Yield stability in beans from diverse sources in Malawi was estimated using the statistical parameters of genotype X environment variance, slope and standard error from regression. The heterozygous F2 and the most complex synthetic mixture were very stable, although not significantly different from some pure genotypes. The mean yields of most mixtures were marginally higher than the average of their components. There was a linear relationship between magnitude of diversity and stability. Evidence for heterozygote advantage was demonstrated.

Component analysis was applied to the interpretation of (a) leaf analyses from six similar groundnut fertilizer trials, and (b) the chemical composition of different parts (root, stem and successive leaves) of the sugar cane plant. For each of the groundnut trials it was found that approximately 60 per cent of the total variation in N, P, K, and Ca could be accounted for by two independent linear functions of the elements, representing the balance of N and K with Ca and the balance of N with P and K. The second of these functions was consistently affected by phosphorus applications. Yield was related to one or other function, according to trial, but never to them both. Throughout the sugar cane plant the elements N, P, K, Ca, and Mg were found to be distributed between the roots and the aerial parts, and between active photosynthetic and non-photosynthetic tissues. In both cases the result was a reasonable and consistent simplification of a considerable body of data, such as had not resulted from a series of univariate analyses of variance.

Nitrogen (N) losses greater than 40% in furrow-irrigated cropping systems are a common problem that substantially limits yields. Sustainable production methods are therefore required to reduce these losses and increase the yield under semi-arid conditions. A field trial was carried out to study the soil N dynamics and soil physicochemical properties in soils amended with organic manure (i.e. with poultry manure (PM), farmyard manure (FYM) and pressmud compost (PrM)). Soil N dynamics and properties were evaluated under different ridge to furrow ratios (1:1 and 2:1) as well as maize yield and profitability. When ridge to furrow ratio increased (2:1) in soils amended with PM, the inorganic and organic N status was increased and N losses were reduced. This strategy lowered soil pH, and maximized organic matter status and maize yield. The highest yield, net income and benefit–cost ratio were attained with 2:1 ridge to furrow ratio and PM amendment, being an alternative management for increasing maize productivity and profitability while improving nutrient use efficiency.

Soil degradation is characterized by loss of soil organic matter, decline in fertility, imbalance in elemental content, deterioration of soil structure, and overall a deterioration of soil environment. According to the classification method of Pieri et al. (1992), the soil is classified into different degradation classes by calculating the soil structural stability index (St) of each sample point. We aimed to investigate changes in the contents, storages and stoichiometry of soil carbon (C), nitrogen (N), and phosphorus (P) together with changes in soil physical traits along a soil degradation gradient in jasmine croplands in Fuzhou area (China). The content and storage of soil C and N decreased with increasing intensity of land degradation. Soil organic C content was 15.4%, 32.3%, and 38.8% lower, respectively, in the low, medium, and high degree of degradation soils, than in the nondegraded soils. The soil C:N ratio was 18.5% higher in soils in the middle degree of degradation than in the nondegraded soils. Compared with nondegraded soils, the bulk density of the degraded soils increased and water content decreased. The decrease of soil pH coupled with salinity (conductivity) and the loss of aggregate stability are the main traits that distinguish degraded from nondegraded soils. We also detected a general N and P deficiency that is aggravated by the degradation process. Unreasonable management easily leads to degradation associated with a loss of organic C and total soil nutrients, thus impairing even more a general N and P deficiency in this area. Therefore, higher inputs of organic fertilizer should be added to alleviate the lack of organic matter, and appropriate burial should be conducted to reduce nutrient loss. Moreover, a rise of N and P fertilizer application is also advisable.

The design of a low cost and relocatable rain out shelter used for drought studies in the field is described. This design, covering 162.5 m2, enables reasonable plot sizes to be used and minimizes aerial and sub-aerial edge effects. A fully retractable vinyl cover results in minimal modification of the surrounding crop environment.

Latex flow can be stimulated by bark scraping and by the application of vegetable oils, auxins and some other substances to the bark, either above or below the tapping cut. Auxin preparations are now widely used in commercial rubber production, 2,4–D and 2,4–5–T being the most common. The response obtained depends upon the formulation, on the method of application, and on other factors such as the age and condition of the tree and the tapping system employed. The effect of stimulation is considered to be due to a dilution of the latex and an increased rate of flow. A larger area of bark is drained, and the duration of flow is prolonged, because plugging of the latex vessels is delayed. In young trees, the conflict between increased latex production and active tree growth requires the development of different and less intensive techniques.

The effect of spatial variation on experimental error variance and the significance of differences between genetic entries was evaluated in five performance trials. A significant portion of spatial variation could be detected in all the experiments investigated and various neighbour plot residuals were applied to adjust for local field trends. Neighbour plot adjustment was clearly more efficient than the randomized complete block design in reducing error variance and in detecting significant differences between entries. It was also more efficient than lattice designs in trial fields exhibiting short distance trends, which could not be covered efficiently by incomplete blocks. In most experiments with long and narrow plots, longitudinal adjustment using two neighbours at each side of a test plot was superior to adjustment by only one ‘nearest’ neighbour.

Increased use of prime agricultural land for cropping and non-agricultural uses in many tropical countries implies that crop residues become more important as a source of feed for livestock. Traditionally, much research on crop residue feeding was done by focusing on laboratory measurements of feed quality but neglect of farmers' perceptions led to disappointing results in the transfer of straw feeding technologies based upon laboratory results. Farming Systems Research (FSR) provides methodologies and concepts that bridge the gap between formal commodity research (including crop residues and by-products) and field application. This paper reports the experiences of a project in India that changed the emphasis from a commodity research approach on improved crop residue feeding to a system approach by using three types of FSR. The paper first reviews the achievements of on-station research on feeding systems for crop residues in terms of treatments (biological, chemical, physical) and in terms of breeding and managing cereal crops for more and better straw. Next, it discusses definitions and problems of FSR as encountered in the project's reorientation of livestock research and development programmes. Finally it summarizes the overall results of the three FSR approaches used in the project.

The extent of natural cross-fertilization in sesame was studied in two varieties, with contrasting flower colour, planted at two locations; in alternate rows or alternate holes; in adjacent or non-contiguous plots; and at 6 different spacings. The average out-crossing for the different treatments ranged between 3.1 and 6.7 per cent. The non-contiguous plots showed a higher degree of out-crossing than adjacent plots, in which there was a decrease in the extent of cross-pollination with increase in the distance between the dominant and the recessive parents. Alternate holes gave a higher percentage than alternate rows.

Two pigeonpea (Cajanus cajan) cultivars GT-100 (determinate type) and BDN-2 (indeterminate type) were planted on three sowing dates (30 June, 20 July and 9 August) in 1993 and 1994. Pigeonpea sown on the earliest date attained the highest leaf area index (LAI), absorbed the largest amount of photosynthetically active radiation (PAR) and produced the highest total dry matter (DM). The differences in biomass and seed yield among sowing dates were largely ascribed to totals of PAR absorbed and dry matter produced, especially in the reproductive phase. The high LAI persistence and PAR interception, coinciding with the podding phase, appeared to be mainly responsible for the increased yield in early sowings. Radiation use efficiency decreased as sowing was delayed, but did not have much effect on DM accumulation in various phases nor on final yields. Although the extinction coefficient was not influenced by sowing dates, it was inversely related to leaf area index in both cultivars. Between the cultivars, the differences in biomass reflected the differences in PAR absorbed and DM accumulation, depending upon leaf area development and growth duration. The cultivar GT-100 had a higher seed yield and harvest index than BDN-2 due to more of the DM produced being partitioned into pods during the reproductive phase on account of its determinate growth habit. Early sowings of determinate cultivars could maximize both vegetative and reproductive growth, capture more light and produce more seed yields under rainfed conditions.

Wheat yield was increased significantly when grown after sorghum intercropped with cowpeas (both for fodder and grain) or with groundnut compared with sole sorghum in the previous season. The nitrogen requirement for the target wheat yield of 4.0 t ha−1 was 108 kg ha−1 after sole sorghum and this was reduced by 87, 61, 83 and 38 kg ha−1 after intercrops of sorghum with fodder and grain cowpeas, groundnut and greengram, respectively. The different levels of nitrogen applied to the sorghum-legume intercropping systems also allowed savings of between 18 and 55 kg ha−1 of fertilizer nitrogen on wheat in the following season.

Nitrogen (N) nutrition is a key factor for vegetable growth and yield. However, different rates of nitrogen fertilization may trigger different responses to vegetables. A survey was conducted to investigate the effect of soil fertility management practices on nitrate concentration in vegetables. The survey results were used to plan experiments on the effect of chicken and cattle manures on nitrate levels in Chinese cabbage (Brassica rapa) and amaranthus (Amaranthus cruentus) grown in Tanzania and the patterns of mineral nitrogen in soils under open field conditions. Chicken or cattle manure at 200, 300 kg N ha−1 and 170 250 kg N ha−1 for Chinese cabbage and amaranthus respectively, and control were compared in a randomized complete block design. We observed a higher nitrate content in fertilized Chinese cabbage at day 30 than at day 44 after sowing, ranging from 3243 to 4993 mg kg−1 fresh matter regardless of the N source and rates. Only application of manures at high levels (250 kg N ha−1) induced significantly (p < 0.05) higher nitrate contents in amaranthus at day 28 after sowing, although there was a clear indication of nitrate accumulation even at 170 kg N ha−1 application. Soil NH4+-N + NO3−-N in both Chinese cabbage and amaranthus plots were increased with increasing N application rates and differences between control and amended soils were significant (p < 0.01). There was a positive relationship between NO3− concentration in vegetables and NO3−-N in the rooted top soil layer (0–15 cm). However, higher NH4+ concentrations depressed NO3− build up in crops and a significant negative relationship between soil (NH4+-N)/(NO3−-N) ratio and crop NO3− content was found. It is concluded that low manure application rates result in similar yields to high rates but reduces nitrate accumulation in vegetables and excess mineral nitrogen in soils.

In order to ensure sustainability of maize production in short-season environments of Nigeria, the Sudan savanna taskforce of Kano–Katsina–Maradi (KKM) Pilot Learning Site promoted short-season maize varieties in 2008 via Innovation Platforms (IPs). In the light of the promoted varieties, we evaluated the adoption and net benefits (productivity and income) of the maize varieties. We used cross-sectional household data elicited from 600 sampled households, double-hurdle model and propensity score matching. There was a remarkable increase in the adoption of short-season maize varieties in 2014 compared to what was obtained in a baseline conducted in 2008. Our empirical findings revealed that the adoption of the short-season maize varieties promoted through the IPs had significant productivity and income increasing effects. This implies that policy interventions to ensure sustainable maize intensification in the face of environmental limitations, such as early and late season drought, should intensify the promotion of short-season varieties in Sudan savannas. This will require well-concerted agricultural extension that can leverage IPs in view of its potentials.

Biofortified staple crops, amongst them cassava, are being developed to reduce problems of micronutrient malnutrition. In 2006 new cassava varieties with increased levels of provitamin A were released. For the purpose of enhancing adoption of the new cassava varieties, two strategies were used: (1) a participatory research approach and (2) public awareness raising activities. This paper attempts to evaluate the results of these two diffusion strategies. Within the first strategy, the factors found to enhance adoption rates were: awareness of the new varieties' advantages, public entities as the main information sources and involvement in participatory research. Within the second strategy, trends were found between adoption rates and producer characteristics including: ownership of land, middle-level income, advanced education level and use of information media, namely the Internet. In both strategies, a lack of seeds was one of the main factors limiting the adoption process.

The effects of temperature (13–20 °C) and potential soil water deficit (0–350 mm on the leaf appearance rates of six contrasting clones of tea (Camellia sinensis) were studied over twenty-five months to provide guidance to tea growers in southern Tanzania on the choice of harvest intervals. Within the fully irrigated treatments (potential soil water deficit <65 mm) the mean time period between a shoot unfurling its second and third true leaf (a phyllochron) ranged from 5.8–7.9 d during the warm–wet season to 11–19 d during the cool-dry season. Between 61 and 79% of the weekly variation in the mean leaf appearance rate (1/phyllochron) for each clone could be explained by an asymptotic relation with the mean air temperature. Building on research in India which has suggested that appropriate harvest intervals for tea can be derived from measurements of leaf appearance rates, a simple procedure is described for determining harvest intervals from the daily mean air temperature. Corrections to account for the effects of drought and clonal differences in responses to temperature are also explained.

In Mozambique the sweet potato (Ipomoea batatas) is often grown as both a leafy vegetable, the terminal shoots or vines being progressively harvested during the season, and as a root crop. This paper reports the results of experiments designed to evaluate the effects of drought and vine harvesting frequency on the productivity of both yield components (cv. TIS 2534). Experiments were conducted during the rainy and dry seasons, with supplementary irrigation treatments superimposed. As the frequency of vine harvesting (equivalent to the number of harvests) increased, the total fresh weight of vines increased. There was a corresponding reduction in the yield of storage roots, however, particularly under well-watered conditions. As a result, the total harvested yield (vines plus roots) was remarkably stable in both wet and dry seasons (43–45 t ha−1 fresh weight). The cumulative dry weight of harvested vines increased with the number of harvests at constant rates, depending on water availability (from +150 to +250 when rain-fed, up to +340 to +440 kg ha−1 harvest−1 when irrigated). The corresponding rates of reduction in storage root yields varied from −3 to −130 (rain-fed) down to 310 to 400 kg ha−1 harvest−1 (irrigated). Total dry weight yields under well-watered conditions were constant at about 11 to 13 t ha−1, or double this on an annual basis. Irrigation water-use efficiencies (by dry weight of harvested crop) were generally higher in the dry season than in the rains. For vine production they increased with the number of harvests from 1.6 to 3.5 (rains) up to 0.9 to 6.7 kg ha−1 mm−1 (dry season). The corresponding values for root production were 7.5 to 13.1 (rains) and 12.2 to 19.1 kg ha−1 mm−1 (dry season). For the combined dry weight yields the water-use efficiencies were, with one exception, independent of harvesting frequency at 11.2 (rains) and 19.0 kg ha−1 mm−1 (dry season). Irrigated plants harvested at weekly intervals yielded vine dry weights of about 0.5–0.6 t ha−1 week−1. Compensatory vine growth (reported elsewhere) was observed in previously droughted plants following a rainfall event. The practical implications of these results are discussed. Future papers describe in more detail the physiological aspects of the observed yield responses.

Weed management is the major challenge to the success of boro rice (rice grown during Dec–Jan to May–Jun, also known as summer rice) in Southern Asia. Herbicide seems to be a cost effective and strategic tool from an agronomic view point to control weeds; however, herbicide application can potentially interfere with soil enzyme activity and microbial biomass carbon (MBC). A field study was conducted in 2012/13 and 2013/14 to evaluate the performance of sole and combined application of different pre-emergence herbicides in comparison to manual weeding in boro rice. Lowest weed density, biomass and highest weed control efficiency (~83%) were recorded with the pyrazosulfuron ethyl, causing higher grain yield (6.7 Mg ha−1 in 2012/13 and 4.5 Mg ha−1 in 2013/14) than treatments with chlorimuron + metsulfuron-methyl, bensulfuron methyl + pretilachlor, butachlor fb 2,4D, butachlor and cono-weeder. Among, the herbicidal treatments butachlor caused lower grain yield and higher weed density and biomass when compared to the others. Although grain yield was highest in weed-free treatments but net returns and (B:C) benefit cost ratio was highest for pyrazosulfuron ethyl due to high cost of hand weeding. After 15 days of herbicide application, lowest microbial biomass carbon was recorded with bensulfuron methyl + pretilachlor, whereas lower values of dehydrogenase and fluorescein diacetate activities were observed with the application of chlorimuron + metsulfuron-methyl at 15 days after herbicide application. Our results suggest that pyrazosulfuron ethyl is one broad-spectrum and economically effective herbicide for controlling weeds as an alternative to labour consuming hand weeding in boro rice cultivation.

Studies were carried out at three locations in Ghana to investigate the effects of Glyricidia maculata shade intensity and of the spacing of coffee on the growth and yield of improved robusta coffee. The three locations selected fall within ecological zones which could be described as suitable, moderately and marginally suitable in terms of rainfall availability and soil conditions.

The experimental design was a split plot with shade as the main plot and coffee spacing as the sub-plot. The four levels of shade were: no shade, and Glyricidia maculata at densities of 70, 90 and 185 per ha corresponding to sparse, moderate and heavy shade conditions. The coffee spacings were 3 m×2 m, 3 m×2.2 m, 3.5 m×2 m and 3.5 m×2.5 m giving plant populations of 1670, 1520, 1430 and 1140 per hectare, respectively.

There were no effects of shade or spacing on coffee seedling growth at all locations during establishment. Sparse shade gave higher yields in the suitable areas. Moderate shade was required for the moderately and marginally suitable areas. In general, closely spaced coffee gave higher yields than the widely spaced coffee at the suitable and moderately suitable areas whilst there was virtually no response to coffee spacing in the marginally suitable area. There were no interaction effects of shade and spacing on coffee growth or yield. Biennial alternation of coffee-bearing associated with seedling materials was observed in this study.

Annual applications of calcium, potassium and nitrogen (as urea) over three years caused significant differences in soil exchangeable cation ratios and in the yields of subsequent groundnut and maize crops. High rates of potassium and nitrogen, combined with low rates of calcium, lowered groundnut yields, and high rates of potassium, enhanced by ploughing in crop-residue ash, seriously reduced the exchangeable Mg: K cation ratio and maize magnesium status. Maize yields were significantly negatively correlated with soil potassium status. The balance between exchangeable cations in these soils is very easily upset by injudicious combinations of fertilizers and management practices.

Chemical weed control in six root crops and fourteen vegetable crops, commonly grown in the tropics, is reviewed.