The adaptation of cold-tolerant sorghum and maize to different environments in the highlands of Kenya.

Abstract

2 new introductions of high alt. sorghum, one a grain type and the other a forage type and 2 maize cv. were tested in a number of trials during 1974-7 in the highlands of Kenya. Yield data were regressed on alt., rainfall and some data on temp. Alt. had no significant effect on either grain or forage yield of any crop over the range tested (1525-2593 m). Yields were positively correlated with rainfall and negatively with temp. The grain sorghum benefited less from increased rainfall and also suffered less from reduced rainfall than any other entry. There were indications that the same grain type sorghum was more sensitive to temp. than any other entry. The interaction between genotypes and environments was considered more important than the av. crop yield. For an accurate estimate of this interaction the yield stability analysis, whereby yields were regressed on the environmental index, proved essential. Although rainfall was the most important factor affecting yields, it only explained c. 50% of the yield differences, whereas the index accounted for more than or equal to 90% of the yield differences. The grain sorghum was the highest yielding grain crop at low and medium rainfall levels, but this was only partly due to its superior water-use efficiency and was mainly due to a more favourable DM distribution. The forage sorghum was the highest DM yielding entry under most conditions. The maize cv. outyielded the sorghums only if growing conditions were good. Where rainfall was high (>1000 mm) DM yields of all crops were lower than where rainfall was 800-1000 mm. Sorghum yields were especially reduced at high rainfall giving the maize a distinct advantage; it was not clear whether this effect was due to rainfall or temp. differences. (Abstract retrieved from CAB Abstracts by CABI’s permission)