不同还田方式对玉米秸秆腐解及土壤养分含量的影响

通过土壤耕作和秸秆还田试验，以玉米秸秆为研究对象，探讨东北棕壤土区适宜的秸秆还田方式，为秸秆资源的高效利用提供理论依据。在辽宁沈阳设置连续两年（2014-2015年）的田间定位试验，采用尼龙网袋法研究免耕覆盖（NTS）、旋耕还田（RTS）和翻耕还田（PTS）3种秸秆还田方式下秸秆腐解率和碳氮磷钾养分释放率，分析秸秆还田方式对耕层土壤养分含量的影响。结果表明，RTS和PTS秸秆腐解速率均表现为前期快、后期慢，秸秆养分释放率均表现为钾 > 磷 > 碳 > 氮。NTS、RTS和PTS处理秸秆两年平均腐解率分别为38.8%、78.0%、65.9%，两年平均碳释放率分别为56.5%、78.8%、69.4%，氮释放率为16.7%、53.5%、38.8%，磷释放率为81.3%、92.5%、89.8%，钾释放率为92.0%、99.4%、98.9%。NTS处理秸秆腐解率及碳氮释放率与还田时间符合逻辑斯蒂曲线方程，RTS和PTS处理秸秆腐解率、碳氮释放率及3种还田方式秸秆磷钾释放率随还田时间变化符合米氏方程。秸秆还田有助于提高耕层土壤有机碳和全氮含量，RTS处理土壤全磷含量显著高于PTS处理（P<0.05），与NTS处理全磷含量差异不显著，3种还田方式土壤全钾含量差异不显著。综合分析秸秆腐解和耕层土壤培肥效果，东北棕壤土区建议玉米秸秆还田方式为旋耕秸秆还田。

Effect of straw return methods on maize straw decomposition and soil nutrients contents

By investigating the impacts of tillage and straw return methods on maize straw decomposition, a suitable approach of returning maize straw to soil was explored for straw utilization with high soil efficiency in the brown soil area of northeastern China. A two-year (2014-2015) field experiment including no-tillage with straw mulch (NTS), straw incorporation through rotary tillage (RTS) and straw incorporation through plow tillage (PTS) treatments was conducted in Shenyang, Liaoning Province. Nylon bags containing straw 2-5 cm long were buried in different depths of soil according to tillage depth of different treatments (0 cm for NTS, 15 cm for RTS and 25 cm for PTS) in the study, and the decomposition of straws and release rates of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) by maize straw, along with the effects of straw return on nutrients contents of the topsoil were tested. The results showed that straw decomposition rates were high at the early phase and slowed down at the later phase under both RTS and PTS treatments, with the order of nutrients release rates in all treatments of K > P > C > N. The mean decomposition rates of straw in both years were 38.8%, 78.0% and 65.9% respectively for NTS, RTS and PTS treatments. Nutrients release rates of returned straws under NTS, RTS and PTS treatments were respectively 56.5%, 78.8% and 69.4% for C, 16.7%, 53.5% and 38.8% for N, 81.3%, 92.5% and 89.8% for P, and 92.0%, 99.4% and 98.9% for K. The tendency for straw decomposition and C and N release under NTS treatment fitted well with Logistic function, but those of RTS and PTS treatments fitted Michaelis-Menten function. Moreover, K and P nutrients release of all the three treatments changed according to the Michaelis-Menten functions. Straw return enhanced organic carbon and total nitrogen contents of the topsoil. Then total soil P content of RTS treatment was significantly higher than that of PTS (P < 0.05). However, there was no significant difference in total soil P content between RTS and NTS treatments, and in total soil K content for all the treatments. Based on comprehensive analysis from straw decomposition characteristics and fertility, straw incorporation through rotary tillage was the suitable approach for maize straw return in brown soil areas in Northeast China.