Growth and Yield of Rice (Oryza sativa L.) Applied With Straw from Different Rice Varieties under Varying Water Regimes and Fertilizer Levels

The effects of straw incorporation, soil water condition (flooded and non-flooded) and rate of fertilizers (low and high) on the availability of nutrients, dry matter and rice grain yield were examined. Straw of rice varieties Soc Nau and IR67962 collected from the field and straw of IR30, collected from a glasshouse experiment, were incorporated to an Alfisol sandy loam soil at an application rate of 5 t ha(-1). A no-residue control treatment was also included. Straw dry matter and grain yield were higher under flooded than non-flooded conditions and the higher fertilizer rate produced higher yield. Each variety resulted in reduced straw yields at active tillering because of strong negative apparent recoveries of nitrogen and phosphorus. At maturity incorporation of Soc Nau and IR67962 straw increased straw dry matter yield in the rice crop by 11% over the no-residue control. Grain yield was increased by 25, 18 and 12% in the IR67962, Soc Nau and IR30 treatments, respectively. Soc Nau straw had the highest nitrogen, phosphorus and sulfur concentration, the highest straw quality index (SQI) and the narrowest carbon:nitrogen among the straws. Straw of IR67962 had the highest potassium, lignin:nitrogen ratio and the lowest SOL By contrast IR30 had deficient concentrations of sulfur and potassium, the highest digestible organic matter and highest labile carbon. The anticipated decomposition effects were modified by the availability of nutrients from the straw and/or the amount of immobilization of nutrients that took place.