Responses of Soil Respiration and Organic Carbon to Straw Mulching and Ridge Tillage in Maize Field of a Triple Cropping System in the Hilly Region of Southwest China

Soil disturbance by tillage practices promotes soil respiration which is a main source of carbon dioxide emission into the atmosphere. The present study was conducted to investigate the effect of different tillage practices on soil respiration and the carbon source/sink characteristics of maize farmland ecosystems in the wheat-maize-soybean cropping system. Six tillage treatments, namely, traditional tillage (T), ridge tillage (R), traditional tillage + straw mulching (TS), ridge tillage + straw mulching (RS), traditional tillage + straw mulching + decomposing inoculants (TSD), and ridge tillage + straw mulching + decomposing inoculants (RSD), were used to measure the soil respiration and its hydrothermal factors. The results showed that the intensity of soil respiration increased initially and decreased afterwards throughout the growth period of maize ranging from 1.011 to 5.575 mol (m(2)s)(-1). The soil respiration rate under different treatments varied remarkably presenting a trend of RSD > TSD > TS > RS > T > R. Ridge tillage reduced the soil respiration rate of maize farmland while straw mulching improved it. Meanwhile, ridge tillage and straw mulching increased the soil temperature sensitivity index of soil respiration, but the addition of decomposing inoculants reduced this trend. The soil moisture response threshold under ridge tillage was lower, while the straw mulching was found to increase it, compared with the control. Moreover, there was a positive correlation between trapped soil fauna and soil respiration. Compared with the control, ridge tillage and straw mulching were beneficial to the carbon sink of the farmland ecosystem as shown by the maize field for the entire growing season.