Effects of combined application of swine manure compost fermented by different methods with chemical fertilizer on soil physicochemical properties and NH₃ volatilization of summer maize

This study investigated the effects of swine manure composts from different fermentation methods combined with chemical fertilizers on summer maize yield, fertilizer use rate, soil physicochemical properties, aggregate stability, enzymes activities, and NH₃ volatilization loss, with the aim of providing theoretical support for rational fertilization and soil fertility improvement in maize fields of the North China Plain. In 2023, a field experiment using swine manure composts fermented with different methods combined with chemical fertilizers (organic fertilizer∶chemical fertilizer = 25%∶75%) was conducted in maize field at the Science & Education Park of the Henan Agricultural University in Yuanyang County, Henan Province. Six treatments were established: no fertiliztion (CK), single application of chemical fertilizer (T1), natural composting + chemical fertilizer (T2), water-regulated trough composting + chemical fertilizer (T3), acid-regulated trough composting + chemical fertilizer (T4), and trough composting + chemical fertilizer (T5). Soil samples from 0−20 cm depth were collected at five growth stages of maize: pre-sowing, jointing, bell mouth, filling, and maturity. The analysed indexes included soil pH, contents of ammonium N, nitrate N, available P, available K, organic matter, as well as soil bulk density, enzymes (urease, acid phosphatase, and dehydrogenase) activities, aggregate distribution characterstics and C/N ratio, and NH₃ flux dynamics. Maize yield and fertilizer use rate were determined at maturity. The results showed that, compared with CK and T1, compost-chemical fertilizer combinations increased maize yield, with T4 showing the highest yield (39.90% and 15.71% increase, respectively). All compost treatments enhanced soil available nutrients and organic matter contents while reducing pH and bulk density, with T4 exhibiting optimal effects. Compared to T1, T4 increased 0.25−2 mm and ≥2 mm aggregates proportions by 45.40% and 67.11%, respectively, with 26.47% higher aggregate C/N ratio at maturity. Soil enzymes activities peaked in T4, showing 26.77%, 24.89%, and 26.15% increases in urease, acid phosphatase and dehydrogenase activities versus T1. Compost treatments reduced the peak NH₃ flux and cumulative emissions, with T4 showing the maximum reduction (29.66% and 40.18% lower than T1). T4 improved N, P, and K use rates by 17.28%, 56.64%, and 25.19%, respectively, compared with T1. In conclusion, application of acid-regulated trough compost combined with chemical fertilizers at a 25∶75 ratio effectively enhanced maize productivity, soil nutrients contents, aggregates structure and C/N ratio, and enzymes activities. It also reduced N loss and improved fertilizer use rate. The results provide both theoretical and practical guidance for sustainable intensification of cropland in the North China Plain.