Effects of Cover Crop and Soil Amendment on Organic Rice Production.

Nitrogen supply and disease are two main challenges in organic rice production. Cover crop and soil amendment can be options to increase soil N while keeps rice health. The objective of this study was to test the effects of cover crop and soil amendment on the production of organic rice. Three popular cultivars, Presidio, XL753, and Tesanai, were grown. Our two-year study indicated that Cover crop had numerically increased rice grain yield while it was not significant. The tested two soil amendments had equal effect on organic rice production in terms of N supply. The grain yield of organic rice was significantly affected by the rate of N applied. Compared to 150 kg N/ha, the highest N rate of 210 kg N/ha had the same yield, indicating that 150 kg N/ha was sufficient for rice production in terms of N supply when land is managed in an organic system. Compared to Presidio and XL723, Tesanai had significantly higher grain yield and greater plant height. In addition, the severity of narrow brown leaf spot and brown spot was significantly higher (P<0.05) on Presidio and XL723 than on Tesanai. Under field conditions, cover crop treatments affected narrow brown leaf spot and brown spot with the most severe under fallow and least severe under clover. However, application of N did not affect the severity of narrow brown leaf spot and brown spot. Our field studies suggested that organic rice production can be improved through appropriate application of soil amendment and variety selection.