摘要:垄作和秸秆覆盖是实现西南丘陵区旱地农田稳产高产和固碳的适宜保护性耕作模式。为探讨该保护性耕作模式下蚕豆/玉米/甘薯三熟制农田土壤碳排放的特征，对平作无覆盖（T）、垄作无覆盖（R）、平作+秸秆半量覆盖（TS1）、垄作+秸秆半量覆盖（RS1）、平作+秸秆全量覆盖（TS2）、垄作+秸秆全量覆盖（RS2）6种耕作模式下西南紫色土丘陵区蚕豆/玉米/甘薯三熟制农田土壤呼吸、粮食产量特征进行测定，分析农田碳平衡及经济-环境效益，为量化评估农田生态系统碳收支提供理论依据。结果表明：在整个间套作系统内，蚕豆、玉米和甘薯全生育期内土壤呼吸速率均值分别为3.704 μmol·m-2·s-1、4.847 μmol·m-2·s-1和4.606 μmol·m-2·s-1，垄作降低了3种作物的农田土壤呼吸速率（P < 0.05），秸秆覆盖则增加了土壤呼吸（P < 0.05），垄作和秸秆覆盖配合使用后土壤呼吸总量和微生物呼吸总量增加（P < 0.05）。保护性耕作促进三熟制农田生态系统内作物固碳；土壤-作物系统碳平衡表现为碳汇，RS2、TS2、RS1、TS1、R分别较T高25.41%、25.37%、9.84%、26.74%、13.26%。与平作相比，垄作和秸秆覆盖提高了粮食产量，以RS2（17 460.45 kg·hm-2）最高，TS2（16 498.73 kg·hm-2）次之。蚕豆/玉米/甘薯三熟制农田生产每千克籽粒释放CO2量处理间表现为T（1.88 kg·kg-1）> TS1（1.83 kg·kg-1）> R（1.76 kg·kg-1）> TS2（1.75 kg·kg-1）> RS1（1.69 kg·kg-1）> RS2（1.68 kg·kg-1）。垄作和秸秆覆盖提高了套作的经济-环境效益，秸秆覆盖量越高，经济-环境效益越好。从农田碳平衡和经济-环境效益综合考虑，垄作结合秸秆全量覆盖（RS2）具有最大的碳汇能力和最优的经济-环境效益，可以优先作为该地区农田实现固碳增汇减排的耕作措施。
关键词:土壤呼吸/
碳平衡/
碳汇/
经济-环境效益/
蚕豆/玉米/甘薯三熟制/
保护性耕作
Abstract:Ridge tillage and straw mulching are suitable modes of conservation tillage that increase crop productivity and sequestrate carbon in the purple hilly region of Southwest China. A field experiment was conducted with six treatments-traditional tillage without straw mulching (T), ridge tillage without straw mulching (R), traditional tillage with straw mulching at 3 750 kg·hm-2 (TS1), ridge tillage with straw mulching at 3 750 kg·hm-2 (RS1), traditional tillage with straw mulching at 7 500 kg·hm-2 (TS2) and ridge tillage with straw mulching at 7 500 kg·hm-2 (RS2). The characteristics of soil respiration, carbon balance, crop yield, and economic and environmental benefits for the triple intercropping system of fava bean, maize and sweet potato were evaluated. The study provided the theoretical basis for quantifying carbon budget of farmland ecosystems in the region. It was noted that mean soil respiration rates during growth period of fava bean, maize and sweet potato were 3.704 μmol·m-2·s-1, 4.847 μmol·m-2·s-1 and 4.606 μmol·m-2·s-1, respectively. Ridge tillage reduced soil respiration rate during growth period of three crops, whereas straw mulching increased it (P < 0.05). Ridge tillage with straw mulching increased cumulative soil respiration and cumulative microbial respiration (P < 0.05). All treatments of conservation tillage improved carbon sequestration of crops in the triple intercropping system. The soil-crop system exhibited carbon sink and the treatments of RS2, TS2, RS1, TS1 and R significantly increased carbon sequestration respectively by 25.41%, 25.37%, 9.84%, 26.74% and 13.26%, compared with treatment T. Ridge tillage and straw mulching treatments increased total crop yield of the triple intercropping system, which was highest under RS2 (17 460.45 kg·hm-2) and next TS2 (16 498.73 kg·hm-2). The amount of CO2 released from soil per 1 kg grain in the triple intercropping system was in the order of:T (1.88 kg·kg-1) > TS1 (1.83 kg·kg-1) > R (1.76 kg·kg-1) > TS2 (1.75 kg·kg-1) > RS1 (1.69 kg·kg-1) > RS2 (1.68 kg·kg-1). This meant that both ridge tillage and straw mulching increased the economic and environmental benefit index. The more straw was added during mulching, the more was the economic and environmental benefits. In conclusion, the RS2 treatment (ridge tillage + straw mulching at 7 500 kg·hm-2) had the largest carbon sink capacity and the optimal economic and environmental benefits. Thus, it was recommended for adoption as tillage pattern to increase carbon sequestration and reduce carbon release in the study area.
Key words:Soil respiration/
Carbon balance/
Carbon sequestration/
Economic and environmental benefits/
Fava bean, maize and sweet potato triple intercropping system/
Conservation tillage
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