The Soil Respiration And Its Factors Under Different Tillages

Different tillages and planting patterns can significantly affect the biological,chemical and physical properties of soil.The study was conducted during a long term（since 2001）tillage field experiment at Dehui Experimental Station of the Northeast Institute of Geography and Agroecology,Chinese Academy of Sciences.The aims of this study were to evaluate the effect of soil carbon release on soil respiration rate,soil temperature,soil water content and soil microbial community under different tillages and planting patterns（no-tillage,Rotation）,and the combined effects of these factors on soil carbon release and yield under extreme drought events induced by climate change.The main findings are as follows:Effects of different tillages and planting patterns in normal years（1）Soil respiration showed significantly interannual and seasonal pattern under different tillage treatments and plantings.There was no significant difference between MP（mouldboard plough）and NT（no-tillage）with the soybean-maize rotation（CR）or mazie monoculture（CC）.But there were interannual and seasonal variations.The soil respiration rate of CR in July and August was lower than that in CC but no significant.（2）The effect of tillage treatments on soil water content varied.Compared with MP,NT significantly increased soil water content by 14.6% under monoculture maize during the growing season;while the increase under rotation was not significant.（3）The combined exponentiall model indicated model indicated that soil respiration had a positive correlation with respiration rate.（4）There was on significant difference of annual soil CO₂ emissions between MP and NT with different tillage treatments.However,rotation increased soil respiration rate in July and August by 3.4% and 5.9% compared with monoculture maize,respectively.（5）The effects of tillage methods and crop planting patterns on soil carbon release per unit yield vary from year to year,and the effects of this farming method and crop planting pattern on corn yield are reversed.There was no significant difference in soil carbon release from the average unit yield of autumn and no-tillage treatments under continuous cropping or rotation,and there was no significant difference in soil carbon release per unit yield between maize continuous cropping and corn-soil rotation.Effects of different tillages and planting patterns under extreme drought events induced by climate change:（1）There was no significant difference of soil respiration rate between MP and NT during the growing season.Although the soil respiration rate of MP in the early growing season was higher than that of NT,but lower than NT in the middle and late growth season（p < 0.05）.（2）There was no significant difference of annual soil CO₂ emissions between tillage treatments and planting.But the soil C emission per corn yield of MP was significantly higher than NT,which was 72% higher than CC and 78.8 higher than CR,respectively.（3）Soil temperature（5 cm,10 cm,20 cm）under MP was significantly higher by 8.0% and 7.0% than NT in June and July respectively（p < 0.05）.But soil temperature at 0–22 cm under MP was significantly lower by 38% than NT in July and August（average）.（4）Compared with MP,NT significantly increased soil microbial total,bacterial,and fungal PLFAs content from April to September.The largest increase occurred in April by 86.4%（total）,83.8%（bacteria）and 114.5%（fungi）,respectively.The lowest increase occurred in July when soil moisture content was less than 20%,but the ratio of F/B showed the greatest increase of 26.7% at this time.（5）Soil total,bacterial,fungal PLFA contents in a dry year were lower than that in normal year under MP except for June.The difference of soil total,bacterial and fungal PLFA contents between dry year and normal year under NT were higher than those under MP,even though the PLFA content in July was lower than the normal year both in MP and NT.From the perspective of soil carbon release,different tillages and planting patterns did not significantly affect the soil respiration rate and annual CO₂ emission but improving the soil water content（especially during extreme drought events）.It showed conservation tillage significantly enhanced maize yield,especially NT has significant yield advantages under extreme drought conditions.These results suggest that NT is a positive adaptation strategy to cope with drought under monoculture maize production in the black soil of northeast China,as well as farming measures that are conducive to soil organic carbon fixation in farmland.