Nitrogen fertilizer requirements and potential forage yield of wheat, oats and Italian ryegrass grown under irrigation in Saudi Arabia were assessed. Mexipak wheat produced high DM yields with between 100 and 150 kg/ha N, and the mode of nitrogen application did not significantly affect DM outputs. Nitrogen at 150 kg/ha produced highest DM yields for oats, although the application of 50% of irrigation requirement as drainage water reduced yield by 8%. Italian ryegrass produced a mean yield of 14.6 t/ha in 169 days with a nitrogen application of 60 kg/ha; direct drilled on a field scale it yielded 8.76 t/DM/ha with a total application of 270 kg N/ha.

In short clonal rows of sugarcane the mean weight of adjacent rows contributed significantly to the variance of row weight, mainly because some clones could increase their cane number at the expense of slow-tillering clones. Weight per cane and sugar content were unaffected by competition. Significant correlations were found between sugar content and (a) the rate of leaf appearance, (b) the ratio of fresh weight of leaf blade to fresh weight of joint, and (c) fibre as a percentage of cane fresh weight.

An experiment is described on the establishment of cocoa on clear-felled land, using various ground covers on which 22 NP:KMg factorial treatments were later superimposed. Growth of cocoa was improved in mulched and clean-weeded plots and the unshaded trees began bearing two years after planting, which is exceptionally early for young cocoa in Ghana. In the third year responses to NP fertilizer were obtained and in the following year yields were very high, up to 2170 pounds dry cocoa per acre. This was partly responsible for K deficiency, particularly in plots without mulch and KMg, which led to declining yields especially on the NP plots. Significant increases were thence obtained from the KMg fertilized plots. Mulching at the rates used in this experiment is too expensive and uneconomic, but K fertilizer applied at rates higher than the present rate of 75 lb K2O/acre/annum may be needed on Ghanaian forest soils if they are clear-felled for growing unshaded cocoa.

The effect on cross pollination of four directions and six distances from the marker variety in Egyptian cotton was investigated. The percentage of cross pollination did not differ appreciably in the different directions but there were significant differences in cross fertilization among the six distances. A linear relation was observed between cross pollination per cent and distance up to 8.8 m. from the marker variety. Implications of these findings on various aspects of cotton breeding methodology are discussed.

Forty-six cultivars of linseed oil (Linum usitatissimum L.) were grown under wet and dry season conditions in the Sudan Savanna of Nigeria. Only during the dry season was production good and cv Dunes consistently outyielded all other cultivars in terms of seed and oil content. Trials of sowing dates gave maximum seed yield and oil content from plots sown during late October. In row spacing trials, rows 15–22 cm apart and seed rates of 58–78 kg/ha were found to be the most practicable. There was a linear relation between increasing rates of nitrogen and seed yield, maximum production being obtained at 55–88 kg N/ha, but oil content was slightly depressed at levels above 33 kg N/ha.

The best available varieties of barley, durum wheat, rapeseed, safflower and sunflower were compared for their yield of grain and oil and other traits under rainfed conditions and with supplementary irrigation in the relatively dry Mediterranean climate of Cyprus. The grain yields of the oilseed crops safflower and rapeseed when grown under conditions of plentiful rainfall or with supplementary irrigation were 3–5 t ha−l. Considering the high prices of oilseeds on the world market, the income from oil crops compares favourably with that from barley and wheat. However, under conditions of limited rainfall (300 mm) and without supplementary irrigation the yields of oilseed crops were extremely poor, at the most 0.6 t ha−1. Grain and oil yields of irrigated safflower and rapeseed were larger than those of sunflower. Among the oilseed crops, sunflower received most irrigation water and rapeseed the least. Under rainfed conditions, with precipitation less than 300 mm, cereals were the only successful crops. It is concluded that in the high rainfall areas of West Asia and North Africa, or with supplementary irrigation, including treated municipal wastewater, oilseed crops can be successfully grown.

Ten weighable containers, the same size as 4-gallon petrol tins, were located in a plot 80 metres from the leading edge of a 2-acre field of irrigated alfalfa growing under advective conditions in the Sudan. Evapo-transpiration from alfalfa growing in these containers was compared with evaporation from a series of small evaporimeters level with the top of the plants and from a standard U.S. Class A evaporation pan, and also with estimates of evaporation calculated by the Penman formula. Evaporation from the free water surfaces in evaporimeters or pan was always greater than from alfalfa in the containers when the crop was 25 cm. high or less, but lower when the crop was more than that height, whilst the figures calculated by the Penman formula were much lower than either. Cumulative water losses were also recorded from containers where the soil was kept wet or allowed to dry out, and these were compared with evaporimeter losses up to the stage where no further water was being lost from the dry containers.

The diffusion of rice varieties introduced into an area with poor production potential and problems of soil degradation was studied in a farming systems research and extension programme. Two rice varieties, BW. 272–3 and At. 85–1 were identified as appropriate for the area and efforts made to transfer the experimental results to the farmers. BW. 272–3 was widely adopted by farmers in the lower, intermediate and upper areas of the recommendation domain but adoption of At. 85–1 was confined to the intermediate and upper areas. Adoption of rice varieties was mainly governed by the characteristics that allowed a variety to perform well under adverse conditions and by the farm gate price it could command, which depended on grain pericarp colour.

Difusión de nuevas variedades de arroz

Examples are taken from three biometrical texts, two unpublished experiments and Yates (1937) to illustrate quantitatively how the lay-out of the plots can affect the estimate of error variance in field experiments and how confounding of treatment and positional effects can arise. In two examples in which the plots did not run the whole length or width of the block, the estimates of error were reduced by one half and one quarter respectively by allowing for sub-blocks within blocks or for rows and columns. In split-plot experiments where the main plots were split breadthwise, the sub-plot error was about the same size as the main-plot error or larger whereas it is expected to be at most one third that of the main plots when these are split lengthwise. Serious bias can arise in the estimate of treatment effects due to confounding with positional effects; this is illustrated.

In highlands, the increase in altitude results in a drastic decrease in temperature (T) that delays phenological development of maize, decreasing light interception during the cycle. This could be partially overcome by increasing plant density, but information is scarce for designing specific management options. The objective of this work was to describe changes in canopy development, photosynthetic performance, biomass and yield of maize grown at contrasting plant densities (5.7 plants m−2, locally used, and 8.7 plants m−2, 50% higher). Three experiments were carried out in two high-altitude environments within the Argentinean Andean region, Hornillos (HOR, 2380 masl, 2019–20 and 2020–21) and El Rosal (ERO, 3350 masl, 2019–20), and complementary data were obtained from samplings in 8 farmer’s fields (from 2400 to 3400 masl, 2022–23). In the experiments, mean T during the first 150 days of the cycle was 33% lower at ERO, which implied 39 extra days but 25% shorter thermal time to achieve silking. The higher plant density significantly increased leaf area index and light interception at ERO, whereas at HOR, this was only evident during the second season. At the leaf level, plants grown at ERO had thicker leaves with higher chlorophyll (+36%) and nitrogen (40%) content. Photosynthetic electron transport rate at full irradiance was +20% higher at ERO but significantly varied throughout the day with lowest values in the morning, which was not observed at HOR and was not related to light intensity or stomatal conductance. At HOR, the increase in plant density did not improve light interception, nor yield in 2019–20 (with average yields of 6356 kg ha−1) but it did improve both in 2020–21 when generally lower yields were attained (4821 kg ha−1). Across farmer’s fields, increasing densities consistently reduced yield per plant (r2 = 0.57***) but improved yield per area basis, which was maximised at 10 pl m−2 as a result of a steady increase in kernel number m−2 (up to 15 pl m−2). Thus, in these high-altitude environments, increasing plant density beyond recommended (6 pl m−2) is a promising approach for improving yield, with major penalties of supra-optimum densities being related to kernel weight. Further work is needed to explore the effect of different factors limiting kernel growth, over plant density responses.