Abstract:

【Objective】 The purpose of the study is to understand the general condition and spatial-temporal patterns of winter wheat harvest index and identify the main factors that contributed to harvest index (HI) changes of winter wheat in China. 【Method】 With observed data of winter wheat cultivation at agrometeorological stations between 1982 and 2005, HI of winter wheat and its relevant statistical parameters were calculated in different regions of China. Analysis was conducted on the inter-annual variability of winter wheat HI in Henan, Hebei and Shandong. Partial correlation between HI and three yield components and straw biomass were also statistically analyzed. 【Result】 For the recent twenty years, the average HI in China was 0.409 (±0.069, n=1 522), with 0.378 (±0.061, n=428) in 1980s, 0.408 (±0.070, n=657) in 1990s and 0.440 (±0.062, n=437) at present; it was averagely 0.408, 0.417 and 0.410 in Henan, Hebei and Shandong respectively. HI increased temporally in the dominant plantation region of China, at the rate of 0.066/10a (Henan), 0.044/10a (Shandong) and 0.032/10a (Hebei) accordingly. Results of partial correlation analysis showed the most significant negative correlation between harvest index and straw biomass. Significant positive correlation between harvest index and the three yield components were also exists but differed spatially. 【Conclusion】 Winter wheat harvest index showed spatial- temporal variations in China. Decreasing straw biomass contributed the most to harvest index gain, while 1000-kernel-weight contributed the least; the number of spikes and kernels per spike influenced harvest index in a positive but spatially different way.

Key words: winter wheat, harvest index, spatial-temporal variation