Optimization of seeding rates and nitrogen scheduling in direct-seeded rice (Oryza sativa) under drought-prone environment in middle Indo-Gangetic plains

Abstract

A field experiment was conducted during the rainy (kharif) seasons of 2014 and 2015 at Patna, Bihar to optimise the seeding rates and nitrogen scheduling for direct-seeded rice (Oryza sativa L.) under the rainfed drought-prone environment. The soil of the experimental plot was loamy, low in organic carbon (0.42) and available N (149.6 kg/ha), high in available phosphorus (25.8 kg/ha), medium in available potash content (183.6 kg/ha) and slightly alkaline (pH 7.7). The treatments consisted of 3 seeding rates (S1: 20 kg/ha; S2 : 30 kg/ha; and S3 : 40 kg/ha) in main-plot and four nitrogen schedules (N1 , 1/3 N as basal and 2/3 N at maximum tillering; N2 , 1/3 N as basal and 1/3 N at maximum tillering and 1/3 N at panicle initiation; N3 , 1/2 N at first shower/enough moisture availability preferably after first weeding and 1/2 N at maximum tillering; and N4 , 1/3 N at first shower/enough moisture availability preferably after first weeding, 1/3 N at maximum tillering and 1/3 N at panicle initiation stage) in sub-plot and replicated thrice in split-plot design. The results revealed that the grain yield was significantly higher with S3 (3.2 t/ha) than that to S1 (2.4 t/ha), but statistically at par with that obtained with S2 (3.1 t/ha). Varying nitrogen schedules did not affect the grain yield markedly. Comparatively higher grain yield was recorded with N4 (3.0 t/ha) followed by N3 (2.94 t/ha) and N1 (2.87 t/ha). The gross returns (32.1 ×103 /ha), net returns (15.9 × 103 /ha) and benefit: cost ratio (1.64) were significantly higher with 40 kg/ha seed rate compared to 20 kg/ha ( 22.4 ×103/ha, 6.2 ×103/ha and 1.26 but statistically similar to 30 kg/ha ( 28.9 ×103 /ha, 13.4 ×103/ha and 1.55. The net returns were significantly higher with N4 closely followed by N3. Hence, growing of direct-seeded rice using 40 kg/ha seed rate along with split application of 1/3rd N at first shower/enough moisture availability preferably after first weeding, 1/3rd N at maximum tillering and 1/3rd N at panicle initiation stage is an ideal and sustainable approach in terms of productivity and profitability under rainfed drought-prone environment of Eastern India.