Influence of sowing date on the growth and yield of bambara groundnut landraces in Tanzania

Sequential sowings were carried out at Dodoma, Tanzania, to examine the eff ect of changing climatic parameters on the growth and yield of bambara grou ndnut ( Vigna subterranea). Sowings cook place on 4 January. 4 February and 4 March 1994; 4 and 24 January, and 13 February 1995; 4 and 21 January, an d 7 February 1996. Rainfall during the crop life cycle varied from 163 re 6 11 mm, mean photoperiod From 11.82 to 12.09 h d(-1) and mean temperature fr om 22.6 to 24.4 degrees C. In 1994. the highest pod yields were achieved at the earliest sowing dare, with a maximum of 2.87 and 1.42 t ha(-1) for the red- and cream-seeded landraces, representing pod harvest indices of 0.56 and 0.34 respectively. A 30-d delay in sowing caused >60% reduction in pod yield, and a further 30-d delay resulted in no pods at all. Similarly, in 1 995 successive delays in solving caused dramatic yield declines, and the ma ximum yield was much lower, at 0.44 r ha(-1). In 1996 there was no signific ant difference in pod yields between the two early sowing dates for the red -seeded landrace and yields were again lower than in 1994 with a maximum of 1.02 t ha(-1). Differences in dry matter production between sowings and ye ars were attributed mainly to differences in the amount and distribution of rainfall and to declining temperatures towards the end of the season; howe ver, partitioning to pods was remarkably consistent across sowings.