Adaptation of extra-short-duration pigeonpea in the short rainy season of a tropical bimodal rainfall environment

The adaptation of extra-short-duration (ESD) and short-duration (SD) pigeonpea (Cajanus cajan) genotypes to the short rainy season (late March to late May; yala) was studied in Sri Lanka in 1995 and 1996. Eight ESD and two SD genotypes were sown on two dates in April and May, with and without supplementary irrigation. In addition, pigeonpea ESD genotype ICPL 88039, and SD genotype ICPL 86012, sesame (Sesamum indicum cv. M.I.3), blackgram (Vigna mungo cv. M.I.1) were compared under rainfed zero-tillage conditions after a rice crop at two locations in 1996. Grain yields of the pigeonpea genotypes under rainfed conditions ranged from 0.07 to 0.47 t ha(-1) in the early sowings and 0.09 to 0.42 t ha(-1) in the late sowings. The irrigated yields reached 1.7 t ha(-1) in early sowing and 1.3 t ha(-1) in the late sowings. Irrigation differentially influenced the performance of pigeonpea genotypes in both the sowings in 1996. Analysis of pooled data showed highly significant genotype x environment (year-sowing-irrigation combination) interactions. The interaction pattern among genotypes was associated with differences in the length of the reproductive period and the partitioning coefficient of genotypes. ICPL 88039, with the shortest reproductive period and one of the best in partitioning efficiency, recorded maximum mean yield. As a rainfed post-rice crop in farmers' fields, ICPL 88039 yielded 0.4-3-1.4 t ha(-1) which exceeded yields of SD pigeonpea (0.02-0.88 t ha(-1)), blackgram (0.03-1.00 t ha(-1)) and sesame (0-0.09 t ha(-1)). The results suggest scope for introducing ESD genotypes as a sole crop in the yala season in Sri Lanka since genotypes with short reproductive periods and high partitioning efficiencies are likely to have better adaptation to this season.