黄土高原旱地土壤质量评价指标研究

基于设置在陇中黄土高原半干旱区的长期定位试验,运用综合评价模型,定量评价了小麦→豌豆双序列轮作系统6种不同耕作方式对土壤质量的影响。结果表明,采用加权综合法和加乘法则对土壤质量进行综合评价,能够较好地反映土壤质量的实际情况,敏感地反映耕作方式对土壤质量的影响。运用逐步判别分析法对6种不同耕作方式传统耕作(T)、免耕作(NT)、传统耕作秸秆还田(TS)、免耕秸秆覆盖(NTS)、传统耕作地膜覆盖(TP)、免耕地膜覆盖(NTP)]下29项土壤属性指标进行筛选,建立了包括团粒结构、全氮、速效氮、有机质、蔗糖酶活性、作物产量、种植纯收益和产投比8项因子的简化评价指标体系。原始评价指标体系下2种轮作序列土壤质量指数排序均为NTSTSNTPNTTPT;简化评价指标体系下豌豆→小麦轮作序列土壤质量指数排序为NTSTSNTPNTTTP,而小麦→豌豆轮作序列土壤质量指数排序为NTSTSNTNTPTTP。进一步相关分析和方差分析表明,应用逐步判别分析法建立的简化指标体系具有较高的代表性,可适用于黄土高原半干旱区土壤质量评价。

Content of soil mineral nitrogen as influenced by sample extraction and preservation

Based on long-term field experiments at Dingxi in the western Loess Plateau,the effects of different agricultural meas-ures on soil quality were studied using an integrated assessment model.A total of 6 agricultural measures with 2 tillage systems and 3 ground-cover forms were used.The agricultural measured included conventional tillage(T),no-tillage(NT),conventional tillage with straw incorporation(TS),no-tillage with straw mulching(NTS),conventional tillage with plastic-film mulch(TP) and no-tillage with plastic-film mulch(NTP).The experiment was conducted in two rotation sequences.Sequence 1 started with pea followed by spring wheat(P→W) whereas sequence 2 started with spring wheat followed by field pea(W→P).The results showed that soil qual-ity evaluation with integrated-weighted and addition-multiplication methods reasonably reflected actual soil conditions,and the effect of tillage variations on soil quality.The 8 most sensitive indicators were selected from a total of 29 assessment indictors vial dis-criminative analysis.The selected indicators were used to evaluate soil physical quality,fertility,health and land productivity in the semi-arid areas of the Loess Plateau.These 8 indicators included soil aggregates,organic matter,total nitrogen,available nitrogen,invertase activity,grain yield,net income and output/input ratio.Based on the 29 indicators,the order of soil quality index(SQI) ranked from high to low was NTS,TS,NTP,NT,TP and T in both rotation sequences.Again based on the 8 indicators,the orders of SQI ranked from high to low were NTS,TS,NTP,NT,T and TP in the P→W rotation sequence,and NTS,TS,NT,NTP,T and TP in the W→P rotation sequence.The results of the 2 assessment systems were similar and highly correlated.This indicated that the 8 indicators were sufficiently representative of the soil conditions in the western Loess Plateau.