Abstract
Seven field experiments were conducted at the Agronomy Field Laboratory of Bangladesh Agricultural University, Mymensingh during Boro and Aman seasons of 2005-2007 to study several factors of SRI viz. water management, fertilizer management, spacing, age of seedling, seedling storing time, date of transplanting, root placement and weed management. The results revealed that yield of rice increased under SRI technique in all experiments. SRI water management gave 17.93% more grain yield than BRRI water management. In SRI water management root growth was vigorous and deeper, which encouraged higher nutrients absorption thereby producing higher yield attributes and yield. Organic manure like cowdung @ 10 t ha1 and poultry manure @ 5 t ha1 did not perform well. A combined dose of 50% BRRI recommended fertilizer + 50% of poultry manure gave higher grain yield and yield attributes like number of panicles m2, effective tillers hill1 and grains panicle with exception of experiment No.1 and experiment No. 2. Where BRRI recommended fertilizer (120-60-40-10 and 5 kg ha N, P2O5, K2O, S and Zn, respectively) produced the highest grain yield. However, poultry manure at 5 t ha' was as good as cowdung at 10 t ha1 in respect of yield. The crop plant transplanted at spacing of 30 cm x 30 cm gave the highest yield despite lower number of panicles m2 than close spacing of 20 cm x 20 cm. However, the plants were able to compensate the yield loss in panicle density by making automatic adjustment between panicle length and number of grains panicle Too wide or too close spacing were not suitable for higher grain yield. Among three levels of age of seedling, the 12-day old seedling ranked top in respect of grain yield. Young seedling up to 12-day under SRI method produced higher grain yield than that of aged seedlings (30-days and 45-days) used in conventional system. On the other hand, seedling stored for 30 minutes, 2 hours, 4 hours and 8 hours after uprooting exerted no significant influence on yield and yield attributes except number of grains panicle. However, numerically the highest grain yield was obtained when rice seedlings were transplanted within 30 minutes after uprooting. From the result it revealed that it was better to transplant rice seeding as quick as possible in order to get higher grain yield. About root placement, the 'L' shaped root placement showed superior performance over 'J' shaped root placement in respect of most of the yield attributes and yield because plant shape more like as 'L' than 'J' with less energy was necessary for plant's growth and development. The date of transplanting significantly influenced the grain yield and other yield attributes of both Boro and transplant Aman rice. The rice plant transplanted on 15 January and 15 July gave the highest grain yield of Boro and transplant Aman rice, respectively which was the additive effect of their corresponding highest number of panicles m2, effective tillers hill1 and grains panicle1. SRI water management encouraged vigorous weed growth and required frequent weeding. Weed free condition, three weedings, two weedings and one weeding recorded 65.86%, 64.92%, 46.60% and 43.80% increase in grain yield over weedy check in Boro season while it was 67.28%, 66.65% and 63.50% under three weedings, two weedings and one weeding in T. Aman season. From the result it was revealed that two or three weedings were required to get higher grain yield for T. Aman and Boro rice, respectively. Under SRI technique, good management of soil, water, crop and nutrient management gave higher LAI, CGR and dry matter production which were ultimately reflected in higher grain yield. To maximize yield, integration of SRI techniques i.e. use of younger seedling, optimum plant population under optimum geometry, intermittent irrigation may be recommended for early transplant Aman and Boro rice.