Crop cleaner production improvement potential under conservation agriculture in China: A meta-analysis

Abstract

Conservation agriculture has been regarded as an efficient and clean management to increase crop production. However, the effectiveness of various conservation agriculture practices with respect to crop production is a controversial subject. In addition, calculating the overall effect of conservation agriculture in terms of crop production improvement by averaging the whole dataset is not uncommon, but field results should be weighted by the geographic regions and the effectiveness of various conservation agriculture combinations on crop cleaner production improvement based on weighted cropping region areas should be evaluated. In this study, we assessed and compared the effectiveness of various conservation agriculture practices in different cropping regions and among different crop types, followed by a comprehensive evaluation of how the combinations of conservation agriculture practices could potentially impact on crop yield improvement and carbon emission in China. The results showed that conservation agriculture practices were highly region-dependent: single conservation agriculture component was more suitable for the South, whereas straw mulching itself or combined with tillage reduction including no tillage and reduced tillage had significantly extraordinary performance in the North. Conventional tillage with straw mulching was the only conservation agriculture practice that led to significant increase of crop yield in all the cropping regions across China. We further found that the previously reported positive correlation between relative changes of yield and prolonged experimental duration could only be applied to conservation agriculture practices that had positive impact on crop production. The negative relationship between crop yield changes and annual precipitation was actually only observed for no tillage with straw mulching. These results demonstrate the different responses of conservation agriculture practices to various cropping region, crop types, climatic conditions, and application duration. Moreover, the results showed that the optimal combination of conservation agriculture for yield had a huge potential to increase crop production by 21.49% across China, which was higher than any of the single conservation agriculture practices. However, if the improper conservation agriculture practices were combined, it may lead to a crop yield decline by −2.30%. The combination for clean production could lead to an increase of crop yield by 6.89% and carbon emission reduction by 75%. Overall, this study illustrates that using single conservation agriculture practice is very likely to underestimate the increase potential of crop production, and the conservation agriculture management should thus be regarded as a package of tillage practices determined by yield improvement and carbon emission reduction according to cropping regions of different climatic conditions and crop types.