IMPACT OF RICE STRAW MANAGEMENT ON SOIL PHYSICAL-PROPERTIES AND WHEAT YIELD

Field experiments were conducted for 5 years, starting from the dry season of 1984-85, to study the effects of rice straw management practices such as straw incorporation, straw mulch, straw burning, farmyard manure incorporation, farmyard manure plus straw incorporation, and no straw as control on soil physical properties and yield of winter wheat (Triticum aestivum L.). The rate of rice straw and farmyard manure was 5 t.ha-1. The soils of the site are classified as clayey thermic typic Hapludalf with pH 5.8; organic C 0.66 percent; cation exchange capacity 11.8 cmol P+ 100(-1) g; hydraulic conductivity of the saturated soil 0.80 x 10(-6) ms-1 in the surface (0-0.3 m) depth. The treatments of farmyard manure and farmyard manure plus straw incorporation had higher percentage of water stable aggregates > 0.25 mm diameter (80.9 percent, larger mean weight diameter (0.82 mm), higher porosity (54.2 percent, lower bulk density (1.19 Mg.m-3), higher available water capacity (0.125 m3.m-3, and higher hydraulic conductivity of saturated soil (3.21 x 10(-6) ms-1). The soil temperature at 0.1-m depth was not substantially affected by any of the treatments under study except the straw mulch where minimum temperature was raised by about 2-degrees-C over the control. The improvement in physical properties coupled with supply of nutrients from farmyard manure and rice straw resulted in consistently higher grain yields under farmyard manure plus straw incorporation followed by farmyard manure and straw mulch for the 5 years. The grain yields under straw burning, straw incorporation, and control were comparatively low.