A global meta-analysis of soil organic carbon response to corn stover removal

Abstract

Corn (Zea mays L.) stover is a global resource used for livestock, fuel, and bioenergy feedstock, but excessive stover removal can decrease soil organic C (SOC) stocks and deteriorate soil health. Many site￢ﾀﾐspecific stover removal experiments report accrual rates and SOC stock effects, but a quantitative, global synthesis is needed to provide a scientific base for long￢ﾀﾐterm energy policy decisions. We used 409 data points from 74 stover harvest experiments conducted around the world for a meta￢ﾀﾐanalysis and meta￢ﾀﾐregression to quantify removal rate, tillage, soil texture, and soil sampling depth effects on SOC. Changes were quantified by: (a) comparing final SOC stock differences after at least 3ￂﾠyears with and without stover removal and (b) calculating SOC accrual rates for both treatments. Stover removal generally reduced final SOC stocks by 8% in the upper 0￢ﾀﾓ15 or 0￢ﾀﾓ30ￂﾠcm, compared to stover retained, irrespective of soil properties and tillage practices. A more sensitive meta￢ﾀﾐregression analysis showed that retention increased SOC stocks within the 30￢ﾀﾓ150ￂﾠcm depth by another 5%. Compared to baseline values, stover retention increased average SOC stocks temporally at a rate of 0.41ￂﾠMg Cￂﾠha￢ﾈﾒ1ￂﾠyear￢ﾈﾒ1 (statistically significant at pￂﾠ<ￂﾠ0.01 when averaged across all soil layers). Although SOC sequestration rates were lower with stover removal, with moderate (<50%) removal they can be positive, thus emphasizing the importance of site￢ﾀﾐspecific management. Our results also showed that tillage effects on SOC stocks were inconsistent due to the high variability in practices used among the experimental sites. Finally, we conclude that research and technological efforts should continue to be given high priority because of the importance in providing science￢ﾀﾐbased policy recommendations for long￢ﾀﾐterm global carbon management.