Effects Of Warming And Straw Application On Soil Respiration And Enzyme Activities In A Cropland

In order to investigate the effects of warming and straw application on soil respiration and enzyme activities, randomized block experiments were performed in a winter wheat-soybean rotation cropland. There were four treatments, which were control (CK), warming (W), straw (S), warming and straw (WS). There were three replicates for each treatment. A portable soil CO2 fluxes system (LI-8100) was used to measure soil repatriation rates for all treatments. Soil temperature and moisture were simultaneously measured when soil respiration rates were measured. Soil urease, invertase, and catalase activities were measured during different crop development stages.Results showed that soil respiration rates for different treatments had the similar seasonal variability patterns, which was in accordance with the variability in soil temperature in two rotation seasons. During the 2014?2015 winter wheat-soybean growth season,soil respiration rates for CK, W,S and WS treatments were 1.71 ±0.03,2.47±0.04, 2.20±0.05,2.95±0.01 ?mol·(m2·s)-1,respectively. ANOVA showed that there were significant (p < 0.05) differences in soil respiration rates between CK and W, between CK and S, and between CK and WS treatments. Soil respiration rate in the W, S and WS treatment was significantly (p < 0.05) higher than that in the CK treatment.During the 2015?2016 winter wheat-soybean growth season,soil respiration rates for CK,W,S and WS treatments were 2.03±0.06?2.76±0.04?2.88±0.03?3.24±0.03 ?mol·(m2·s)-1, respectively. ANOVA showed that there were significant (p< 0.05) differences in soil respiration rates between CK and W, between CK and S,and between CK and WS treatments. The variation patterns of soil respiration in the 2015?2016 growth season were similar with that in the 2014?2015 growth season.Warming, straw application and warming and straw application enhanced soil respiration. At the same time, soil temperature is an important factor. In both of the two rotation years, the seasonal variability in soil respiration rate was affected by soil temperature. The exponential regression functions can be used to explain the relationship between soil respiration and soil temperature.During the 2014?2015 winter wheat growth season, warming and straw application enhanced the invertase activity at the elongation stage, there were no significant (p > 0.05) differences in catalase activities between CK and other treatments.At the booting stage, there was significant (p < 0.05) difference in urease and invertase activity between CK and other treatments. During the 2015 soybean growth season, warming enhanced the invertase activity at the seeding stage. At the flowering stage, there was significant (p < 0.05) difference in invertase activity between CK and other treatments. At the seed filling stage, warming enhanced urease activity, straw application enhanced invertase activity, there were no significant (p >0.05) differences in catalase activities between CK and other treatments. During the 2015?2016 winter wheat growth season, warming and straw application enhanced the invertase activity at the elongation, booting and anthesis stage. At the booting and anthesis stage, warming and straw application enhanced the catalase activity.Warming and straw application enhanced urease activity at the anthesis stage. During the 2016 soybean growth season, warming and straw application enhanced the invertase activity at the seeding and flowering stage. At the seed filling stage, every treatment enhanced urease, invertase and catalase activity. Warming and straw application enhanced urease, invertase and catalase activity.The relationship between soil respiration and urease, invertase and catalase activity can be described by a linear regression equation. In the 2014-2015 winter wheat growth season, the relationship between soil respiration and urease activity can be fitted by a linear regression function ( P =0.061) . The relationship between soil respiration and invertase activity can be explained by a significant (P = 0.013)linear function. The relationship between soil respiration and catalase activity can be explained by a very significant (P = 0.002) linear function. In the 2015 soybean growth season, the relationship between soil respiration and urease activity can be explained by a significant (P = 0.028) linear function. The relationship between soil respiration and invertase activity and catalase activity can be fitted by a linear regression function, with the P value of 0.111 and 0.215. In the 2015?2016 winter wheat growth season, the relationship between soil respiration and urease activity can be explained by a significant (P = 0.016) linear function. The relationship between soil respiration and invertase activity can be explained by a significant (P ?0.015) linear function. The relationship between soil respiration and catalase activity can be explained by a significant (P = 0.038) linear function. In the 2016 soybean growth season, the relationship between soil respiration and urease activity can be explained by a significant (P = 0.045) linear function. The relationship between soil respiration and invertase activity can be fitted by a linear regression function(P?0.072). The relationship between soil respiration and catalase activity can be explained by a very significant (P = 0.008) linear function. Urease, invertase and catalase are three important factors to affect soil respiration.