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Cropland age from grassland conversion to cropland affects nitrous oxide emissions
- Jiao, Yan, JianHua, Hou, JiangHong, Zhao, WenZhu, Yang
- Acta agriculturæ Scandinavica 2015 v.65 no.6 pp. 566-574
- ammonium nitrogen, cropland, ecosystems, ecotones, emissions, grasslands, growing season, land use, nitrous oxide, soil water content, China
- The effects of soil properties and cropland age on atmospheric nitrous oxide (N ₂O) emissions following the conversion of grassland to cropland in temperate grassland ecosystems are uncertain. In this study, N ₂O emissions were compared among grassland and cropland soils in the agro-pastoral ecotone of Inner Mongolia over three growing seasons. Four adjacent sites with different land-use histories were selected, including grassland and croplands cultivated for 5, 10, and 50 years after conversion. N ₂O flux measurements were obtained using a closed-chamber method and were performed continuously during vegetation periods. After the conversion of grassland to cropland, N ₂O emission initially decreased and thereafter increased in the study sites. The cumulative N ₂O emissions of the cropland soils 5 and 10 years in age were 10–50% less than those of the grassland, and the N ₂O emissions from the cropland soil 50 years in age were 10–30% greater than the grassland. When the seasonal emissions were correlated against single soil parameter, the key soil parameter that affected N ₂O emissions over the entire growing season was the soil moisture content. When the interactions among soil parameters were considered, the amount of N ₂O emissions could be quantitatively described by a linear combination of two soil variables, the soil ammonium nitrogen (NH ₄⁺-N) and moisture concentrations. This study demonstrates how the time of land use conversion from grassland to cropland can positively or negatively affect N ₂O emission.