SINGLE BASAL APPLICATION OF TOTAL NITROGE N-FERTILIZER WITH CONTROLLED-RELEASE COATED UREA ON NON-TILLED RICE CULTURE

Single application of total nitrogen fertilizer with controlled-releas e coated urea on non-tilled rice culture (LP-plot) was compared with a conventional application method using easily released nitrogen fertil izer, ammonium sulfate (AS), for both basal and top-dressing (AS-plot) . The results obtained were as follows. 1) The growth of rice on LP-pl ot was relatively inferior to that on AS-plot in the young seedling st age, but superior in plant height, leaf color, number of tiller and dr y weight after the beginning of June. 2) A drastic reduction of soil m ineral nitrogen due to denitrification occurred in AS-plot just after submerging, and severe nitrogen deficiency of rice, chlorosis, lasted until the top-dressing stage, whereas rice on LP-plot showed normal gr owth at all times. 3) Brown rice yields of LP-plot in 1990 with a hot summer and in 1991 with a cool summer were 57.1kg/a or 155% of AS-plot and 51.2kg/a or 133% of AS-plot, respectively. The drastic reduction in grain yield of AS-plot seems to be related to decrease of numbers o f ears reflecting nitrogen deficiency of plant at the vegetative growt h stage. 4) Amounts of nitrogen uptake of rice plants on LP-plot were somewhat inferior to that on AS-plot in the early growth period, but w ere extremely superior after the active-tillering stage and reached 1. 57 times of that on AS-plot at the maturing stage. Recoveries of contr olled-release coated urea for basal application, AS for basal applicat ion, AS applied at panicle formation stage and AS applied at full head ing time were 63.2%, 8.5%, 52.8%, and 41.5%, respectively. 5) From the foregoing, we conclude that a single basal application of total nitro gen fertilizer on a non-tilled rice culture is highly effective using controlled-release coated urea.