CO₂-C evolution rate in an incubation study with straw input to soil managed by different tillage systems

A laboratory incubation experiment was conducted to assess the impact of straw input on CO₂-C emissions. After the winter wheat (Triticum aestivum L.) growing season, soil samples were collected from the 0-20 cm soil layer. The experiment was conducted on a brown loam soil, classified as a Udoll according to the U. S. soil taxonomy. Treatment levels consisted of three tillage practices: sub-soiling (ST), no-till (NT) and the conventional tillage (CT), two straw management (with and without input of straw), three temperature (25, 30 and 35 °C), and three moisture regimes (55%, 65% and 75% of field moisture capacity or FMC). The results showed that the rate of straw decomposition was the highest in the soil under NT management. The relationship between rate of cumulative CO₂-C and straw decomposition was significant under NT (R ² = 0.52). The soil CO₂-C release under incubation was significantly higher with than without the input of straw (R ² = 0.95). Furthermore, soil respiration increased with increases in incubation temperature and FMC. At 75% FMC, the rate of CO₂-C release increased by 21.9 mg kg^-1 d^-1 at 30 °C and 32.0 mg kg^-1 d^-1 at 35 °C compared with that at 25 °C. At 35 °C, the rate of CO₂-C release increased by 43.6 mg kg^-1 d^-1 at 65% FMC and 51.2 mg kg^-1 d^-1 at 75% FMC incubation than that of at 55% FMC under ST. The degree of control on the CO₂-C evolution rate during the pre-incubation period and with higher incubation temperature and FMC was better for the soil from NT than that from CT and ST, and better yet for the soil from ST than that from CT.