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(1 608 kg·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 systems: 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 plastic 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, respectively. 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.