Aerobic rice response to irrigation regimes and fertilizer nitrogen rates.

Abstract

Rice production in aerobic conditions holds promise in Asia especially in the era of increasing irrigation water scarcity. Field experiments were conduceted on aerobic rice systems at the research farm of the Directorate of Water Management (ICAR), Bhubaneswar, India, during dry seasons of 2007-2008 to 2009-2010 to evaluate different irrigation regimes and water saving potential in aerobic rice compared to traditional flooded rice, varietal performance and fertilizer N-rates. Results revealed that the rice varieties viz. ‘Surendra’, ‘Apo’ and ‘Lalat’ showed the highest yield potential between 3.9 to 4.6 t ha-1 under aerobic conditions with soil moisture at 80-90% of field capacity throughout the growing season. These varieties were suitable for growing under aerobic condition because of favorable physiological characteristics and crop yield. Water input as a pre-sowing irrigation was estimated as 54-62 mm for aerobic rice, and 362-401 mm for wet land preparation for traditional flooded rice. On average, water input during crop growth stage was 506 mm for aerobic rice and 882 mm for traditional flooded rice. In total, saving potential of water input was 42-60% with aerobic rice when compared to traditional flooded rice. The grain yield was 2.39-3.36 t ha-1 under aerobic irrigation regimes, with the highest being with irrigation at 80-90% of field capacity of soils. Results showed a reduction in yield under aerobic conditions as compared to traditional flooded. This yield reduction was 16% with irrigation at 80-90% of field capacity. However, estimated water productivity, with respect to rainfall and irrigation water input, increased in aerobic rice (4.71 kg grain ha-1 mm-1) compared to traditional one (3.04 kg grain ha-1mm-1). Studies on irrigation x N interaction revealed that a highest grain yield of 4.4 t ha-1 was obtained with N rate of 120 kg ha-1 receiving 780 mm irrigation for rice variety ‘Surendra’. The next best combination viz. N rate of 80 kg ha-1 with 780 mm irrigation (3.84 t ha-1) and N rate of 120 kg ha-1 and 660 mm irrigation (3.61 t ha-1) were statistically similar. Hence, based on availability of irrigation water, N rate needs to be decided. The study on varietal (viz. ‘Apo’, ‘Lalat’ and ‘Surendra’) response to N rates showed that, irrespective of variety, aerobic rice with 120 N kg ha-1 with 780 mm irrigation gave the highest grain and straw yield of 4.24 and 6.63 t ha-1 with grain and straw N-uptake of 52.17 and 52.63 kg ha-1, respectively.