Effect of long-term conservation tillage on soil fertility in rain-fed areas of the Loess Plateau

Based on long-term field experiments in Dingxi, west of the Loess Plateau, the effects of conventional tillage (T) and 5 conservation agricultural patterns conventional tillage with stubble incorporation (TS), no-till and no-stubble retention (NT), no-till with stubble retention (NTS), conventional tillage with plastic mulching (TP) and no-till with plastic mulching (NTP) on the quality of soil fertility were studied for the rotation systems of pea-wheat (P→W) and wheat-pea (W→P) under rain-fed farming. The results show that soil fertility is improved by the two stubble retention systems, TS and NTS. Soil organic matter, total N, P and K, and available P and K under TS and NTS are much higher than those under T with respective increasing ranges of 11.61%~12.21% and 12.13%~16.99%, 7.29%~8.42% and 11.58%~12.95%, 10.35%~14.63% and 13.79%~18.29%, 7.32%~7.51% and 8.78%~9.15%, 11.10%~12.41% and 16.29%~20.99%, and 25.11%~43.26% and 31.62%~44.22%. On the contrary, soil pH under TS and NTS are lower than that under T with respective decreasing ranges of 0.11~0.17 and 0.09~0.16. Using addition/multiplication and weighted integrated methods, quantitative assessments of the quality of soil fertility in different tillage systems was performed. The order of the quality of soil fertility index ranked from high to low is NTS, TS, NTP, NT, T and TP for P→W rotation; and is NTS, TS, NT, NTP, TP and T for W→P rotation. This indicates that no-till with stubble retention replenishes soil nutrient pool and improves the quality of soil fertility in rain-fed areas of the Loess Plateau.