长期保护性耕作对黄土高原旱地土壤养分和作物产量的影响

Long-term effects of tillage system on soil nutrients and grain yields in rainfed area of Loess Plateau

通过长期定位试验,研究了黄土高原西部旱农区传统耕作措施（T）和5种保护性耕作措施免耕＋秸秆覆盖（NTS）、免耕（NT）、传统耕作＋秸秆还田（TS）、传统耕作＋地膜覆盖（TP）和免耕＋地膜覆盖（NTP）对土壤有机质、速效养分以及作物产量的影响。结果表明,经过6 a不同耕作措施后,各处理土壤有机C、NO3-N以及速效P含量均有所提高,其中有机C含量比试验初期提高了4.92%～18.05%,NO3-N含量提高了17.98%～31.08%,速效P含量提高143.04%～212.87%。各处理土壤速效钾含量均有所下降,其中以NTS和TS降幅较小,仅为2.75%和6.26%。6 a间小麦和豌豆平均产量均以NTS最高（分别为2 030 kg.hm-2和1 381 kg.hm-2）,而NT最低（1 608kg.hm-2和1 060 kg.hm-2）。传统耕作秸秆还田能促进土壤耕层肥力的提高,但产量效应不明显;地膜覆盖有些年份增产效应明显,但不利于土壤肥力的持续提高。因此,在黄土高原西部旱农区实施免耕秸秆覆盖既有利于作物产量的提高,也可以改善耕层土壤肥力。

This study determined the long-term effects of tillage systems on soil nutrients and crop productivity in a semiarid environment .A long-term field study was initiated at Dingxi , the western Loess Plateau of China , in 2001 . Field pea （ Pisum sativum L .） in rotation with spring wheat （ Triticum aestivum L .） were grown under six tillage sys-tems ：conventional tillage （T ） , conventional tillage with stubble incorporating （TS ） , no-till with no stubble retention （NT） ,no-till with stubble retention （NTS） ,conventional tillage with plastic film mulching （TP） ,and no-till with plas-tic mulching （NTP） .The results showed that ,compared with the pretreatment ,six tillage systems increased soil organic carbon by 4 .92% ~18 .05% ,available N by 17 .98% ~31 .08% ,available P by 143 .04% ~212 .87% .However , compared with the pretreatment ,six tillage systems decreased available K by 2 .75% and 6 .26% under NTS and TS ,re-spectively .The average grain yields in a six-years term were highest under NTS with stubble retention for both spring wheat and field pea（2 030 vs .1 381 kg·hm-2 ） ,and lowest under NT without stubble retention for both spring wheat and field pea （1 608 vs .1 060 kg · hm-2 ） .Conventional tillage with stubble incorporating could improve soil fertility , but this practice could not increase grain yield .The plastic mulch could increase grain yield in some seasons ,but this practice could not sustainably improve soil fertility .Therefore ,no-till with stubble retention is the most promising system for increasing grain yield and improving the sustainable development of agriculture in the semiarid Northwest China .