Changes in Soil N, P, K, Rice Growth and Yield Following the Application of Azolla pinnata

Abstract

Information on the effects of A. pinnata application on changes in nutrient availability and rice yield obtained from paddy fields of the South Lampung, Indonesia is still limited. A study was carried out to investigate the effects of different rates of A. pinnata (0; 2.5, 5.0, 7.5, and 10.0 t/ha) on changes in N, P, K concentrations in paddy soils, N uptake, rice growth and yield. The experiment was conducted on a well-irrigated paddy field that was incorporated with A. pinnata, and then rice seedlings of Ciherang variety had been grown on it from June up to December 2009. The results showed that the application of A. pinnata to the paddy rice fields affected the soil available P, plant height, tiller number, grain number per panicle, and grain yield. The addition of A. pinnata at the rate of 5.0 and 7.5 t/ha had higher rice yield compared with other treatments. The application of A. pinnata at the rate of 7.5 t/ha increased significantly soil available P, indicating that A. pinnata required a fairly high P to grow optimally. The application of A. pinnata at the rate of 7.5 t/ha gave also the highest dry grain yield, suggesting that the application of A. pinnata did not suppress the rice yield, even it might help to conserve fossil fuels and foreign exchange as well as allow more paddy fields that can be fertilized by N. Practically, the application rate of A. pinnata could range 4-8 t/ha, depending on the abundance of the material at the site.

Keywords: Azolla pinnata, organic matter, rice growth and yield, soil nutrients