Prof. Xueyun Yang1, Mr Renjie Wang1, Prof. Shulan Zhang1
1Northwest A&f University, Yangling, China
Understanding the mechanism of soil organic matter (SOM) sequestration under long-term fertilization is of great importance in sustaining crop productivity and mitigating climate change. We examined the responses of total SOM, mineral-associated OM, particulate OM (POM) and its light (Light-POM) and heavy fractions (Heavy-POM) to the application of synthetic fertilizers (nitrogen and phosphorus, NP) and their combinations with organic manure (MNP/K) in four long-term trials under rain-fed cropping system in the Loess Plateau. Long-term fertilization significantly increased SOC and total N (TN) storages, the sequestration rates of SOC and TN were, on average, 121 and 13 kg ha-1 y-1 under NP and 372 and 39 kg ha-1 y-1 under MNP/K, respectively. The sequestered SOM was generally distributed more in the mineral-associated OM pool than in the POM pool in NP treatment. However, the POM pool had more sequestration of SOM than mineral-associated OM pool did under MNP/K treatment. In addition, Light-POM pool was more sensitive to sequester OM than Heavy-POM pool and contributed large proportion to the total OM sequestration in POM pool. The different roles of the SOM pools in sequestration of OM are possibly related to the saturation degree of SOM, which manifested by significantly lowering proportion of mineral-associated OM pool and raising of POM pool, especially Light-POM pool under the application of MNP/K. We concluded that SOM sequestration was mainly contributed by sequestering more carbon in stable pool under application of synthetic fertilizers, but in labile pools under application of synthetic fertilizers plus manure in long-term.
Xueyun Yang, born in 1967 in Ningxia province, China. He has been working on long-term nutrient management of grain crops (wheat and maize) for 20 more years. Currently he holds a professor position at College of Natural Resources and Environment, Northwest A&F University, China. His research is focusing on crop productivity, soil fertility, nutrient use efficiency and environmental consequences.