Abstract
Nine field experiments were conducted at the Agronomy Field Laboratory of Bangladesh Agricultural University, Mymensingh during both Aman and Boro seasons of 2004-2006 to study several factors of SRI viz. fertilizer management, spacing, seedling age, seedlings hill⁻¹, water management, seedling raising method and weed management. The results revealed that the yield of rice increased under SRI packages in all experiments. Cow dung at low doses did not perform well rather a dose of 17 t ha⁻¹ was found moderate. A combined dose of 10 t ha⁻¹ cow dung plus BRRI recommended fertilizer dose (N, P₂O₅, K₂O, S and Zn @ 140.00, 15.31, 29.64, 5.11 and 1.77 kg ha⁻¹) produced the highest grain yield, which was statistically identical with 10 t ha⁻¹ cow dung plus 150% BRRI recommended fertilizers. So, the latter dose may not be economically viable. An integrated dose of 15 t ha⁻¹ cow dung plus 50% BRRI recommended fertilizers was also suitable for having high yield of rice. A combined dose of 10 t ha⁻¹ cow dung with at least 50% BRRI recommended fertilizers was also found to produce a good yield under SRI package. In Experiments 2 and 8, respectively 22.35% and 36.42% more grain yields were obtained from the treatment with all SRI factors than the conventional method and grain yield increased with the gradual increase in number of SRI levels. In these two experiments the grain yield was statistically identical from one and two level to all level SRI practices, respectively. This clearly reveals that 28 and 17 options including all SRI practices, respectively have emerged from the study which can give as good yield as SRI. Results with spacing experiments proved that 30 cm × 30 cm spacing was the most appropriate. However, in two experiments, 40 cm × 40 cm and in another experiment, 35 cm × 30 cm spacings were also found suitable for producing good yield. On the other hand, too wide or too close spacings were not favourable for having high yield. Among three levels of seedling ages, eight-day old seedlings produced higher grain yield, straw yield and biological yield than that of 12-day or 16-day old seedlings. Young seedlings up to 16 days under SRI method always produced higher grain yield than that of aged seedlings (30-day and 45-day) used in conventional method. In most of the experiments, one seedling hill⁻¹ was found to generate more number of effective tillers hill⁻¹ and ultimately this contributed to higher grain yield. In Experiment 7, two seedlings hill⁻¹ gave higher grain yield than that of one and three seedlings. The SRI water management gave 38.79% higher grain yield than conventional water management. Hybrid variety Jagoron with SRI water management produced higher grain yield than each of conventional (flood irrigation with standing water) and modified SRI water management practices (saturated for one month, then different levels of irrigation until drying followed by further irrigation). Jagoron produced 27.94% and 7.11% higher grain yield respectively than each of BRRI dhan28 and BRRI dhan29. The highest grain, straw and biological yields were produced by dapog seedlings, probably because these seedlings were least affected by transplanting shock. Seeding with germinated seeds was also found suitable for high yield. A spacing of 30 cm × 30 cm along with weekly soil stirring by Japanese rice weeder gave higher grain yield than any other treatment combinations. The results indicated that rice yield enhanced to a considerable extent in all treatments of SRI and in particular, the response was more pronounced in Boro season than in Aman season.