Abstract:
Objective This study was to investigate the effects of chemical fertilizer combined with different types of organic materials on soil properties, nitrogen transformations and related soil enzyme activities of tropical latosol, which would provide theoretical basis for improving soil productivity and developing rational nitrogen management strategies.
Methods Based on a field experiment, we collected soils treated with chemical fertilizer (N), chemical fertilizer plus straw (N + straw) and chemical fertilizer plus sheep manure (N + manure) for six years, and determined soil chemical properties, nitrogen transformation rates and related enzyme activities.
Results The organic material amendment increased soil organic carbon (SOC), soil total nitrogen (TN) and pH by 7.43%-40.28%, 28.57%-42.86% and 1.60%-52.05%, respectively, and decreased soil C/N values by 1.44%-15.35%, compared with the CK treatment, with greater effect under sheep manure application. Soil net N mineralization rate, potential ammonia oxidation, net nitrification rate and potential denitrification rate were increased by 3.00, 11.48, 0.28 and 4.07 times, respectively, when organic materials were continuously incorporated. The amendment of organic material significantly increased the activities of soil urease, nitrate reductase, nitrite reductase and β-1,4-glucosidase, but significantly decreased the activities of nitrite oxidase and polyphenol oxidase. Nitrogen transformations rates (except net nitrification rate) were significantly and positively correlated with SOC, TN, pH and activities of urease, nitrite reductase and nitrate reductase, but had significantly negative correlation with polyphenol oxidase activities.
Conclusion Chemical fertilizer co-applied with organic material can improve the soil properties and promote nitrogen transformations of tropical latosol, with greater effect under sheep manure application. Therefore, chemical fertilizer combined with sheep manure is an effective measure to improve soil properties and enhance nitrogen availability of tropical latosol.