The Neutral Effect of Plastic Film Mulch on the Size of Soil Organic Carbon Pool.

Title: The neutral effect of plastic film mulch on the size of soil organic carbon pool Presentation author: Xiao Gang Li Affiliation: State Key Laboratory of Grassland and Agro-ecosystems, Institute of Arid Agroecology, School of Life Sciences, Lanzhou University. 222 South Tianshui Road, Lanzhou 730000, China. Abstract: Plastic-film mulch is widely used to increase soil temperature and reduce water evaporation in vegetable production. In China, it is also extensively used for growing grain crops, especially in temperature and rainfall limited areas. However, it remains unclear whether the technology changes soil organic carbon (SOC) balance. We assessed plastic-film mulch effects on SOC mineralization, input, and content in ridge-furrow prepared maize (Zea mays L.) croplands. Plastic-film effects in increasing soil temperature and moisture principally happed in the early growth of maize. We found that plastic-film mulch increased SOC mineralization, as evidenced by the increased decomposition of buried maize straw and marginal reduction in the light SOC content compared with no mulch treatments. The increased SOC mineralization in mulched soils can be also supported by the stimulated soil nitrogen mineralization compared with non-mulched soils. Plastic-film mulch significantly increased root-derived carbon input, as indicated by the augmented root biomass production proportionately to the increased maize grain yield, compared with no mulch treatments. Up to 6 years¡¯ continuous experiment implementation, total SOC concentration and stock in the 0¨C0.15 m soil layer did not change relative to no mulch. We conclude that the increase in soil temperature and moisture by use of plastic-film mulch enhances productivity, but importantly maintains the SOC level in temperature- and rainfall-limited semiarid regions by balancing the increased SOC mineralization with increased root-derived C input. Key words: Maize; Root biomass; Soil carbon mineralization; Soil organic carbon level; Soil warming.