Effects of water and straw mulching on soil respiration and carbon balance in summer maize farmland

【Objective】 The purpose of this paper is to give full play to the respective advantages and synergistic effects of straw mulching and suitable irrigation on crop yield and soil carbon sequestration and emission reduction, establish an efficient farmland management mode of emission reduction, increase, and water saving. 【Method】 Taking summer maize in Western Henan as the research object, the mulching method and the lower limit of irrigation water were tested. The mulching method was straw mulching (S) and no mulching (N). The lower limit of irrigation water was set at four levels: 50% (W1), 60% (W2), 70% (W3) and 80% (W4) of field water holding capacity. Soil respiration, crop biomass and grain yield under different treatments were systematically studied. The total amount of soil carbon emission, the amount of soil microbial isooxygen respiration carbon release and the amount of carbon sequestration of farmland net primary productivity were calculated. Farmland net ecosystem productivity (NEP) was calculated as the carbon sequestration of farmland net primary productivity and the carbon release of soil microbial iso-respiration. Carbon emission efficiency (CE) calculated from crop yields and soil carbon emissions reflected the economic and environmental benefits of farmland. NEP and CE were used to objectively evaluate the effects of straw mulching and different irrigation lower limits on crop yield and carbon sequestration. 【Result】 The soil respiration rate of SW4 treatment was the highest and that of NW1 treatment was the lowest. Soil respiration rate of SW4 treatment reached the highest value at anthesis stage 6.08 μmol/(m2·s), and there was no significant difference between SW3 treatment and NW4 treatment. Compared with NW1 treatment, straw mulching and irrigation increased the amount of carbon sequestration in farmland net primary productivity and the amount of soil microbial iso-respiratory carbon release, and that of SW4 treatment was the highest, with no significant difference compared with SW3 treatment and NW4 treatment. SW3 treatment had the highest NEP which was 3.99%-245.74% higher than that of other treatments and the highest CE which were 2.35%-138.80% higher than that of other treatments. Compared with SW4 treatment, NEP of SW3 treatment increased by 2.99% and CE of SW3 treatment increased by 2.35% under the premise of saving irrigation. 【Conclusion】 The lower limit of irrigation water is 70%FC and straw mulching (SW3) treatment, which can effectively coordinate the yield and carbon emission efficiency of summer maize farmland system, promote higher crop yield, achieve higher net ecosystem productivity and carbon emission efficiency, and reduce the carbon emission generated in the production process under the condition of higher irrigation amount. Achieve carbon sequestration and emission reduction and water utilization system promotion. Considering net ecosystem productivity and carbon emission efficiency of farmland, SW3 treatment can be used as a farmland management mode for water saving, emission reduction and yield increase.