Effects of straw incorporation method on double cropping rice yield and the top-three leaf characteristics

Experiments were conducted on early rice "Luliangyou 996" and late rice "Wufengyou T025" during the double cropping seasons of 2010-2011 to study the effects of different methods of straw incorporation into soil on yield and top-three leaf characteristics of rice. The results showed that compared to non-straw incorporation, incorporating straw into soils significantly increased grain yield of early rice under equal NPK fertilization. However, straw incorporation was not significantly different from non-straw incorporation in terms of grain yield of late rice. Rice yield in straw-incorporated soils was significantly higher than non-straw incorporated soil under non-fertilization treatments in both early and late rice seasons. Straw incorporation ameliorated the characteristics of top-three leaves of double cropped rice, with higher optimization effect on early rice than on late rice. A significant relationship (P < 0.05) was noted between straw incorporation and grain yield. The index of the top-three leaves of early rice under non-straw incorporation was optimum when yield was maximum, which was not so obvious for late rice. Straw incorporation strengthened the quality of the top-three leaves of double cropped rice with a parabolic relationship between leaf area and leaf area rate of the top-three leaves with grain yield. A highly significant linear relationship was also noted between the specific leaf area and grain yield. The results suggested that rice yield increase under straw incorporation was mainly driven by the perfect structure of top-three leaves of double cropping rice.