长期不同施肥下紫色土综合肥力演变及作物产量响应

为了综合评价长期不同施肥处理下紫色土肥力的变化趋势,寻求既能提高土壤肥力又能获得高产的紫色土科学施肥模式,该文以国家紫色土肥力与肥料效益监测基地长期定位试验数据为基础,运用内梅罗指数法对土壤综合肥力进行评价。结果表明,20 a间不同施肥处理土壤肥力发生了不同的变化趋势,长期不施肥(对照)与偏施化肥氮肥、氮钾肥土壤综合肥力指数(integrated fertility index,IFI)随着时间的推移逐渐下降,平衡施肥的氮磷钾、氮磷钾+牛粪、1.5倍氮磷钾+秸秆还田、氮磷钾+秸秆还田处理的IFI指数随着时间的变化有一定的波动,但相对于试验前都有不同程度的提高。各平衡施肥处理年均IFI值比对照分别提高34.5%,36.8%,52.3%,50.1%;通过IFI指数与各养分指标之间相关分析发现,土壤有机质、全磷、速效磷含量对紫色土土壤肥力的贡献较大;20 a产量变化趋势表明,平衡施肥产量明显高于偏施肥处理,其中长期秸秆还田配施NPK肥,增产效果最佳;相对产量与IFI指数呈S型曲线关系,紫色土IFI指数维持在1.63~2.01之间,可以实现相对最高产量;作物产量与土壤综合肥力指数二者之间呈显著的线性正相关关系,应用改良的内梅罗指数法计算的综合肥力指数能较好地反映土壤肥力状况。长期平衡施肥可以提高作物产量和土壤肥力,其中氮磷钾化肥配合秸秆还田是维持土壤肥力、实现作物高产的最佳培肥方式。

Integrated soil fertility and yield response to long-term different fertilization in purple soil

Abstract: The Nemero index is widely used to assess integrated pollution or fertility index. This index is becoming one of the most common methods because it has higher accuracy and shows better correlation with crops yield than other evaluating methods. However, the Nemero index is less used to evaluate the trend of integrated soil fertility under long-term varied fertilization especially on purple soils. Based on a long-term field experiment in the national monitoring station of soil fertility and fertilizer efficiency on purple soils, evolution trends of integrated soil fertility under different fertilization treatments for 20 years was therefore evaluated by the Nemoro index. By doing so, the authors expected to find out a sustainable fertilization management for high crop yield and soil fertility on purple soils. Results showed that different fertilization treatments had led to different trends of soil fertility after 20 years. Integrated fertility index (IFI) of soil with CK, N and NK treatments showed a declining trend over time. Whereas IFI of soil with NP, NPK, NPKM, 1.5NPKS and NPKS treatments were increased to a platform in 5 years and then kept stabilized after that. Balanced fertilization such as NPK, NPKM, NPKS, 1.5NPKS treatments resulted in high grain yield and their IFI had a small change with time. Furthermore, the average of IFI values for balanced fertilization treatments were significantly higher than that of CK and other partial fertilization treatments. Even so, the increased extents by these treatments were different. Averaged IFI values of soil with balanced fertilization treatments (NPK, NPKM, 1.5NPKS, NPKS) were 36.8%, 34.5%, 52.3%, and 50.1% higher than that of CK treatment, respectively. Correlations between IFI index and soil fertility parameters showed that soil organic matter, total phosphorus and available phosphorus content had more contribution to soil fertility of purple soil. In practice, result showed that fertilization could significantly improve the yield of crops compared to un-fertilization treatment (CK). Furthermore, grain yield with balanced fertilization was significantly higher than that with unbalanced fertilization treatments. The 20-year averaged grain yield of the fertilization treatment (NPKS, 1.5NPKS, NPKM, NPK, NK, NP, N) is 110.8%, 99.2%, 100.4%, 102.4%, 54.4%, 78.6%, and 36.5% higher than that of treatment without fertilization, respectively. Crop yield with NP treatment was higher than that with other partial fertilization treatments (NK, N) because purple soil can supply sufficient amount of K by continuous weathering of K-enriched mineral. Similarly, the integrated fertility index of soil under NP treatment was also higher than the other partial fertilization treatments. Although the IFI of soil with high rate of NPK fertilizer (1.5NPKS treatment) was the highest within all treatments, its averaged annual yield was even lower than that with less fertilizer treatments (NPKS). This indicated that excess fertilization might result in too high nutrient accumulation to cause yield reduction and reduce efficiency of fertilizer utilization. Based on 20-year data, NPK fertilization together with rice straw-return (NPKS) showed the best in term of crops yield and their stability. Regression between yield and IFI can be fitted significantly by a quadratic equation with a coefficient (R2) of 0.9758 (P<0.01). This showed that relative yield could reach the top when the integrated fertility index of purple soil was 1.81. This regression also indicated that IFI of purple soil should remain at a range of 1.63 to 2.01 for maximizing crop yield. In conclusion, long-term balanced fertilization can increase both crop yield and integrated soil fertility on purple soils and such trends could be matched well by the Nemoro index. Whereas, long-term unbalanced fertilization especially only N or NK application resulted in soil P deficiency, resulting in lower grain yield and a declining IFI. Furthermore, balanced NPK fertilization together with rice straw-return (NPKS) is recommended to maintain high soil fertility as same as rice yield on purple soils.