Straw Application Effects on Methane and Oxygen Exchange and Growth in Rice

Abstract Currently, there is a paucity of information on plant‐soil interactive effects and plant‐related factors that control CH 4 production and its emission from rice ( Oryza sativa L.) paddies. Laboratory studies were conducted to evaluate the effects of rice straw application rates on growth, root porosity (POR), and gas (O 2 and CH 4 ) exchange in rice under continuously flooded conditions. Three rice cultivars were grown in Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf) amended with two levels (11 and 22 t ha −1 ) of rice straw. Plants were harvested for growth, POR, and radial oxygen loss (ROL) estimates at 40 d after transplanting. Methane measurements were made at 20, 30, and 40 d after transplanting. Plant growth and straw application rates were negatively correlated. Variations existed among cultivars in parameters studied. Although POR was enhanced by the higher application rate (22 t ha −1 ), reductions in shoot and root growth consequently resulted in reduced ROL. Two of the cultivars exhibited significant POR‐ROL correlations. Highest CH 4 emissions occurred at the 11 t ha −1 application rate. At the 22 t ha −1 application rate, CH 4 emissions were significantly reduced in all vegetated treatments, although emissions from unvegetated treatments were enhanced. Results indicated that reductions in CH 4 emissions at the higher straw application rate resulted from reduction in the total diffusive pathway of the gas and were not due to the mitigation of methanogenesis.