A late-maturing, high-yielding maize released for the Burundi highlands was rejected by subsistence farmers. Analysis of this variety in terms of the local cropping system shows that it offers no advantage over earlier maturing varieties when whole-system biological and economic yield and Land Equivalent Ratios are examined, while farmer risk is apparently substantially increased. The value of incorporating a ‘farming systems’ approach into national commodity research programmes in developing countries is demonstrated.

In monsoon climates, the mean daytime saturation vapour pressure deficit (D), measured at screen height, decreases from a maximum of 3–4 kPa attained several months before rain arrives to a minimum of 0.5–1 kPa in the month of highest rainfall. Climatic records from India and West Africa were analysed to give the relation between D and precipitation (P mm month−1) as:

where n ranged from 0.5 to 0.9 between stations.

The dependence of dry matter production on D and therefore on P is evaluated when growth is restricted by rain and when this restriction is removed by irrigation. In the first case, the decrease in demand for water associated with a decrease in D is comparable in importance with the increase of water supply (P). The analysis has implications for the marginal response of crops to supplemental irrigation and for the interpretation of experiments with a line-source or rain-shelter.

Experiments comparing the effects of different legume intercrops on available soil nitrogen, bacterial activity and the yield of maize over two years showed that soyabean and blackgram were more suitable for this purpose than groundnut, substantially increasing NO3 and NH4 concentrations and populations of active bacteria in the maize rhizosphere. This increased maize yield by 15–20% and grain protein content by 20%.

Mixtures of legumes and cereals in various proportions (seed ratios) were evaluated in Northern Syria for forage production and quality and for yield of barley grain in the following year. Both a vetch-cereal and pea-cereal mix were tested in proportions of 0:100, 33:66, 50:50, 66:33 and 100:0. The study was carried out between 1982 and 1985, covering two seasons for forage production and two for grain production. Dry matter yields of the mixtures exceeded the yield of either one or both components of the mixture grown as pure stands, depending on the rainfall. The maximum overall yield and quality of forage was recorded for the 66:33 legume-cereal combination. The greatest benefit to subsequent barley grain yield was realized when the legume was grown in a pure stand or formed a high proportion (66:33) of the mixture. Herbage quality was better in forages containing vetch than in those containing pea.

The calibrating efficiency of the pre-experimental yield of coconuts was examined using ten years data from a calibration experiment. On the basis of a fully randomized design it was found that the two-year pooled pre-experimental yield on four-tree plots produces consistent calibration and reduces the experimental error mean square by about 73%. This brings down the mean coefficient of variation to 9.7% from its pre-calibration levels of 36 on one-tree plots and 18 on four-tree plots.

A grazing management study involving the new white clover cultivar Osceola grown in association with Bahiagrass cv. Pensacola was conducted on wet and dry sites with and without pesticide/herbicide treatment. A combination of heavy grazing pressure and a short deferment period before grazing during the summer and autumn resulted in the largest soil seed reserves and seedling recruitment by the white clover component. However, maximum survival of plants was recorded from a combination of a short deferment period and moderate grazing pressure.

A slight increase in plant survival and seedling recruitment was shown on the wet site. Survival potential was least in pasture treated with pesticide and herbicide. Heavy grazing pressure and short deferment periods appear essential for the survival of the clover component. Annual seedling recruitment from soil seed reserves was the primary mechanism of white clover survival from spring to spring in pasture associations based on tropical bahiagrass.

If corn-soyabean intercrops are to replace corn grown alone, maintenance of yield and improvements in forage quality are important. Total yields and inter-crop competition in corn-soyabean intercropping experiments have been discussed previously (Putnam et al., 1985). In Part II yield composition, components and protein content are presented for intercrops of varying planting patterns and corn densities. Most intercrop patterns produced more forage than sole crops compared at the same yield ratio of corn-soyabean as in the intercrop harvested mixture. At high plant density ear yields in the intercrop were increased while in sole crops they were reduced or unaffected. The increase was a result of an increased number of ears, weight per ear and kernel, and number of kernels per row in the intercrops. Increases in crude protein content over sole crop corn of 11–51% were shown for the various intercrop treatments. Crude protein yields in the intercrops were greater than either sole crop in 1981 and greater than corn and similar to soyabean in 1982, and greater than the crude protein yields expected from an equal planted area of sole crop corn and soyabean in both years. Intercrop forage quality was improved over sole corn both by the addition of protein from soyabean pods and an increased ear: stover ratio of the intercropped corn.

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.

Reduction of leaf area in sorghum without tillers (uniculm sorghum) might result in conservation of water at early stages of growth and hence in stability of grain yield under dry conditions. In two experiments in south-east Queensland, Australia, tillers were removed by hand to examine the growth of uniculm sorghum. Tiller removal promoted root development at the flag leaf stage but significantly reduced shoot dry matter and lowered grain yield by about 20% in a wet season. The saving in soil water as a result of tiller removal was relatively small but statistically significant.

The ureides allantoic acid and allantoin form a bright pink compound with acidic p-dimethylamino cinnamaldehyde. It is possible to estimate the ureide content of a soyabean petiole segment by crushing it on filter paper and developing the colour with this reagent. There is a strong correlation between the spot test and estimates from colorimetric determination of ureides. In field grown soyabeans, there was a positive correlation between the petiole ureide content during pod fill and the integrated seasonal acetylene reduction activity. The spot test can be used to identify plants with low nitrogen fixation activity.

Increased labour costs and area under irrigation, the development of modern early-maturing varieties and improved fertilizer and weed management techniques have encouraged many farmers in the Philippines, Malaysia and Thailand to switch from transplanted to direct-seeded flooded rice culture. This paper summarizes the development and spread of the technology for direct-seeded flooded rice in southeast Asia and the contribution made by research at IRRI and by national programmes. It covers research on crop establishment, varietal requirements, fertilizer management, weed control and economics and examines the advantages and disadvantages of direct-seeding compared with transplanting.

Five varieties of French bean of contrasting growth habit were grown at a range of plant densities. Most varieties yielded best at 30 plants m−2, but the bush type variety Contender yielded best at 50 plants m−5. The best yield was obtained from the semi-spreading variety Rufus.