Effects of controlled release fertilizer on rice yield and N recovery

Field experiment was conducted at Tsuruoka City, Yamagata Prefecture, Japan in 1998 15N trace method was used to test the effects of polyolefin coated urea (controlled release fertilizer) as basal on rice yield, the pattern of N absorption and N recovery rate compared with urea and ammonium sulfate with split application Results indicated that: 1) For transplanting rice, the highest yield was obtained by the blend of urea and LPS-100 in the ratio of 1:1 as basal, and increased by 23.6% and 9.2% compared with urea and ammonium sulfate, respectively For the direct seeding rice the highest yield was obtained by LP-100 as basal, and increased by 9.2% and 4.0% compared with urea and ammonium sulfate, respectively Controlled release fertilizer treatments could give more effective panicles and filled grains of rice than urea and ammonium sulfate treatments 2) No significant difference was observed in total N uptake among fertilizer treatments But the N accumulation from transplanting (or seeding) to panicle initiation in plants treated with controlled fertilizer were much more than conventional fertilization, resulting in the greater number of panicles per unit area and filled grains per panicle 3) 15N labeled experiment indicated that up to maximum tiller stage N absorption of rice from basal fertilizer of urea and ammonium sulfate accounted for 33%～45% of total N absorption from basal fertilizer only N uptake from basal fertilizer lasted to heading stage in urea or ammonium sulfate plots and to harvesting stage in LP-100 plot While N uptake from topdressing applied at panicle initiation stage completed on 45 days after application 4) The total N recovery rate tested using 15N method was higher in urea plot than ammonium sulfate and LP-100, while that tested using difference method was higher in the LP-100 than other treatments The N recovery rate of basal fertilizer was in the order of LP-100ammonium sulfate urea Basal application of urea/LPS-100 blend and LP-100 had higher physiological and agronomic efficiency of N than urea and ammonium sulfate, that may be the main reason for getting high yield by controlled fertilizer in the trail