Successive straw biochar amendments reduce nitrous oxide emissions but do not improve the net ecosystem economic benefit in an alkaline sandy loam under a wheat–maize cropping system. (23rd December 2019) - Liu, Yujuan
Abstract: Crop straw is converted to biochar with subsequent applications to soils as a multi‐benefit strategy for greenhouse gas (GHG) emission mitigation, carbon sequestration, and straw disposal and utilization in intensive agriculture. However, tradeoffs between agronomic, economic, and environmental performance of long‐term agricultural biochar use remain unclear. Using a case study of biochar‐amended alkaline sandy loamy soil, we investigated the effects of field application of straw biochar at 0, 2.25, 6.75, and 11.25 Mg ha −1 to 10 successive wheat and maize crop seasons over five rotation years on crop yield, nitrous oxide (N2 O) emissions, soil total organic carbon (TOC), and soil carbon pool (SCP). The net global warming potential (net GWP) and net ecosystem economic benefit (NEEB) were assessed to examine the tension between balancing economic returns and environmental benefits. Results indicated that biochar treatments slightly increased total crop grain yields and greatly reduced the total N2 O emissions over five rotation years. The soil total organic carbon content was enhanced while the CO2 emissions during biochar production almost offset the increase in the soil carbon pool. Economic assessment showed that the net ecosystem economic benefit was lowered with enhanced costs of the increasing biochar use under the current low C trade market. These results highlight the promotion of the use of straw biochar in successive applications as a strategy to effectively offset greenhouse gas emissions from agriculture requires optimization of the straw pyrolysis system to reduce the energy consumption and overall biochar costs, and price enhancement of C trade.