Author(s): V. S. ANJU AND L. GIRIJADEVI

Abstract: An experiment was conducted to study the effect of sowing dates on grain yield of rice variety Prathyasa and also to work out the cumulative heat units required to attain various phenophases in direct seeded rice (Oryza sativa) in terms of growing-degree days (GDD), heliothermal units (HTU) and photothermal units (PTU). The experiment was conducted in two years during the kharif seasons of 2016 and 2017respectively and the treatments consisted of five sowing dates starting from 1st June to August 1st at fortnightly intervals.The other dates were June 15th, July 1st and July 15th respectively.The design of the experiment was Randomised Block Design (RBD) with three replications. The field experiment was conducted in the farmer's field at Kalliyoor Panchayat near College of Agriculture, Vellayani, Thiruvananthapuram, Kerala, India. The weather data recorded in the Class B observatory attached to College of Agriculture, Vellayani is used for the study. The heat units, i.e., growing-degree days (GDD), heliothermal units (HTU) and photothermal units (PTU) required for each sowing dates were computed using the formula for each phenophases based on the weather parameters recorded in the Class B agromet observatory. The heat unit efficiency (HUE) was also worked out from the dry matter production and GDD. The results revealed thatearly sowing inJune 1st resulted in more heat unit accumulation compared to late sowingin August 1stleading to higher grain yield in early sown crop.The grain yield was the highest in June 15th sowing (6443.28 kg ha-1) in first year and June 1st sowing in second year (5328.18 kg ha-1). The HUE of the crop was found high in June 15th sowing in first year and June 1st sowing in second year. Similarly the heat unit accumulation in terms of GDD, HTU, and PTU were also found higher in June 1st sowing.

Download Full Article: Click Here