Effects of seasonal variation in temperature and cultivar on yield and yield determination of irrigated groundnut (Arachis hypogaea) during the dry season in the Sahel of West Africa

In the Sudano-Sahelian zone of West Africa there is potential for groundnut (Arachis hypogaea L.) to be grown as a dry-season crop where irrigation is available. However, there are substantial variations in the temperatures d uring the post-rainy season that can be expected to influence growth and yi eld. An experiment at the ICRISAT Sahelian Centre was done in order to stud y the effect of sowing date on phenology, yield and the processes of yield determination for four groundnut cultivars under irrigation in the dry seas ons of 1990/91 and 1991/92. Starting on 15 November, eight sowing dates at 2-weekly intervals were tested. Sowing date significantly affected phenolog y (time to emergence, flowering and maturity) with groundnut sown in Novemb er/December taking the longest time to reach these phenological stages. Nov ember and December sowings gave the highest pod yield within each year, des pite the lowest crop growth rates (B), and yield declined progressively as sowing occurred later (50 % decrease by March) despite increasing B. The ob served responses appear to have been due to the effect of temperature diffe rences during the pod-filling phase on partitioning. Partitioning (p) to po ds was optimized at c. 30 C, with some indication of cultivar differences i n partitioning response to temperature. Across all the environments, cultiv ars displayed substantial differences in yield stability. When sown late, y ields were low and lines with high partitioning were the best. When sown ea rly in the post-rainy season, cultivars with a high B value were the better choices. Plant habit differences and B suggest that radiation interception was a limitation to yield, particularly when the crops were sown in the co ol months of the year. However, haulm yield and crop growth rates were not consistently affected by sowing date across the years, and cultivars demons trated different degrees of stability for B. It is concluded that where pod has a price advantage over fodder, irrigated groundnut for the dry season should be sown in November to allow the crop to develop under the relativel y cool temperatures that maximize pod yield. Further agronomic research is suggested to maximize B for individual cultivars for given sowing dates.