Refining Harvest Timing and Physiological Maturity for Optimal Seed Yield in Caribbean Stylo (Stylosanthes hamata)

Abstract

A study was carried out at the ICAR- Indian Grassland and Fodder Research Institute, SRRS, Dharwad, Karnataka, India, during the Kharif 2022-23. The aim was to standardize cutting schedules and determine the physiological maturity of Stylosanthes hamata to improve seed production. Flower phenology studies revealed that the baker method was effective for estimating pollen viability. It was noted that Stylosanthes exhibited protandry, with a total of 10 stamens, where the development of 5 long anthers preceded the remaining 5 short anthers by 1-2 days. The highest pollen viability was observed during the morning hours on the day of anthesis, reaching a maximum of 67.05%. The main flowering period for Stylosanthes was from September to December, with an additional minor blooming period observed during April-May. After anthesis, Stylosanthes flowers lasted for a maximum of 8-9 hours before wilting. The use of mulching significantly improved various of growth and flowering parameters, as well as seed yield and quality. At 60 days after sowing (DAS), initial plant height was similar for plots without mulch (M1) and those with mulch (M2) at around 30.85cm and 30.68cm respectively. However, by 90 DAS, plants in the M2 plots had significantly greater height (66.65cm) compared to those in M1. Similarly, various other parameters such as days to 50% flowering (88.35), number of branches (6.25), days to maturity (159.18), seed yield (771.98kg/ha), seed germination (35.65%), shoot length (7.30cm), root length (6.55cm), seedling vigor index (494.91), seeds on plant (5.83%), physical purity (82.33%), test weight (3.24g), and minimum seeds fallen on the ground (78.18%) were also significantly improved with mulching. These results were consistent across different stages of harvesting at 170-180 days after sowing, indicating physiological maturity. Therefore, for optimal growth, seed yield, and quality in Stylosanthes seeds, harvesting at 170-180 DAS with mulching is recommended.