Soil organic matter, greenhouse gas emissions, and sorghum yield in semi-arid drylands

Abstract

Sorghum [Sorghum bicolor (L.) Moench] serves as a low-cost alternative to corn (Zea mays L.) in semi-arid regions of the world because of its high N and water use efficiencies. However, there has been a concern regarding N loss to the atmosphere as nitrous oxide (N2O) from semi-arid drylands. This study investigated various soil C and N components, including CO2 and N2O emissions, and crop yield with a dairy compost (13.5 Mg ha−1) and four rates of chemical N fertilizer (0, 22.4, 44.8, and 67.3 kg ha−1) in dryland sorghum. There was no significant difference in soil C and N fractions among N fertilizer rates, although compost addition numerically increased soil C storage and 67.3 kg ha−1 N rate resulted the highest yield in both years. Potential nitrogen mineralization (PNM) was negatively related to crop yield and positively related to grain N content. Soils with greater inorganic N and PNM had a lower carbon dioxide (CO2) emissions, while soils with greater potential C mineralization (PCM) had lower N2O emissions. The results of this study show no significant improvements in yield of dryland sorghum in the semi-arid environment of southern Great Plains in the short term. However, compost and 44.8 kg N ha−1 applications appeared to be beneficial when both yield and quality were compared.