耕作措施对华北夏玉米田土壤温度和酶活性的影响

为探讨长期耕作措施下华北平原夏玉米生长季土壤温度与酶活性的变化规律，本研究对四种耕作处理（免耕秸秆还田NTS，旋耕秸秆还田RTS，翻耕秸秆还田CTS和翻耕秸秆不还田CT）下土壤层次的温度和酶活性进行了测定和分析。结果表明：同一土壤层次的各耕作处理均从6：00．18：00呈现正弦波的变化特征；免耕、旋耕等保护性耕作处理在玉米的生育期内温度变化平稳，日均差均小于翻耕秸秆还田和翻耕秸秆不还田；免耕秸秆还田处理土壤酶活性最高，脲酶活性在夏玉米的3个生育期（播种期、大喇叭口期和收获期）分别高于翻耕秸秆不还田处理28．98％，35．62％和24．9％，碱性磷酸酶分别高32．7％，11．94％和10．39％，脱氢酶分别高27．53％，20．39％和30．53％，旋耕和翻耕秸秆还田处理3种酶的活性也明显高于翻耕秸秆不还田处理；旋耕与翻耕秸秆还田处理脲酶和碱性磷酸酶的差异不显著，脱氢酶的差异达到了5％的差异显著水平；通过研究表明在华北平原采用少免耕为主的保护性耕作措施，可以提高土壤酶活性，降低成本，提高经济效益。

Soil temperature dynamics and enzyme activities as influenced by tillage in north China

This study intends to investigate soil temperature dynamics and enzyme activities under different tillage treatment systems in North China. The experiment has four tillage treatments： no-tillage with straw retention （NTS）, rotary tillage with straw retention （RTS）, conventional tillage with straw retention （CTS）, and conventional tillage without straw （CT）. Soil temperature and enzyme activity were monitored in corn growing season. Soil temperature displayed a sinusoidal variation from 6 am to 18 pm. The soil temperature waves of NTS and RTS fluctuated moderately. At sowing stage, flare opening stage, and harvest stage, urease activity under NTS was 28.98%, 35.62% and 24.9% higher than that under CT; alkaline phosphates under NTS was 32.7%, 11.94%, and 10.39% higher than that under CT; and dehydrogenase content under NTS was 27.53%, 20.39% and 30.53% higher than that under CT. The treatments of RTS and CTS also had higher amount of soil enzymes than the CT treatment, There were no significant dif- ferences in urease and alkaline phosphates between CTS and RTS treatments. However, the content of dehydrogenase differed sig- nificantly （at P〈0.05） between the CTS and RTS treatments. Our results suggest that conservation tillage has the advantages of im- proving soil enzyme activity, reducing costs, and bringing about ecological benefits in the North China Plain..