Author : Khin Myo Thant

Summary : This study evaluated the effect of different levels and timings of nitrogen (N) application and row spacings as well as a combination of these factors on bending resistance and yield of aerobic rice. Two field experiments were conducted during the 2004 wet season in Central luzon Philippines, using the Apo cultivar planted at three different row spacings: 25, 30, and 35 cm. The first experiment involved N level (NL) and row spacing (RS) in Bulacan and Tarlac. The second experiment involved N split (NS) application and row spacing in PhilRice and IRRI. For the N level experiment, five N levels were used: 0, 60, 90, 120 and 150 kg ha. On the other hand, 100kg ha was applied in five splits for the NS x RS experiment. Experimental results revealed that bending resistance and grain yield were not affected by varying row spacings (25-35 cm). Specifically for grain yield, higher panicle number per square meter in 25 cm row spacing and higher spikelet number per panicle in 35 cm row spacing were observed. Generally, grain yields increased with NL up to 90 kg ha. Beyond this N level, the risk of lodging may pose a problem. Splitting of N did not affect bending resistance and yield of aerobic rice during the wet season. While the optimum combination of N level, N split, and row spacing on bending resistance and yield of aerobic rice was not identified, results suggested that farmers may grow aerobic rice using row spacings within 25-35 cm as long as this row spacing may not interfere with other cultural management practices. Farmers may apply N in three splits with flexible amounts for the selected crop stages : at 10-14, at 30-35, and at 45-50 days after emergence (DAE). total N application for the whole growing period during the wet season can be 90 kg ha or higher if there is no risk of lodging.