Soil carbon and nitrogen dynamics in a Vertisol following 50 years of no-tillage, crop stubble retention and nitrogen fertilization

• Published in: Geoderma 2020-01, Vol.358, p.113996, Article 113996
• Main Authors: Jha, Pramod, Hati, K.M., Dalal, Ram C., Dang, Yash P., Kopittke, Peter M., Menzies, Neal W.
• Format: Article
• Language: English
• Subjects: Soil nitrogen; Soil organic carbon; Stubble management; Tillage
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2019.113996

•No tillage and N fertilization resulted in a buildup of C and N in soil.•Retention of stubble increased the total N concentration in soil.•Burning of stubble resulted in buildup of charcoal C and nitrate N in soil.•Retention of stubble increased stabilized C in soil.•Metabolic quotient was lower under the N fertilized and stubble retained treatment. Conservation agriculture commonly improves soil health and results in organic C sequestration. This study compared conventional tillage (CT) and no tillage (NT) systems, examining differences in stubble management [stubble burning (SB) and stubble retention (SR)] and N fertilization on soil C, C fractions and N. The experiment was established in 1968 on a Vertisol at Hermitage in Queensland, Australia. After 50 years of management; it was found that the tillage regime, the addition of N fertilizers, and the stubble management were all important in influencing soil C pools in 0–0.1 m of soil depth. Overall, the addition of N fertilizers and the tillage regime were the most important management factors. For example, the addition of N fertilizers at a rate of 90 kg ha−1 resulted in an average increase in SOC of 18%, while use of NT resulted in an average increase in SOC of 5%. Similarly, application of N fertilizers increased total soil N (TSN) concentrations by ≤25.5%, increased the stabilized SOC fraction by ≤26.6%, and increased microbial biomass C by ≤22%. Regardless, stubble management practices were also important, with the retention of stubble increasing TSN, increasing the stabilized C fraction, and increasing the microbial biomass C ≤ 30%. Finally, it was observed that the microbial metabolic quotient was 39% higher when stubble was burned and in the absence of N fertilization, indicating microbial stress under these treatments. The study clearly shows the importance of stubble retention and N fertilization in conservation agriculture for improvement in soil health and maintenance of soil C levels.