In trials over 2 years at five locations in Northern Nigeria single inputs were removed from a package of maize practices. The improved variety was most important and increased the yield of the otherwise complete package by 86%. Early sowing and high plant population were not important in all trials. The high fertilizer treatment (125–50–50 kg NPK/ha) consistently exceeded the half rate, with a mean increase of 31%. It was suggested that, with clean weeding, priority should be given to the improved variety, high fertilizer and early sowing. High populations, involving changes to traditional techniques, may be introduced gradually.

There were significant differences in dry matter yield among five forage oat varieties tested at ten environments during 1970–75. The correlation coefficients between annual rainfall and DM yield varied with variety from 0·69 to 0·88, late varieties tending to give higher yields. Lateness, and high varietal response to annual rainfall and improved environmental conditions, can be used as selection criteria in semi-arid regions. Late varieties had higher DM and lower crude protein contents, and forage produced under lower rainfall conditions tended to have more DM and crude protein.

Agronomic techniques to even out the intra-seasonal fluctuations in yields of tea in Malawi are described, and evidence presented of their effects on the level and distribution of yield. Such treatments reduce yields per acre, but by overcoming constraints on capacity they may lead to increased yields for the estate as a whole. The full benefit of some of these practices requires the prediction of yield patterns based on current and expected weather. Several techniques can be combined to form a flexible approach adapted to each particular year, but more work is required to quantify the parameters and functional relations involved before alternative strategies can be properly compared.

Seed yield in two soyabean varieties—one tall (Improved Pelican) and one short (V/1)—was mainly determined by the total number of main stem and branch pods produced when plant population density varied from 5·4 to 16·2 plants/m2. An increasing percentage of the pods was found on the main stems of Improved Pelican as the crop stand became denser.

Average seed yields of effectively nodulated cowpea plants were 38% greater than those of non-nodulated plants when both received applied nitrogen at concentrations ranging from 60 to 240 ppm during one of three periods: emergence to first flower, first flower to mid pod-fill, or mid pod-fill to maturity. Nodulation increased seed yields by 45% when plants received a ‘basal’ level of 30 ppm N throughout growth. None of the combined nitrogen treatments could compensate non-nodulated plants for the loss of symbiotic nitrogen fixation. Non-nodulated plants relying on applied N branched less, produced fewer peduncles and set fewer pods on each peduncle than nodulated plants.

Combining ability analysis was carried out on diallel crosses of 20 yellow maize varieties in four environments. General combining ability variance (σ2g) was of greater importance than specific combining ability (σ2s) in the inheritance of all traits except grain yield and ear length, where the reverse was true. Interaction components (σ2ge, σ2se) were greater than the respective main components (σ2g, σ2s) for grain yield. The study brought out the prominent role of genotype-environmental interactions. Heritability in the broad sense was very high for all traits except grain yield and grain moisture, and narrow sense heritability was also high for all traits except grain yield and ear length.

It is suggested that quite a small computer, in association with a minimal program for the analysis of variance, can be used to calculate quantities of use to the agronomic research worker beyond what he usually obtains. For example, without further programs it is possible to calculate an analysis of covariance, in which adjustment is made for some disturbing factor. It is also possible to find how much of the error variance arises from a particular plot, and to deal with situations in which data are incomplete or the yields from two plots have become mixed.

The sulphur content in the sixth leaf from the apex of coconut palms was found to be the most sensitive index to sulphur treatments. Although the S concentration in this leaf correlated negatively with applied levels of S, the response curve was concave. Sulphur treatments increased the total yield of fruits and weight of copra, but decreased the weight of kernel per nut. The derived curve for yield versus S concentration in the tissue was C-shaped, attributed to growth dilution effects caused by enhanced initial growth following the restoration of a nutrient in minimum.

The properties are discussed of a number of relatively simple equations that describe non-linear relations of the type which frequently occur in biology. Most of the equations can be linearized by applying simple transformations (e.g. logy, log (a–y), I/y) to either y or x, or both. Some approximate methods of fitting the equations to experimental data are given, but statistical methods are not discussed in any detail.

A small bench-mounted seed thresher for vegetables has been developed for the use of plant breeders. The construction and operation of the thresher is described.

Three varieties in one cassava trial and five in another were planted in a systematic density experiment which showed that optimum plant density for root yield changes with plant age. Some varieties showed a pronounced optimum plant population, whilst others showed a flattopped response curve. Reduction in yield above the optimum is due to a reduced harvest index. Yields of over 50 t–ha were obtained with varieties that respond to close spacing.

An investigation was carried out to study the effects of boron (0, 1, 2 and 3 kg/ha) and nitrogen (0, 50, 100 and 200 kg/ha) on the growth and yield of radish cv Pusa Rashmi. Various growth characters such as number, fresh weight and dry matter content of leaves, and length, girth, fresh weight and dry matter content of roots increased with increase in boron and nitrogen levels, the highest application of both nutrients giving the best results. Treatment combinations showed significant effects on fresh weight of leaves and roots, with the best results from 3 kg boron + 200 kg of nitrogen/ha.