Soil chemical and biological properties affected by 21-year application of composted manure with chemical fertilizers in a Chinese Mollisol

Li, X. H., Han, X. Z., Li, H. B., Song, C., Yan, J. and Lang. Y. 2012. Soil chemical and biological properties affected by 21-year application of composted manure with chemical fertilizers in a Chinese Mollisol. Can. J. Soil Sci. 92: 419-428. The effects of 21-yr of application of chemical fertilizers, composted pig manure (CPM) alone, and chemical fertilizers combined with compost on soil chemical and biological properties were investigated. Soil samples (0-20cm) were collected from a long-term fertilization experiment under corn (Zea mays L.) production in 2006, prior to seeding, at the corn tasseling stage and following harvest. Fertilizer treatments were: no fertilizer (CK), nitrogen fertilizer alone (N), N+ phosphorus (NP), N + P + potassium (NPK), CPM, N+CPM, N + P+CPM (NP+CPM), and N+P+K +CPM (NPK + CPM). Long-term application of N alone resulted in a reduction of soil pH by 0.38 units and reduced the available P concentration compared with CK. An increase in soil pH was seen with CPM alone and NPK +CPM. Both fertilizers sources, singly and combined, increased the total N and available N concentrations. Total P and total K concentrations were greatest with the NPK +CPM treatment. All fertilizer treatments increased the soil organic carbon (SOC), light fraction organic carbon (LFOC) and microbial biomass carbon (M BC) concentrations significantly (P <0.05) at the tasseling stage. The NPK +CPM treatment showed the greatest increase in SOC (12%), LFOC (78%) and M BC (44%) concentrations, compared with CK. Soil enzyme activities (invertase, urease, acid and alkaline phosphatases) tended to be greater at tasseling than other sampling dates, with highest enzyme activities in the NPK +CPM treatments. These findings suggest that a long-term application of CPM combined with NPK is an efficient strategy to maintain or increase soil quality in Mollisols for sustainable agriculture.