Effect of Nitrogen on Growth, Yield and Nitrogen Use Efficiency of Aerobic Rice Grown at Tanjung Purun Lundu, Sarawak

Irrigated rice is the most important rice ecosystem which produces most of Malaysia’s rice supply. However, water scarcity and climate change has threatened the productivity of irrigated rice. Introduction of aerobic rice planting system may be the solution to improve the rice production in Malaysia. With proper management, this system could save 50% or more water consumption from irrigation than flooded rice. Besides, with the selection of right rice variety, aerobic system could solve the water inaccessibility issue, as in the case of rain-fed areas in Sarawak where water supply was not readily available due to the lack of irrigation system. Nutrient management is one of the most important management for aerobic rice system to thrive. In general, Nitrogen has been regarded as the single most critical element to improve rice production. Optimizing N level is critical for aerobic rice system to thrive since N forms and availability are different in this condition compared to flooded environment. Therefore, this study was conducted to determine the effect of different levels of nitrogen on growth; yield; and nitrogen use efficiency of aerobic rice in rain-fed Tanjung Purun, Lundu. Four Nitrogen levels (T1=0, T2=100, T3=200 and T4=300 kg N/ha) were tested in pot trial during off season of 2013/2014. Split urea (CO (NH2)2) fertilizer at 23%, 31%, and 46% for each rate was applied at 5, 25, and 45 days after emergence (DAE), respectively. Growth parameters measurement, yield and yield components performance and NUE were evaluated accordingly. There were no distinct differences on growth parameters when more N fertilizer was applied. However, treatments with N fertilizer applied performed better overall than T1. All plants in each treatment were intermediate stature in height with optimum height of 120 cm recorded in T2. Application of N fertilizer has affected tillering of aerobic rice to certain extent. Addition of more N fertilizer however did not improve tiller number mainly because genetically trait of MRIA1 only produces between 5 to 7 tillers per hill. Leaf N contents were improved with the increasing N levels. T2 and T3 recorded an optimum value of SPAD meter readings throughout the growth period. All growth parameters rapidly increased in vegetative stage (up until 55 DAE) before going linear and/or decreased towards maturity. This was mainly due to increased cell division and cell elongation in vegetative than in reproductive and maturation phases. Yield of aerobic rice in the study has been briefly affected by both filled spikelet percentage and number of panicle/m2. Improving NUEs (PFP, AE, RE, PE and IE) would also help to achieve desirable yield potential while at the same time preventing N lost to environment. However, in this study higher NUEs were obtained at lower N level. Based on this study, N application at 100 kg/ha was seen as a viable choice as it recorded highest yield (3.07 t/ha) with considerably better NUE values