Abstract
This study investigated if organic residues (rice straw and sugarcane bagasse) would increase crop yields and improve soil physical and chemical properties at both low and high levels of inorganic fertilizer on a mollisol for seven consecutive crops. During the seasons immediately after organic residue application, mulching with optimal inorganic fertilizer application or just nitrogen (N) (50 kg ha-1) substantially improved potato yields due to rapid emergence, larger and longer-duration canopy cover, lower soil temperatures and improved soil moisture retention. Incorporated organic residues with low levels of N resulted in reduced yields, primarily due to a larger C:N ratio. Bagasse without any inorganic fertilizer had a marked detrimental effect on growth. Nitrogen at 50 kg ha-1 plus rice straw, either as a mulch or incorporated into the soil, increased yields by 6 t ha-1 compared with yields without rice straw residues, and by 10 t ha-1 over treatments without nitrogen application. Mulching or incorporation of either rice straw or bagasse improved the soil water-holding capacity and bulk density. Bagasse, mulched or incorporated, resulted in higher soil organic matter content (OM); rice straw increased P and K levels. Residual effects of the organic materials did not influence subsequent crop yields. These results suggest that organic residues plus some inorganic N should be applied before each crop growing season to assure acceptable crop yields.
