Minor Season Research Articles

Effects of Planting Date and Mulching on Cowpea in Sierra Leone

SUMMARYThe effects of date of planting and soil mulching on cowpea growth and yield were investigated for three years during the middle part of the minor season in Sierra Leone. Mulching at 8 tons/ha conserved more soil moisture than other mulch rates, with greatest difference in the top 15 cm of soil, especially during drier periods. Plant height, pod number and seed yield of cowpea planted in September were significantly greater than from other planting dates whether mulch was applied or not. The beneficial effects of mulching at 8 tons/ha on cowpea growth and yield were more dramatic when the crop received an average weekly rainfall of 100 mm before 50% flowering.

Time of Planting, Rainfall and Soil Moisture Effects on Cowpea in Sierra Leone

SUMMARYAn experiment was conducted during the minor season in Sierra Leone to determine the optimum planting date for a photo-insensitive cowpea cultivar and study the relations between total rainfall and soil moisture available at different growth stages. Cowpeas planted in early September produced the tallest plants and higher grain yields than from other planting dates, since they benefited from 90% of the season's rainfall and made use of stored soil moisture. Average weekly rainfall or soil moisture in the top 15 cm of soil, recorded from planting to 50% flowering, can be used to predict cowpea grain yield.

Phosphorus Response of Maize Grown on Alfisols of Southern Nigeria1

AbstractPhosphorus plays an important role for food crop production in the forest zone of tropical Africa but very little information is available on the phosphate requirement for maize production there. Field trials were, therefore, conducted with maize (Zea mays L.) at two locations on Alfisols in southern Nigeria to investigate the P response and the residual effect of applied P. The experimental sites were recently cleared from fallow and the vegetation was removed after land clearing.On the Egbeda soil (Oxic Paleustalf), which is derived from basement complex rocks, five seasons of maize croppings were done from 1971 to 1973 using a split‐plot design with three replications. Four periods of fresh P applications (major and minor seasons 1971 and major and minor seasons 1972), formed the main plots and each of these fresh P applications consisted of five P rates (0, 26, 52, 78 and 104 kg P/ha) which made up the sub‐plots. Maize culture T2A ✕ TZB was planted at a spacing of 75 ✕ 25 cm (53,300 plants/ha). The minor season maize received supplementary irrigation. On the Alagba soil (Oxic paleustalf) which is derived from sedimentary rocks, five P rates (0, 20, 40, 80, and 160 kg P/ha) were compared using a randomized complete block design with four replications. Phosphate was broadcasted as single superphosphate and incorporated in the soil to the various treatments. The residual effects of applied P were followed up at both locations. With removal of fallow vegetation following land clearing, significant responses to P applications were observed at both locations. The P requirement for obtaining significant yield increases was not very high, ranging from 26 to 52 kg P/ha depending on season and location.Higher yield response to P was observed during the main season (April to July) than during the minor season (August to November) planting. At both locations significant residual effects of applied P was observed on maize yield and Bray P‐1 soil test levels. On the Egbeda soil it was possible to build up and maintain adequate amounts of extractable P for two to three maize crops with one addition between 52 to 104 kg P/ha.Good relationship was observed between maize grain yield and Bray P‐1 test values on the Egbeda soil. The critical Bray P‐1 test values was estimated to be about 14 ppm P. Results of incubation studies showed that under laboratory conditions 2.5 to 3 ppm of fertilizer P was required to increase the Bray P‐1 test level by 1 ppm for the Egbeda and Alagba soils respectively. Under field conditions for the Egbeda soil the P rate required was estimated to be 3.5 ppm P.The critical P in the ear leaf was estimated at 0.3% P. High rate of P application was shown to depress the Zn status in the ear leaf.

Timing the Application of N to Maize in Sierra Leone

SUMMARYTwo experiments were conducted on timing the application of N to maize on Njala upland soils in Sierra Leone. Application of all the N (urea) at planting or thinning gave lower leaf N values and relatively poor yields compared to split applications. Lower grain yields in the minor season might have been due to poor and inadequate rainfall. Basal application of SCU does not seem to release enough N for maximum grain yield of maize. Total N (urea) in the major and minor seasons may be phased in two splits, viz. ½ N 30 DAP + ½ N 50 DAP or ⅓ N at planting + ⅔ N 25 DAP, respectively.

Seasonal reproductive periodicity in the male Australian Brush‐tailed possum (Trichosurus vulpecula)

The reproduction of the possum, Trichosurus vulpecula (Kerr), was investigated on Banks Peninsula, Canterbury, from 1963 to 1965. The majority of births occur in the autumn, but there is a minor breeding season in the spring. After undergoing an anoestrous period during the summer most females enter oestrus around April. A small proportion of females give birth to a second young during September or October. Reproductive periodicity was also found to occur in the male possum. Although spermatogenesis continues throughout the year in the sexually mature animal there is a marked change in the size of the prostatic urethra at particular periods of the year which correspond to those in which the majority of females are undergoing oestrus. The mean weight of the prostate shows a sixfold increase during the autumn. However only very small changes take place in the size of the testis and epididymis. Changes in size and activity of the prostate correspond with marked changes in the interstitial tissue of the testis. Leydig cells, responsible for the secretion of testosterone, show a great increase in number in animals in which the prostate is enlarged. Associated with the growth of the prostate are changes in the behaviour of the possum. The body weight and fat deposits of the male possum drop markedly at the time of the autumn breeding season.

Amazon Cacao (Theobroma cacao L.) Shade and Manurial Experiment (K2‐01) at the Cocoa Research Institute of Ghana. I. First Five Years1

AbstractThe experimental layout, initial crop husbandry, preliminary girth measurements and yield results before and after the imposition of 2 years' shade and fertilizer treatments on the Amazon cacao Shade and Manurial Experiment (K2‐01) at Tafo are reported.In assessing the uniformity of the 4‐year‐old cacao stand analyses of data on girth measurements gave C.V. of 10.26% and 12.86% for subplot and main plots, respectively. These are remarkably lower and highly satisfactory compared with the C.V. of 57.75% for the corresponding yield.Statistical evaluation of variations between NPK fertilizer, block, cropping seasons, and shade effect is reported. The significant slope effect during the minor crop season was interpreted to be only a seasonal reflection of the probable variation in the available soil moisture. The shade effect of this experiment is compared with a similar and older experiment (Kl) at Tafo. The significant shade effect during the 1964/65 season in both cases varies with time of the year irrespective of the different shade trees.Shade, K, and PK fertilizer effects are highly significant with the dtshaded cacao yielding almost twice as the plots under heavy shade whilst the fertilizer is about 10% greater. “No shade” with PK treatment has the uniformly highest yield followed by the “medium shade” with PK and the least being “heavy shade” with PK fertilizer. Shade effect is well marked during the main cropping season while that of K is pronounced without overhead shade.There is a suggestion of rapid depletion of exchangeable K after 7 years of continuous cropping. The Amazon cacao on the WACRI series does not respond to the NPK fertilizer until it is over 5 years old.