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.
