Fertilizer response of cold-tolerant sorghums under semi-arid high-altitude conditions.

Abstract

5 fertilizer trials were carried out in 1974-5 at 3 different high-alt. locations in Kenya. In 3 of the 5 trials the yield response of a grain-type sorghum cv. was compared with the response of a forage-type cv. to N and P. In the other 2 trials the yield response of a grain-type sorghum to N, P, K and Mg + Zn, B and Cu was studied. Rainfall during the field period of the crop varied from 225 mm to 811 mm. There was no interaction with yr, but the responses varied greatly with trial site. Although DM yields obtained from the grain type in the driest trials were considered good (4.9 t DM/ha on 255 mm and 7.2 t DM/ha on 294 mm), no response to N or P was observed. Under wetter conditions it appeared that N increased the total DM yield of the forage-type cv. and the grain yield of the grain-type cv.; the type was accentuated. P increased the grain yield and total DM yield of the grain-type cv. Both N and P increased the CP content of the forage sorghum, but with the grain sorghum only N increased CP content whereas P decreased it. K and trace elements had a positive influence on yield in 2 experiments, but more work is needed to evaluate this effect in detail. Yield and forage quality differences resulting from different fertilizer applications were small. One possible reason for this is N-fixation in the soil, but more research is needed to substantiate this. In the trials with the lowest rainfall, the earlier maturing grain type outyielded the forage type, but if rainfall was less limited the forage type had a clear advantage over the grain type. (Abstract retrieved from CAB Abstracts by CABI’s permission)