Manure replacement of chemical fertilizers can improve soil quality in the wheat-maize system

Organic fertilizer application has been proved to improve soil fertility, but it is not yet known whether organic fertilizers can improve soil quality and maintain soil health. Here, we explored the influence of manure replacing chemical fertilizers on soil quality by measuring soil nutrients, enzyme activity, and microbial abundance. We set up four fertilization treatments: unfertilized control (CK), 100 % fertilizers containing nitrogen (wheat, 157.5 kg ha−1; maize, 178.5 kg ha−1), phosphorus and potassium (NPK), 50 % fertilizers containing nitrogen (wheat, 78.75 kg ha−1; maize, 89.3 kg ha−1), phosphorus and potassium +50 % manure (wheat, 78.75 kg ha−1; maize, 89.3 kg ha−1) (NPKM), and 100 % manure (wheat, 157.5 kg ha−1; maize, 178.5 kg ha−1) (M). This paper focused on the calculation of the weights of 18 soil biotic and abiotic indicators by principal components analysis (PCA), and the calculation of soil quality by Total Data Set. Results showed that compared to NPK and CK, M increased soil organic carbon, total nitrogen and dissolved organic carbon at the wheat filling stage (p < 0.05), while it increased soil available phosphorus, dissolved organic carbon, total nitrogen, ammonium nitrogen, microbial biomass carbon, microbial biomass nitrogen and N-acquisition enzyme activity at the maize filling stage (p < 0.05). The soil quality index of M in the rhizosphere and bulk soils was 48.7 %–78.0 % (p < 0.05) and 50.0 %–74.7 % (p < 0.05) higher than those of CK at the wheat and maize filling stages, respectively. Our findings suggested that complete replacement of chemical fertilizers with organic manure increased soil quality by enhanced soil biotic and abiotic factors in the wheat-maize rotation system. In the future, the use of organic fertilizers should be appropriately increased in the management of the fields to maintain soil health and adhere to the sustainable development of agriculture.