Soil carbon and nitrogen changes in long-term continuous lowland rice cropping
This long term study examines the effect of fertilizer on nitrogen levels and organic matter in submerged rice fields in the Philippines. Results demonstrate that soils which remain in continuous production benefit from fertilizer application over the first 17 to 21 years through increased levels of organic matter, nitrogen, and topsoil. However, in the following 15 years, measures of organic matter and nitrogen were increased or maintained regardless of fertilizer application. Overall, researchers concluded the results indicated that a balanced fertilizer regime for submerged soils maintained nitrogen and organic matter, and possibly even increased the latter.