Effects of swine slurry application on ammonia emission, nitrogen utilization and apparent balance of a winter wheat-summer maize rotation system

With the development of intensive swine production in China, large amounts of slurry are produced, which causes nitrogen and phosphorus loss and serious non-point pollution. A potentially efficient way to solve these environmental problems is to substitute mineral fertilizer with swine slurry in intensive maize (Zea mays L.)-wheat (Triticum aestivum L.) double-cropping rotation systems, which could promote the development of sustainable agriculture and animal husbandry. A field experiment was performed with swine slurry application in a maize-wheat double-cropping rotation system in the North China Plain. The study included the following seven treatments with three replications:zero-N control (CK); urea broadcast (CK1); urea injection (CK2); swine slurry as a substitute for 25% urea-N broadcast (25%WB), 50% urea-N broadcast (50%WB), 25% urea-N injection (25%WI), and 50% urea-N injection (50%WI). Swine slurry was applied to the soil before maize and wheat seeding. Compared with the CK, the application of urea and swine slurry significantly improved maize and wheat grain yield and N uptake, with the greatest effect seen in the 25%WI, followed by the 50%WI. Compared with the CK1, the N agronomic efficiency, N partial productivity, and apparent N recovery rate under treatments of urea injection and swine slurry broadcast and injection were significantly improved. The greatest improvement was seen in treatments of swine slurry injection, followed by treatments of swine slurry broadcast, but no significant difference was found between the 25%WI and 50%WI treatments. Compared with CK, the application of urea and swine slurry significantly improved nitrate accumulation. The increase in inorganic nitrogen ranged from 50.8%-87.9% throughout the 0-100 cm soil profile after maize harvest. No significant difference in nitrate accumulation was found among the 50%WB, 25%WI, and 50%WI treatments. Compared with CK1, swine slurry broadcast and urea and swine slurry injection significantly reduced the total amount of ammonia loss during the seeding period of maize and wheat, with reductions ranging from 26.5% to 48.6% and 11.4% to 29.1%, respectively. Meanwhile, swine slurry broadcast and injection significantly reduced N surplus from 7.6% to 16.0%, with the biggest difference found in the 25%WI treatments. However, no significant difference was found between the 25%WI and 50%WI treatments. In view of the yield, nitrogen utilization, and environmental benefits, swine slurry as a substitute for 25% and 50% urea-N injection were reasonable methods of swine slurry application in the intensive summer maize-winter wheat double-cropping rotation field.