Evaluation on the sustainability of cropland under different long-term fertilization in Eum-Orthic Anthrosols area

【Objectives】Fertilization is one of the main approaches to increase crop yields and soil fertility. Assessment on the sustainability of farmland under long-term different fertilization modes will supply theoretical and practical supports for rational and sustainable fertilization in areas of Earth-Orthic Anthrosols. 【Methods】Based on a long-term experiment of National Monitoring Base of Soil Fertility and Fertilizer Efficiency on Loess Soil in Yangling City, Shaanxi Province, samples were collected from the 9 treatment plots (CK, N, NK, PK, NP, NPK, SNPK, M1NPK and M2NPK), and totally 22 parameters were analyzed for the calculation of soil nutrient index (NI), microbial index (MI), crop index (CI) and sustainability index (SI), which were used to comprehensively assess the sustainability of the soil-crop system under different fertilization modes. 【Results】1) The soil NI values in both the CK and N treatments were respective 0.75 and 0.87, lower than the threshold (1.00), and there was significant different between them (P 0.05). While those in other treatments were in range of 1.12-3.12, higher than the threshold. The differences between NP and NK and between SNPK and PK were not significant, but significant among other treatments (P0.05). 2) The soil MI values in chemical fertilizer treatments (CK, N, NK and PK) were all lower than the threshold (1.00) in range of 0.74-0.84. The differences between NP and NK and between SNPK and PK were not significant, whereas significant between these two groups (P0.05). The MI values in treatments containing NP (NP, NPK, SNPK, M1NPK and M2NPK) were in range of 0.98-1.21, all close to or higher than the threshold 1.00. The difference was not significant between M1NPK and M2NPK, nor between NP, NPK and SNPK, but significant between these 2 groups (P0.05). 3) The CI values in CK, N, NK and PK were in range of 0.52-0.60, all lower than the threshold 1.00. Significant difference was only between N and PK (P 0.05). The CI values in treatments containing NP were in range of 0.98-1.02, all close to or higher than the threshold, and there were not significant differences among them. 4) The SI values in CK, N, NK and PK were 0.49, 0.54, 0.74 and 0.99 respectively, all lower than the threshold (1.30). The SI values in NP and NPK were respective 1.18 and 1.26, close to the threshold, and there was no significant difference between the two treatments. The SI values in the combination treatments of chemical and organic fertilizers (SNPK, M1NPK and M2NPK) were respectively 1.55, 2.32 and 2.94, and were 19.5%, 78.8% and 126.3% higher than the threshold, and significantly different among them (P0.05). 5) The variability was 50.2%, 29.1% and 18.4% in NI, CI and MI. The variability SI, computed by NI, CI and MI, was 62.1%. 【Conclusions】 In winter wheat-summer maize rotation system, the soil fertility is unsustainable under long-term no fertilization or partial fertilization patterns, basically sustainable under balanced chemical fertilization (NP and NPK) patterns, and the most sustainable under the chemical NPK fertilizer and straw return (SNPK), or manure (M1NPK) combination in areas of Eum-Orthic Anthrosols.