AEROBIC RICE'S YIELD PERFORMANCE AND NITROGEN USE EFFICIENCY UNDER VARIOUS NITROGEN FERTILIZER RATES

Abstract

Aerobic rice, a water-saving cultivation system rice could thrive well in rain-fed areas in Sarawak which lacks in drainage and irrigation system, with appropriate fertilizer management practices. Since nitrogen (N) as a major determinant factor in rice yield is required differently based on cultivation system, soil and other in-situ conditions, a study was conducted to determine the optimum N fertilizer rate while assessing nitrogen use efficiency of aerobic rice in Lundu, Sarawak. Four N fertilizer rates (T1=0, T2=100, T3=200 and T4=300 kg N/ha) were tested with split application of urea (46% N) at 23%, 31%, and 46% at 5, 25, and 45 days after emergence (DAE) using MRIA1 variety. The findings indicated that an increase in N fertilizer of more than 100 kg N/ha had no discernible impact on yield. The highest yield recorded was 3.31 t/ha in T2 and decreased to 2.99 t/ha and 2.86 t/ha respectively in T3 and T4, while T1 recorded 1.12 t/ha. Meanwhile, significant differences in partial factor productivity (PFPN), agronomic efficiency (AEN), apparent recovery efficiency (REN) and physiological efficiency (PEN) were observed between the treatments with descending efficiency trends at higher N fertilizer rates. Optimum NUE values were recorded in T2 with PFPN = 29.30 kg/kg; AEN = 14.56 kg/kg; REN = 0.26 kg/kg; and PEN = 55.64 kg/kg. Therefore, it can be concluded that 100 kg N/ha is recommended for aerobic rice cultivation in Tanjung Purun, Lundu, as yield and NUEs were optimized.