Assessment of fertility quality of black soil based on principal component and cluster analysis

Objectives Based on long-term experiment on black soil fertility and fertilizer efficiency (Gongzhuling), a field experiment was conducted to assess the effects of different fertilization measures on the qualities of soil fertility, so as to provide scientific references for establishing the optimal fertilization pattern in the northeast black soil region of China.

Methods By means of principal component and cluster analysis, differences of soil fertility quality were assessed under long-term fertilization comprehensively, soil fertility difference on different fertilization was developed using Euclidean distance method and single linkage cluster.

Results Maize yields were positively and significantly correlated with soil enzyme activity, the contents of total N, P and K, available N, P and K, soil organic matter, soil microbial carbon and nitrogen (P < 0.05, P < 0.01), negatively correlated with soil pH, not significantly correlated with soil nitrate N and ammonium N. The soil fertility qualities were in order of 1.5 (NPK + M1) > NPK + M2 > NPK + M1 > NPK + M1(R) > NPK + S > NPK > CK, whereas R was rotation of corn with soybean. The soil fertility quality was clustered into four classes, the fertility quality in 1.5 (NPK + M1) and CK were respectively clustered into the best (first-class) and the worst (fourth-class) one, and those in treatments of NPK + M2, NPK + M1, NPK + M1 (R) were clustered into the second-class, those in NPK + S and NPK treatments were clustered into the third-class.

Conclusions The soil fertility qualities are in descended order of chemical fertilizers combined with manures, NPK fertilizer combined with straw returning, single NPK fertilizers and CK. Therefore, mixed application of chemical fertilizers with organic fertilizers should be promoted for the improvement of soil fertility quality and the everlasting use of farmland.