Water Management, Nitrogen rate and Plant spacing effect on Yield and Yield components of Rice
Abstract
A study was conducted on a calcic vertisol to evaluate the main effects of water management, nitrogen (N) rate and plant spacing and their potential interactions on yield and yield components of rice. The experimental design was a split-split plot with two water treatments as main plots. Continuous flooding (CF) involved repeated ponding to 5 cm height and alternate wetting and drying (AWD) involved ponding to a height of 5 cm after the water level dropped to 25 cm beneath the soil surface. Nitrogen at 0, 90 and 120 kg N ha-1 served as subplots and three plant spacing (20 × 15 cm, 20 × 20 cm and 20 × 25 cm) as sub-subplots. The experiment was conducted during the major and minor rainy seasons over two years. A similar panicle density and grain yield was observed between AWD and CF, though AWD was characterized by a reduction in irrigation water used. This resulted in higher water productivity under AWD (0.284-0.899 kg m-3) relative to CF (0.257-0.810 kg m-3). Applying AWD saved between 9.5-11.3 % water relative to CF. There was no yield advantage for 120 kg N ha-1 over 90 kg N ha-1. There was no interaction between N rate and water management, suggesting that the effect of N rate was consistent regardless of the water management method. The rice plant did not sufficiently compensate for lower plant population in the minor rainy season compared with the major rainy season. As a result, the lower plant population (20 × 20 cm plant spacing) recorded lower yield than the higher plant population (20 × 15 cm plant spacing) in the minor rainy season. This also indicates that complete yield compensation is difficult or not guaranteed during the minor season at 20 × 20 cm plant spacing. Yield components were higher in the major rainy season resulting in higher yield in the major rainy season (3973 kg ha-1) than the minor rainy season (3550 kg ha-1). Therefore, establishing fields at 20 × 15 cm during the minor rainy season is recommended to increase tiller density to eventually increase or maintain yield. Also, employing AWD and applying N at 90 kg ha-1 can help farmers save water, avoid excessive N use and save cost.
