Influence of sowing date on pod yield of yard long bean varieties

Abstract

A field experiment was conducted at the Instructional Farm, College of Agriculture, Vellayani, Kerala, from October 2024 to May 2025 to determine the optimum sowing date and suitable variety for maximizing yield of yard long bean. The study evaluated five sowing dates viz., 01 October 2024, 01 November 2024, 01 December 2024, 01 January 2025, and 01 February 2025, and three varieties viz., Vellayani Jyothika, Githika and KAU Deepika, in a split-plot design. Results revealed that sowing date and varietal choice exert a significant and interactive influence on crop duration, growing degree days (GDD), leaf area index (LAI), and yield performance of yard long bean. Among the five sowing dates, February provided the most favourable thermal and environmental conditions, resulting in superior growth and yield attributes. February sowing recorded the highest LAI (0.86), dry matter accumulation (190 g plant-1), pod weight (36 g), and pod yield (2003 g plant-1). In contrast, December sowing resulted in the lowest performance, reflected in lowest pod yield per plant (974 g plant -1), and lowest GDD accumulation from first harvest to final harvest (359 °C·days). Among the varieties, Githika was the most productive, recording the highest values for GDD from first harvest to final harvest (513 °C·days), LAI (0.83), dry matter (185 g plant-1), pods per plant (56) and pod yield (1587 g plant-1). The Githika × February interaction exhibited superior performance, characterised by maximum GDD from first harvest to final harvest (693 °C·days), dry matter (195 g plant-1), pods per plant (66) and pod yield (2329 g plant-1), confirming its thermal responsiveness. Correlation analysis further revealed that pod yield had strong positive correlation with GDD from first harvest to final harvest (r = 0.81) and LAI (r = 0.85) and moderate positive associations with dry matter (r = 0.59), pod weight (r = 0.63), number of pods per plant (r = 0.68), and LAI (r = 0.88). These results underscore the central role of canopy development, biomass accumulation, and assimilate partitioning in yield expression. The study concluded that sowing yard long bean, particularly the variety Githika during February provides the most favourable thermal environment, thereby maximizing vegetative growth, higher biomass accumulation, and improved pod yield under the agroclimatic conditions in Southern Laterites of Kerala.