A SINGLE BASAL APPLICATION OF CONTROLLED- RELEASE COATED UREA TO RICECULTURES USING POT SEEDLINGS IN A COOL REGION

A low-cost, high yielding culture of rice was studied by the applicati on of controlled-release coated urea (CU) to pot seedlings (PS)-raised in a pot culture nursery box-cultivated in a cool region, and compare d to the application of conventional fertilizer (CF) to pot seedling ( PS) and mat seedlings (MS)-raised in a broadcast seeding nursery box. The plant length and the number of tillers per hill in the PS plots we re longer and larger than those in the MS plots due to the superior ch aracteristics of the seedlings. However, the number of tillers/m(2) in the PS plots was less than that in the MS plots. Reflecting the nitro gen released from the coated urea, the plant length and number of till ers/m(2) in the PS-CU plots were inferior to those in the PS-CF and MS -CF plots at the early growth stage. However, after the neck node diff erentiation stage, these were reversed due to the increased release of nitrogen from the coated urea. As a result, the leaf color value and dry weight of the rice in the PS-CU plots were higher than those in th e PS-CF and MS-CF plots. The yields of brown were in the following ord er:PS-CU plot>PS-CF plot>MS-CF plot. The number of panicles and spikel ets were Larger in the PS-CU plot than those in the PS-CF and MS-CF pl ots, which might affect the increased yield. It seems that the photosy nthetic activity of the rice plants in the PS-CU plot was maintained a t a high rate throughout the ripening stage. The nitrogen uptake and e fficiency of the applied fertilizer were in following order:PS-CU plot >PS-CF plot>MS-CF plot. The recovery of basal nitrogen in coated urea (63 similar to 68%) was much greater than that of ammonium sulfate (30 similar to 40%), and greater than the recovery of the top dressed nit rogen of ammonium sulfate (41%similar to 59%).