Prof. Bingzi Zhao1, Dr. Zengqiang Li1, Prof. Daniel C. Olk2, Prof. Zhongjun Jia1, Prof. Jiabao Zhang1
1Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China, 2USDA-ARS, National Laboratory for Agriculture and the Environment, 1015 N. University Blvd., Ames, IA 50011, USA, , USA
Soil microorganisms are considered the most effective decomposers of applied crop residues, but it is poorly understood which communities are primarily responsible for decomposition under different conditions. A pot experiment was conducted in a greenhouse to follow the cycling of C and N derived from maize (Zea mays L.) residues labeled with both 13C and 15N to a subsequent winter wheat (Triticum aestivum L.) crop and to soil pools under planting with winter wheat (+P) or an unplanted control (–P), both in soil maintained at field moisture capacities of 40% and 80%. Soil microbes involved in residue decomposition were investigated by 13C phospholipid fatty acid (13C-PLFA) analysis technique. At wheat maturity, a total of 68% of residue N was recovered in the +P treatments, in which 26% was recovered from wheat plants and another 42% from soil total N (TN), independent of the water regimes, while only 50% was recovered from TN in the –P treatments. More residue C was recovered as soil organic carbon in +P than –P treatments (33% vs. 27%), and the trend became more significant with soil moisture. In addition, the +P soil had 35–48% larger microbial biomass carbon (MBC) than the –P soil, and more residue C was recovered as MBC in +P than –P treatments (7% vs. 4%), suggesting the induced microbial utilization of the applied residues. The distribution of the residue-derived PLFA-C showed that only 16:1ω7c and 18:1ω7c had larger relative abundances in the +P than the –P soils, suggesting that they were mainly stimulated by the presence of wheat. Our results demonstrate that the enhanced recovery of residue-C and -N by the presence of wheat plants was mainly from the induced microbial utilization of applied residues by altering the activities of specific microorganisms.
Dr. Bingzi Zhao is a Professor in the Institute of Soil Science, Chinese Academy of Sciences. Her research has focused on the crop straw decomposition, dynamic release of straw-derived C, N, P, and K, and their contributions in the plant-soil system. She has also worked on the linkage between chemical structure of soil organic matter and microbial community composition. Her current interest in soil organic matter research is how to improve soil quality of various degraded soils by crop straw application.
Poster: Contributions of residue-C/-N to plant growth and SOM pools under planted and unplanted conditions