Although viewed as important for on-farm adaptive research, farmer-participation has often been superficial and has not led to meaningful incorporation of farmer perspectives. This paper describes the use of a method involving the understanding of farmers' perceptions in determining priorities for research which integrates the different concerns and contributions of farmers and scientists with the transfer of technology from farmer to farmer.

Farming systems in the wetter tropics may be divided into three simplified models: the irrigated paddy-rice multistorey homestead garden complex of Asia, the tree and cash crop plantations of Latin America, and the mixed root crop-bush fallow systems of Africa. In upland ecosystems, sustainable farming systems development rests on a delicate balance between conservation and utilization. To meet the basic food and nutritional needs of the indigenous population, there is great potential for the improvement and adaptation of multistorey homestead gardens and mixed systems which include trees and annual and perennial crops. The principle and practice of ‘alley cropping’ provide an ecologically sound basis for future farming systems research and development in the region.

The questions and design of pasture research in tropical Australia and the resulting technologies address problems encountered in the prevailing extensive beef-production systems. In African pastoral systems, forage resource use is more intensive and complex, and production aims are manifold. An example of applied research in central Nigeria illustrates the usefulness of certain components of Australian pasture technology but the need to adapt them, particularly with respect to pasture utilization and management, within trials deliberately designed to address the differing problems in the local pastoral system.

Farmer-managed trials with browse trees were undertaken at two locations in southeast Nigeria. The fast-growing tree species Leucaena leucocephala and Gliricidia sepium were either inter-planted with crops as alley farms or planted in pure stands as intensive feed gardens. At both locations, most of the trees established successfully under farmer management. However, the quality of establishment was uneven, and the rate of utilization generally poor, especially at one site. The limited success of the trials is traced to a number of related sociological, institutional and edaphic factors. These include poor soil fertility; the incompatibility of established cropping patterns and rotation practices with the planting of trees on farms; the division of labour and organization of decision-making within the household; and land and tree tenure rules. It is argued that farmer-managed trials are necessary to reveal the importance of sociological and institutional factors in farmers' decision making, and that such trials require a high level of farmer autonomy in their management.

Observations that are frequencies rather than measurements often call for special types of statistical analysis. This paper comments on circumstances in which methods for one type of data can sensibly be used for the other. A section on two-way contingency tables emphasizes the proper role of χ2 a test statistic but not a measure of association; it mentions the distinction between one-tail and two-tail significance tests and reminds the reader of dangers. Multiway tables bring new complications, and the problems of interactions when additional classificatory factors are explicit or hidden are discussed at some length. A brief outline attempts to show how probit, logit, and similar techniques are related to the analysis of contingency tables. Finally, three unusual examples are described as illustrations of the care that is needed to avoid jumping to conclusions on how frequency data should be analysed.

This paper concludes the series with comments on regression, covariance analysis, and correlation. The importance of choosing a regression function, whether linear or non-linear, appropriate to problem and data is emphasized and the nature of parameter estimation is outlined. The merits of transformation of variates and the importance of introducing a proper number of parameters are briefly discussed. Common misunderstandings of the meaning of ‘the regression of y on x’ for experimental data are related to the analysis of covariance.

Regression with two or more regressors increases the computations but does not alter principles. Adjustment of means by use of covariance analysis is a much under-exploited technique in its direct sense; it also offers a computationally convenient way of handling missing observations and related problems. An attempt is made to overcome the confusions of interpretation between the regression equations of y on x and of x on y. A final section warns against misuses of correlation coefficients; the opportunities for misuse are too many for brief summary, yet such coefficients can be helpful when interpreted with care.

Simple methods are proposed for measuring the relative importance of grain and fodder produced jointly from maize fields in four zones in northern Pakistan. These methods suggest that the joint production of grain and fodder from maize is important in all four zones and that fodder accounts for between one-third and one-half of the total value of the crop. The relative value of fodder production is particularly high in two of the zones (the irrigated mid-altitude Swat Valley and the rainfed low altitude Islamabad District), both characterized by a high ratio of animal numbers:maize area. The results suggest that maize research and extension recommendations that do not take into consideration the fact that farmers produce maize for fodder as well as grain will often not be accepted by farmers.

Additivity, variance homogeneity, and normality are often regarded as prerequisites for analysis of variance. Although they are desirable, their truth is never certain; they are important to probability levels in significance tests, but not to the general informativeness of the analysis. Transformation of data may improve conformity to these desiderata at the cost of producing results on a scale ill-suited to the objectives of the experiment. In this paper the generalized power transformation and the inverse sine transformation are described, and the practical problems of choosing an optimal transformation discussed. An ideal choice can seldom be based on the evidence of one experiment, and adopting the same transformation for a series of similar experiments is usually more helpful than a search for the ‘best’. Warnings are given about inappropriate guides to the choice of transformation. In some experiments, separate analyses for two or more obviously distinct sets of treatments may be more rewarding than any attempt to find a transformation that will enable all to be handled at once. When one or two treatments (or treatment combinations in a factorial experiment) show data wildly out of line with all others, consideration of reasons should precede and possibly replace any approach through transformation. A sound general principle is that data are usually most clearly interpreted on the original scale of measurement. Therefore, transformations should be avoided unless clearly necessary; by this advice, I do not imply prohibition. Finally, attention must be given to the presentation of results; the most effective presentation does not necessarily employ a transformation or other special device adopted earlier in a statistical analysis.

Laboratory experiments and field tests were used to study the effects of seven anti-microbial agents and a trace element salt mixture (TEM) on the decay of cut pieces of seed potatoes. The effect of a mixture of gibberellic acid and ethrel (GA + E), TEM, and TEM with GA + E on the sprouting behaviour and yield of tubers was also studied. All the anti-microbial agents inhibited decay, although TEM and oxine were superior to other treatments. There was an increase in crop yield when seed tubers were treated with TEM. In laboratory tests, the GA + E mixture and TEM were effective in breaking dormancy.

Trees are important sources of food in both the humid and semi-arid tropics. Some species have been exploited for centuries and are widely distributed around the world, others have been cultivated only in limited areas, while most are still essentially wild. The potential for rapid genetic improvement by clonal selection is enormous and well-proven by the recent history of some species. Trees can yield as much food per hectare as most C3 annual crops – although special problems may have to be overcome to ensure regular bearing of fruit and nut trees. Trees also offer great ecological and social benefits.

Nodulated plants of Stylosanthes hamata, S. guianensis, S. humilis, S. scabra and S. fruticosa were grown in controlled environments with varied root and shoot temperatures. Measurement of dry matter and nitrogen content suggested that shoot temperature may be more important than root temperature in controlling growth and nitrogen fixation. There were strong interactions with variety. A fall in relative growth rate with increase in shoot temperature was least for S. guianensis and greatest for S. hamata and S. scabra. The optimum root temperature for growth and nitrogen fixation was approximately 30°C. Ninety percent maximum yield was achieved between root temperatures of 15–36°C for growth and 23–34°C for nitrogen fixation but varied with variety. Nitrogen fixation was more sensitive than dry weight to root temperature. The pattern of response of percentage nitrogen and nitrogen fixation efficiency reflected those for dry weight and nitrogen yields. Shoot to root ratios decreased toward the optimum root temperature then increased at the highest temperature. The reaction of varieties to root and shoot temperatures may be an important factor in determining their suitability for new regions.

Paddy rice was grown without fertilizer after jute which had been supplied with nitrogen as neem cake coated urea (NCU), wax coated urea (WCU), ammonium sulphate or standard urea at rates of 0, 40, 80 or 120 kg N ha−1. NCU or WCU applied to jute increased the dry matter and grain yield of the rice, suggesting that enough nitrogen is left behind to grow a subsequent rice crop without further fertilizer application.

Nodulated plants of six varieties of Stylosanthes were grown at a constant temperature of 30°C for 21 days in a controlled environment and then for a further 21 days at a range of day/night root temperatures. Dry matter and nitrogen content of S. hamata cv. Verano and CPI40264A were measured after growth at day/night root temperatures of 30/30, 40/30, 50/30, 60/30 and 60/35°C. Similarly, growth and nitrogen content were measured for Verano, CPI40264A, S. gvianensis cv. Oxley and cv. Cook, S. humilis cv. Lawson and S. scabra cv. Seca after growth at root temperatures of 25/20, 25/25, 30/25, 30/30, 35/30 and 40/30°C. There were strong interactions of root temperature with variety and harvest time (31 and 42 days) but all varieties grew well even at the highest temperatures (50–60°C) provided they were supplied with nitrogen. Symbiotically dependent plants of S. hamata cv. Verano were more tolerant of high root temperatures and maintained better growth and nitrogen fixation at 40/30°C than those of CPI40264A, especially after the 31 day harvest. All six varieties responded similarly, but to differing extents, to the lower range of root temperatures. Nitrogen fixation was more severely affected than dry weight by high root temperature.

Seed yam production potential of three yam species (Dioscorea rotundata, Dioscorea alata and Dioscorea cayenensis) was assessed for two systems – the traditional method using 100 to 200 g setts, and the mini-sett technique using 25, 20, 15 and 10 g setts cut from mother tubers. The mini-sett technique required only 6–33% of the number of tubers needed for the traditional planting system, and resulted in plants superior to those produced by the traditional method in all their production attributes especially in the case of D. alata and D. rotundata.

Two bean genotypes differed in rate of root extension and elongation when grown under different soil water stresses in transparent tubes placed at an angle of 25°. Root intensity (the root length visible cm−2 of the viewing surface) gave a quick indication of the distribution of the total root length when screening cultivars for drought resistance.

Nodulated plants of three USA cultivars of lentil (Lens culinaris) were grown in controlled environment cabinets. They were given either 20 or 80 ppm inorganic nitrogen and experienced a mean temperature of 12.3° C during the vegetative period, i.e. until 73–77 days after sowing. Factorial combinations of above- (29°/11° C) and below-average (23°/8° C) day/night temperatures were then imposed, to give four mean temperatures within the range of 16.6° to 21.1° C until reproductive maturity. Post-flowering vegetative dry-matter production and seed yields were dominated by treatment effects on the initiation and growth of branches. Warmer temperatures accelerated progress towards maturity, limited branching and restricted dry-matter production; at a mean temperature of 20° C plants were almost barren. The implications of these and previous data to lentil crop production and to the use of controlled environments in lentil breeding programmes are discussed.

Field studies of the dynamics of transformation and availability of applied phosphorus in a Vertisol cropped with rainfed cotton showed that phosphorus application increased available phosphorous in the soil. However, 70–80% of the phosphorus was fixed when more than 40 kg P2O5 ha−1 was applied. Maximum uptake of phosphorus by cotton occurred during the active growth period 40 to 80 days after germination, as reflected in a steep decline in the labile pool of available phosphorus in the soil. Over 50% of the total inorganic phosphorus occurred as Ca-P, which was the major contributor to the labile pool available to the cotton crop. The maximum response of cotton in terms of both dry matter and seed cotton and the maximum uptake of nitrogen, phosphorus and potash occurred when phosphorus was applied at 40 kg P2O5 ha−1. Phosphorus application increased the length, spread, volume and weight of roots.

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.

Three irrigation regimes (250, 450, 650 mm year−1) were applied to guayule (Parthenium argentatum), a rubber-producing plant, in such a way as to provide periods of good soil water status alternating with periods of water stress. The relative water content and transpiration rate of the plants decreased only when the available soil water was depleted to about 40%. Very low values (< 30%) were measured for the relative water content. Water-stressed plants recovered as soon as irrigation was resumed. Growth and biomass accumulation, as well as the yields of rubber and resins, were directly related to the irrigation rates. The water regimes applied and the use of the drip irrigation method resulted in a relatively high water use efficiency.

Pre-flowering insect infestation of cowpea, Vigna unguiculata, was monitored in weedy and weed-free plots in 1986 and 1987 in Akure, Nigeria. Weediness generally reduced infestations of both the leafhopper, Empoasca dolichi, and the flea beatle, Ootheca mutabilis. However, seed yield was reduced in the weedy plots despite heavier pre-flowering insect populations in the plots kept weed-free.