Abstract: Long-term field experiments on the responses of soil buck density and soil nutrient to tillage patterns in a rain-fed pea→wheat→pea rotation system were conducted in Dingxi, Gansu, China. The effects of conventional tillage (T) and three conservative agriculture patterns (conventional tillage with stubble incorporation, TS; no till with no stubble, NT; no till with stubble retention, NTS) were studied. The results showed that: the conservative tillage treatments significantly increased the contents of soil organic carbon, total N, total P, total K, available N、P and K, at the depth of 0-5 cm and the NTS had the optimal effect. The management of NTS decreased bulk density in each depth of 0-30 cm. There are significantly positive correlations between SOC, N and P. In short, 3 conservation tillage treatments can add the contents of the soil nutrients, but decrease the soil bulk density in comparison with T. Soil organic carbon and total nitrogen in pea field were respectively increased 10.52%, 4.63%, 4.83% and 13.83%, 7.45%, 8.51%, but soil bulk density decreased of 4.80%, 2.67%, 4.00%. In spring wheat field, soil organic carbon and total nitrogen respectively increased 11.99%, 7.78%, 12.10% and 11.11%, 6.67%, 3.33%, while soil bulk density was reduced of 4.62%, 3.08%, 4.62%. It is important that the conservation tillage treatments can improve soil structure and the capacity of maintaining fertility.

Key words: conservative tillage, soil buck density, soil nutrients, Loess Plateau