–7 per cent of the daily requirement for adults, who could depend solely on these vegetables for their daily iron requiretnents. The leaves were also good sources of protein. All these factors make the vegetables important dietary components in Nigeria and they could serve as a protein supplement, especially in villages where children can not get enough protein from meat, milk and cheese.

The impact of a 20-year-old cashew plantation on a forest soil was evaluated by comparing the properties of soil under cashew with that under an adjoining logged rain forest. The levels of organic carbon, nitrogen, exchangeable calcium and magnesium, and available phosphorus were similar under logged forest and cashew, suggesting that organic matter and nutrient cycles in a cashew plantation are similar to those in a logged rain forest and that cashew has no significant adverse effect on soil organic matter and nutrient status.

Bulbs of 20 onion cultivars were stored at 30°C and assessed for rotting and sprouting. No evidence of heritable resistance to high-temperature rotting was found, but the suppression of sprouting by high temperatures appeared to be a common character of onion cultivars.

The effects of moisture stress at various stages of development were studied on two varieties of cotton in the arid Negev region of Israel. Experiments over two years indicated that the stage at which moisture stress occurred determined its effect: when at the beginning of flowering, yield was considerably reduced; at the peak of flowering there was a less pronounced effect; and when stress occurred during boll development it had an effect in only one year, when reserves of moisture in the deep soil layers were low. Lint yield ranged from 380 kg./ha. without irrigation to 2150 kg./ha. with five irrigations. Effects on lint length and lint strength were also studied. Two physiological indices, stomatal aperture and refractive index of leaf sap, were used to determine the onset of moisture stress.

The effect on maize yields of ground rock phosphate, alone or mixed with sulphur in either of two proportions, and of single-superphosphate, was measured at five consecutive harvests. At the first harvest single-superphosphate increased yield by 1.54 t and the best of the mixtures by 0.56 t grain/ha. Ground rock phosphate alone had no effect on yield. At the third harvest there were no yield differences between sources; because yields produced by rock phosphate and the mixtures improved. The cumulative increase in yield produced by single-superphosphate was 3.58 t/ha and by rock phosphate 2.69 t grain/ha, but because the fertilizer cost ratio was 3:1, additional grain produced by rock phosphate cost half as much. The apparent P recovery ranged from 5.40 to 8.28 kg/ha, with most from single-superphosphate and least from the mixture containing most elemental-S.

Under the arid tropical conditions of the Sudan, where seasonal variations in photoperiod are small but where temperatures are high, there is evidence from the performance of both local and introduced onion varieties that temperature has considerable influence on bulbing. The onset of bulbing does not prohibit the emergence of bladed leaves under such high temperature conditions. The size of the onion plant may be an important factor in the bulbing response under conditions of high temperature and small variations in photoperiod.

A diallel analysis of flowering time, pod number, 100-seed weight and yield of six cultivars of Cajanus cajan (L.) Millsp. was studied. Additive inheritance was important in determining flowering time, but the dominance component was higher than the additive component, and over-dominance was observed for pod number, 100-seed weight and yield. Heritability estimates for all the traits except flowering time were quite low, and the bulk population method of breeding was suggested for early segregating generations. The graphical analysis of the diallel cross was in close agreement with the findings from variance component analysis. It is suggested that the best cross would be that between two parents chosen on the basis of their low g.c.a. for flowering time and their high g.c.a. for other traits.

Uptake of nitrogen, phosphorus and potassium was measured for irrigated and unirrigated crops of pearl millet grown at Hyderabad, India. Irrigation slightly increased the concentration of nutrients in the crop and this, together with a higher dry weight, resulted in the nutrient content at harvest (day 82) being approximately twice that of the dry crop. Nutrient uptake by the latter ceased at about day 40 whereas the irrigated crop continued to take up nutrients for a further 7–21 days. However, both crops showed the importance of redistribution of nutrients from leaves and stems during the grain filling. The mean rate of nutrient uptake per metre of root per day (inflow) fell throughout growth in contrast with the rate of nutrient uptake per plant, which reached a maximum at about days 26 to 33. These findings are discussed in relation to possible strategies for fertilizer placement.

Early season defoliation of maize significantly reduced plant height and leaf area index but leaf number and leaf emergence rate were not affected. Ear development was significantly affected by both early and late season defoliation although tassel development was barely influenced. Silk growth was the phase of ear development most sensitive to defoliation. Early season defoliation significantly reduced all yield components, leading to yield losses ranging from 54 to 100%. The position of the leaves which were removed had an important effect on the final grain yield. Harvest index was affected by both the intensity and timing of defoliation.

Effects of sowing dates, population, fertilizer, weeding and variety inputs on yield were measured, as well as labour required to apply the inputs. Sowing date was the most important, response to others being dependent upon this factor. Population was least important, but increased in value as fertilizer level was raised. Labour requirements were so increased by applying the ‘package’ that subsistence farmers, whose families are fully occupied as the sole source of labour, would be unable to cope without reducing the area under cultivation. Thus yield response to a package must be higher than hitherto considered acceptable, and the risk of not obtaining this increase probably contributes to the rejection of such recommendations by subsistence farmers.

A study was made of the nitrogen fixing systems of various forage legumes and their rotational effect on yield of subsequent cotton crops, as well as of yields of the different legumes. Phillipe-sara, clitoria and lubia out-yielded all the others. Nitrogen yields of the various forage legumes showed that they are active fixers of atmospheric nitrogen, but yields of cotton following the various legumes showed wide seasonal variability and were neither significantly nor consistently different in different seasons. On the other hand, the increase in cotton yield due to fertilizer nitrogen was highly significant, indicating a comparatively small end-of-season contribution of cut legumes to soil nitrogen. It was therefore difficult to differentiate between the legumes on the basis of any consistent ability to influence yields of following cotton, suggesting that the choice of a legume in the rotation should depend primarily on economic considerations.

A study was conducted from October 1994 to March 1996 to assess groundwater dynamics and quality in relation to landuse and farm input of nitrogen fertilizer in a highly diversified and intensive agricultural area at Magnuang, Batac, Ilocos Norte. Monthly groundwater depths, nitrate-nitrogen (NO3-N), chloride (Cl−), bicarbonate (HCO3−), electrical conductivity (EC) and pH were determined in 19 agricultural and domestic wells. In the dry season, sweet pepper (Capsicum annuum) had a higher irrigation requirement and caused more groundwater level decline than other crops. EC (700–3000 μmho cm−1) and HCO3− (90–500 ppm) in all wells exceeded the FAO threshold quality for irrigation but were not related to farm management practices. Eight wells showed near or above the World Health Organization NO3-N limit (10 ppm) for drinking water. High nitrogen fertilizer input increased the mean NO3-N (r2 = 0.45, p < 0.002). The percentage of the wells' service area under rice cultivation in the wet season accounted for 84% (p < 0.001) of the variation in NO3-N among the wells. The mean NO3-N declined as the percentage of service area under rice increased. This was related to the denitrification process in the flooded fields and the lower levels of nitrogen fertilizer for rice compared with other crops.

Ex-situ collections of vegetatively propagated root crops are difficult to maintain in developing countries. On-farm conservation could be a solution but is more complex for vegetatively propagated than for sexually propagated species. In Vanuatu, a Melanesian archipelago where yam, taro, sweet potato and cassava are staples, a study was undertaken to develop an on-farm conservation system based on the geographic distribution of allelic diversity. Two years after the introduction of new varieties, a survey was conducted with 449 farmers located on 10 different islands. In order to evaluate on-farm conservation efficiency, qualitative and quantitative investigations were conducted and data were analysed. The conclusion was that farmers do enrich their varietal portfolios with introduced exotic genotypes thus broadening the narrow genetic bases of some species. Nevertheless, no local varieties were lost. Significant geographic distribution of clones of new varieties throughout the archipelago also took place via spontaneous, informal distribution to farmers' relatives. These encouraging results point to the potential impact of the geographic distribution of allelic diversity on smallholders' varietal portfolios. On-farm conservation appears to be an appropriate strategy for the conservation of root crop germplasm diversity in Vanuatu. Potential applications for transfer of the methodology to other locations are discussed.

This paper presents the results of extensive experience in the development and promotion of tobacco-based insecticides for the control of field crop pests in Igalaland, Nigeria. A non-governmental organization (NGO), the Diocesan Development Services (DDS), became involved in the development of tobacco-based insecticides in the early 1990s, and facilitated a series of ‘on-farm’ trials between 1997 and 2000 designed to test the effectiveness of such insecticides for two crops that are particularly vulnerable to pest attack in Igalaland: cowpea (Vigna unguiculata) and maize (Zea mays). The results suggest that even crude tobacco formulations had a significant benefit on cowpea and maize yields relative to the absence of pest control, although commercial insecticides were more effective. However, while having advantages of cost and availability over commercial insecticides, tobacco-based products appear to have serious internal and external disadvantages that limit their widespread use, and some of these are discussed. It is concluded that while technical efficacy of botanicals is an important element, there are others such as the logistics of production and preparation that need to be considered. A better understanding of the balance between these factors and how context-specific they may be is required in order to maximize their adoption by farmers under ‘resource-poor’ conditions.

Fertilizer nitrogen (N) management in any region following standard general recommendations discount the fact that crop response to N varies between sites and seasons. To devise field-specific N management in wheat at jointing stage (Feekes 6 growth stage) using atLeaf meter and leaf colour chart (LCC), eight field experiments were conducted in three wheat seasons during 2017–2020 in the West Delta of Egypt. In the first two seasons, four experiments consisted of treatments with a range of fertilizer N application levels from 0 to 320 kg N ha−1. Monitoring atLeaf and LCC measurements at Feekes 6 growth stage in plots with different yield potentials allowed formulation of different criteria to apply field-specific and crop need-based fertilizer N doses. In the four experiments conducted in the third season in 2019/20, different field-specific N management strategies formulated in 2017/18 and 2018/19 wheat seasons were evaluated. In the atLeaf-based fertilizer N management experiment, prescriptive application of 40 kg N ha−1 at 10 days after seeding (DAS) and 60 kg N ha−1 at 30 DAS followed by application of an adjustable dose at Feekes 6 stage computed by multiplying the difference of atLeaf measurements of the test plot and the N-sufficient plot with 42.25 (as derived from the functional model developed in this study), resulted in grain yield similar or higher to that obtained by following the standard treatment. The LCC-based strategy to apply field-specific fertilizer N at Feekes 6 stage consisted of applying 150, 100 or 0 kg N ha−1 based on LCC shade equal to or less than 4, between 4 and 5 or equal to or more than 5, respectively. Both atLeaf- and LCC-based fertilizer N management strategies not only recorded the highest grain yield levels but also resulted in higher use efficiency with 57–60 kg N ha−1 in average less fertilizer use than the standard treatment.

A method is described for constructing a direct-reading scale for leaf area measurement of cereals. The scale is constructed from linear dimensions of leaves, and it enables rapid non-destructive measurements to be made.

Ten accessions of Napier grass (Pennisetum purpureum Schumach.) were evaluated for their dry matter (DM) yield and forage quality in a semi-arid lowland (Katumani) and a relatively wet highland (Muguga) over seven growth cycles from 2011 to 2013 in tropical Kenya. Three biomass yield clusters were identified from the 10 accessions as high-yielding (HYC), medium-yielding (MYC) and low-yielding (LYC) clusters for both sites. Total biomass (shoot and root) yields (t ha−1) over the seven growth cycles were 25.3 for HYC, 22.2 for MYC and 19.6 for LYC at Katumani and 40.0, 41.4 and 29.1 at Muguga. Total biomass yield averaged over the study period was DM 22.4 t ha−1 at Katumani and 36.8 at Muguga. Rainfall productivity was higher at Katumani (28.8 kg ha−1 mm−1) than 20.8 kg ha−1 mm−1 at Muguga. Neutral detergent fibre (NDF) was lower in LYC, which was more leafy than the other clusters and there was little difference in NDF between the two sites.

Comparisons of single cropping, double cropping and relay cropping of soyabeans (Glycine max) with wheat (Triticum aestivum) were made at two sites in Arkansas over a two-year period. The comparisons were made using both soyabean blends and their component cultivars. In relay cropping the yields of pure lines of soyabeans were reduced by 17% compared with single-cropped soyabeans, but the yield of wheat in relay cropping was 15% less than in double cropping. Double cropping reduced the branch number, plant height, node number and leaf area of soyabeans compared with single cropping, but relay cropping reduced only node number and leaf area. Both double cropping and relay cropping gave greater land equivalent ratio (LER) values than single cropping, and double cropping gave greater LER values than relay cropping. Net returns were lowest with single cropping and greatest with double cropping. Soyabean blends gave yields similar to the mean of the component genotypes in all three cropping systems, and the net returns of blends were similar to those of the means of component genotypes.

Maize was grown from three batches of seed, with mean 1000-grain weights of 225, 432 and 649 g. Initial plant size was larger when grown from large seed, but development rates were similar for all three sizes and relative growth rates were similar during the early stages. Relative differences in plant size became smaller as the crop matured. Crop growth rates during the linear phase of dry matter production were the same, and there were no significant yield differences. Comparisons of leaf and spikelet initiation, and individual leaf size are also reported.

The productivity, land equivalent ratios (LERs) and light use efficiency of a pear and radish interculture system were assessed. Pear yield was unaffected by intercropping. Relative yields for the radish component varied between 0.5–1.01 depending upon the yield index and spatial arrangement employed. This gave LER values for the system of 1.5–2.01. The overall trans-missivity of the pear canopy was 73%. A 47% reduction in photosynthetically active radiation (PAR) gave a yield reduction of 65% in terms of number of saleable radish, but did not affect total dry matter productivity. Reductions in radish yield directly beneath pear trees was thought to be due to other factors besides PAR. The total dry matter productivity of a system containing five successive radish crops was estimated at 26.25 tonnes ha−1 yr−1.