The on-farm evaluation of three feeding strategies for smallholder campesino dairy herds was undertaken in the highlands of Central Mexico with cooperating farmers: traditional, alternative and intermediate feeding strategies. All three incorporated grazing of cultivated pastures, but concentrate use was 4.0 and 7.0 kg per cow per day in the rainy and dry seasons respectively for the traditional feeding strategy, 3.3 for the alternative feeding strategy in both rainy and dry seasons and 5.0 and 9.0 kg per cow per day in the rainy and dry seasons respectively for the intermediate feeding strategy. Feeding during the dry season was based on maize straw in the traditional strategy, on pasture complemented with maize silage in the alternative feeding strategy, and with some maize silage but mostly maize straw in the intermediate feeding strategy. The trial ran between 25 September 1996 and 24 September 1997, divided by season into four, thirteen-week periods. Milk yields were recorded once per week, and live weight and body-condition score, every 28 days. Three cows per strategy that completed each period were blocked according to stage of lactation and used for the statistical analysis of a split-plot design with feeding strategies as main plots and weeks as split-plots. Overall mean milk yields were 15.5±2.05, 13.4±2.43 and 12.4±2.37 kg milk per cow per day for alternative, intermediate and traditional feeding strategies respectively, with significant interactions (P<0.05) for autumn, winter and summer. The alternative feeding strategy (with over 50% less concentrate) produced milk yields 0.24 and 0.38 higher than the intermediate and traditional feeding strategies in the dry season. In the rainy season, milk yields with the alternative feeding strategy (30% less concentrates) were 0.09 and 0.16 higher than the other two strategies. Margins per day of family labour were: alternative feeding strategy US$36.48 per day, intermediate feeding strategy US$9.22 per day and the traditional feeding strategy US$9.11 per day, although in the case of the last two there were two family members in charge of the dairy herds. Results demonstrate the successful integration of grazed pasture and maize silage for the efficient production of milk, and provide evidence on the productive use of limited campesino land resources in the face of unviable economic conditions for maize grain production.

A three-year field experiment was undertaken to evaluate the effects of tillage methods on grain yield and yield components of wheat (Triticum aestivum) in continuous cropping. The experiment was conducted on a Ramjerd, fine, mixed, mesic, typic Calcixerepts soil. Wheat was sown: (1) after burning residues followed by conventional tillage, (2) after complete residue removal followed by conventional tillage, (3) after soil incorporation of residues followed by conventional tillage, (4) into untilled residues, (5) using chisel seeder after field irrigation, (6) using chisel seeder plus herbicide application, and (7) after disking. Residue burning and removal increased spikes per square metre, grain per spike, 1000-grain weight, grain yield and harvest index compared with other treatments. This was due primarily to weed interference and lack of uniform crop establishment in the presence of residues. Reduced tillage methods retained more residues on the soil surface, which provided unsuitable conditions for crop emergence and growth. The incorporation of residues led to a build up of carbon in the soil, with lower grain yields compared with residue burning and removal, but these yields were higher than those of chisel-seeded plots.

Tea (Camellia sinensis) clones (PC113 and SFS204) sensitive to very dry air and clones (PC114 and SFS150) that are tolerant, were studied at two tea estates (Tshivhase and Grenshoek) in the Northern Province of the Republic of South Africa. Among the morphological leaf traits studied, stomatal density, pore diameter and pore depth were not linked consistently to stress tolerance. Cuticle thickness was not a good indicator of stress tolerance because genetic differences between clones were confounded by the clonal response of wax production to stress. In contrast, measured leaf conductance to water vapour transport was larger and leaf water potential was lower in sensitive clones, but only with more severe atmospheric stress (Grenshoek). Also the ratio of the calculated maximum stomatal conductance in old and young leaves was higher in sensitive clones, suggesting that the loss of a larger fraction of the total stem flow by old leaves enhanced the stress experienced by the young leaves. However, this indicator was valid only under the more stressful microclimate of Grenshoek. The results indicate that even promising criteria for stress tolerance should be tested by exposure to stress during selection.

In Malawi, intensive production of maize (Zea mays) is pursued on over 60% of smallholder land, yet application of nutrients is almost nil. To improve adoption of soil productivity-enhancing technologies, two participatory methods were pursued: (i) a novel ‘mother-and-baby’ trial design and (ii) participatory action research with communities in a southern Malawi watershed. The central ‘mother trial’ was managed by researchers (replicated within a site) and systematically linked to farmer-managed ‘baby’ trials to cross-check biological performance with farmer assessment. The watershed approach involved a partnership of researchers and farmers addressing soil management. Technologies tested in both approaches integrated legumes into existing maize-based systems, sometimes in combination with inorganic fertilizers. Across methods, legume intensification increased yields by approximately 40% (net benefit increase of approximately US$50 ha−1) and fertilizer increased yields by approximately 70% compared with continuous maize grain yields of about 1100 kg ha−1. Farmer assessment prioritized technologies that included secondary benefits, such as weed suppression, grain legume yields, and low-labour-demanding fertilizer. A survey indicated that participating researchers and extension staff had reservations about the amount of time required to interact with farmers, and no clear consensus emerged regarding the best approach. There has been wider adoption of the mother-and-baby trial method by scientists in neighbouring countries, indicating the value of systematically incorporating farmers' input.

Foliar sprays of 25–100 mg L−1 dinitrophenol, sodium azide (NaN3) and thiourea solution applied to Azolla microphylla (strains 202 and 203) at seven days after inoculation significantly increased the sporulation frequency and number of micro- and mega-sporocarps per plant. Azolla biomass production was decreased by the application of NaN3 at 50–100 mg L−1 and dinitrophenol or thiourea at 75 and 100 mg L−1. Both the sporulation frequency and sporocarp number were maximal with dinitrophenol and NaN3 at 100 mg L−1 and thiourea at 75 mg L−1. At this concentration, NaN3 was more effective than dinitrophenol and thiourea in enhancing sporulation in A. microphylla (strain 203). The sporulation frequency and micro-sporocarp number were significantly higher with gibberellic acid (2.5 mg L−1) than with indole acetic acid (6 mg L−1) application, while the effects of NaN3 were comparable with those of gibberellic acid. The mega-sporocarp numbers in these treatments were comparable. The combined application of any two of the metabolic inhibitors had antagonistic effects and decreased the sporulation frequency and sporocarp number over their individual applications. Combined applications also substantially reduced the biomass production. The application of gibberellic acid or indole acetic acid along with one of the metabolic inhibitors had synergistic effects on the formation of sporocarps and significantly increased the biomass production, irrespective of the metabolic inhibitor treatment. The number of both micro- and mega-sporocarps in the gibberellic acid + NaN3 and indole acetic acid + NaN3 treatments, and micro-sporocarps in the gibberellic acid + dinitrophenol, indole acetic acid + dinitrophenol and indole acetic acid + thiourea treatments was significantly higher than when each of these chemicals was applied alone. Of the different combinations of gibberellic acid, indole acetic acid and NaN3, gibberellic acid + NaN3 recorded the highest sporulation frequency and micro-sporocarp number, and indole acetic acid + NaN3 the highest mega-sporocarp number. Application of all three chemicals together had no extra advantage.

In any experiment the land will not be completely uniform and it is helpful to have ways of allowing for the variation. Some sources, for example altitude, will be obvious; some will be permanent but less obvious, such as depth of topsoil; and some may depend upon season and so be unpredictable. Various methods of local control have been suggested. Where the experimenter has good knowledge of the land it can be divided into blocks, each as far as possible uniform within itself. Then comparisons are made within the blocks rather than within the area as a whole. Where such knowledge does not exist, it is sometimes reasonable to make an assumption about the fertility pattern and make use of that, as in a row-and-column design like a Latin square. There is also the possibility of judging the fertility pattern from the data themselves and assessing the performance of a plot by reference to that of its neighbours.

The approach will be to generate bodies of data on the computer to form realizations of diverse fertility patterns and to use all methods on all realizations, noting success and failure.

When the variation forms a trend, blocks succeed only if they are aligned along fertility contours; the other methods do not depend upon orientation. Row-and-column designs can fail badly if the rows and columns interact. Some random variation is inevitable and it makes all methods less effective, especially nearest-neighbour methods, which can fail also when there are discontinuities. Random patches of different soil types are very difficult to deal with and any method might fail.

Output:input ratios and apparent balances for nitrogen (N), phosphorus (P) and potassium (K) were measured in a rice-wheat system at Modipuram (29.4°N, 77.46°E, 237 m asl), India, under two planting densities (P1 = 200×200 mm for rice, 230 mm row spacing for wheat, and P2 = 200×100 mm for rice, 150 mm row spacing for wheat), and two levels of fertilizer NPK (100% F = recommended levels of fertilizer N, P and K for each crop, i.e. 120 kg N, 26 kg P and 33 kg K ha−1, and 150% F = 150% of the recommended levels) with and without 5 t ha−1 farmyard manure (M) to each crop. After two cycles of the rice-wheat rotation at a fixed site, N and K balances were negative for all treatments, but P balance was negative only in plots treated with P1 + 100% F treatment. The largest yield in the system, 15.7 t ha−1, was obtained in plots receiving P2 planting density with 150% F + M treatment, and the smallest (13 t ha−1) in plots of P1 planting density with 100% F treatment. In plots with the largest yield, total removal of NPK was 659 kg ha−1 (310 kg N, 62 kg P and 287 kg K ha−1), and in plots with the smallest yield, NPK removal was 411 kg ha−1 (188 kg N, 34 kg P and 189 kg K ha−1). At these nutrient uptakes, output:input ratios were 0.74 for N, 0.57 for P and 1.80 for K in plots receiving P2 + 150% F + M treatment, and 0.78 for N, 0.65 for P and 2.86 for K in plots receiving P1 + 100% F treatment.

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.