Mass-Based Image Analysis for Evaluating Straw Cover Under High-Residue Farming Conditions in Rice–Wheat Cropping System

Estimation of crop residue distribution in paddy fields is extremely crucial especially in tight crop rotation areas that produce large volumes of straw causing germination problems in the following crop. Our objective was to develop an accurate and easy-to-handle field method to quantify the proportion of ground cover. Mass and cover relationships were investigated and analyzed to evaluate straw distribution on the soil surface, by comparing surface cover from three different combine harvesters in a rice–wheat (R–W) cropping system. For each harvester, straw distribution on the ground was measured and virtually reconstructed, and then the straw stacked layers analyzed. The mean straw mass distribution and percent surface cover measured in 2014 and 2015 ranged between 4200–12,000 kg/ha and 60–97%, respectively, for all the harvesters. Flat straw mass was higher than standing stubble mass in all treatments. The most important observation is that the distribution pattern of straw depended on instantaneous material feed rate through the harvester; the higher the feed rate, the poorer the straw distribution uniformity. The Xinjiang Ceres 4LZ-2.5 harvester outperformed all the other harvesters. These findings can improve the estimation of straw cover for tillage straw incorporation or no-till straw return fields and indicates that straw condition should be considered in mass-to-cover relationships.