Impact of Integrated use of Rice Straw Mulch and Inorganic Fertilizers on Soil N,P,K and Organic Matter in Direct Seeded Lowland Rice(Oryza Sativa L.) Fields

Abstract

Abstract Integrated use of organic and inorganic fertilizers can improve the crop productivity and sustain soil health and fertility. This study evaluated the impact of a rice straw mulch (4t /ha rate) on soil nutrient status in dry- direct seeded rice (DDSR) and wet- direct seeded rice (WDSR) fields with recommended rates of N, P and K mineral fertilizers in the Anuradhapura District, a major rice growing area of Sri Lanka. Total N, available P, extractable K and soil organic matter content (SOM) was measured at planting, 35 days after sowing, panicle initiation and at harvesting. Application of a rice straw mulch to WDSR, significantly increased the extractable K content in the top 0-10 cm of soil (i.e. 112.6 ppm in dry season (DS), 119 ppm in wet season (WS)), when compared to chemical weeded WDSR (i.e. 76.1 ppm in dry season and 99.8 ppm in wet season) at the panicle initiation stage. The K release was greater over the first 35 days after rice straw application in both seasons. The SOM changes were minor during 2 years of treatment application. Although the percentage of total N was significantly high in WS, it did not vary among treatments of study. The available P content was not significant in DS in treatments and in WS the available P content was significantly reduced in the rice straw treated WDSR plots. The study indicated the possibility of enhancing the soil extractable K stocks in WDSR by integrated use of rice straw mulch and mineral fertilizers in both seasons in this region.