Effects of conservation tillage and wheat cultivation of paddy field on soil nutrients

Effects of conservation tillage and wheat cultivation on soil nutrients in paddy rice cultivation after ten years were investigated. Four treatments, disk till-fallow(DTF), disk till-wheat(DTW), conservation till-fallow (CTF) and conservation till-wheat (CTW) were used. Results show that soil total N in CTW is 10.03%, 26.81% and 23.17% greater than that in DTF, DTW and CTF, respectively. Soil available N also presents the same trend to that of total N. Soil total P in CTW is 12.93%, 15.86% and 21.36% greater than that in DTF, DTW and CTF, respectively. At 0～10 cm depth, soil available P content in CTW is as 4.5 and 2.1 times as that in DTF and DTW, respectively. Soil total K presents the similar trends to that of total N and P. In contrast to DTF, the contents of Ca₂-P, Ca₈-P, Al-P, Fe-P, O-P and Ca₁₀-P in CTW are rapidly increased. The decreases in quantity of exchangeable, easily reducible binding, carbonate binding and organic matter-bound and amorphous Fe, Mn and Cu in CTW are observed, while the increases in residual Fe, Mn and Cu. The accumulations of exchangeable Zn and easily reducible Mn-binding Zn are increased in CTW, though the contents of amorphous Zn and organic matter-bound Zn are decreased significantly. Moreover, the availability of Fe, Cu and Mn is reduced, while that of Zn increased. In paddy rice cultivation, conservation tillage and wheat cultivation could not only increase the content of soil nutrients at the topsoil, but also alleviate harm of Fe and Mn on crops by influencing the forms soil P, Fe, Mn, Zn and Cu forms.