[Effect of Long-Term Biochar Application on Soil Respiration in Flue-Cured Tobacco Planting Fields in Henan Province]

A five year (2013-2017) experiment was conducted to explore the effects of biochar application on the dynamic changes in soil respiration, soil water, and heat factors under four treatments:CK (without biochar), T1 (with 1.5 t·hm^-2biochar), T2 (with 15 t·hm^-2biochar), and T3 (with 45 t·hm^-2biochar). The results showed that:① the soil respiration rate in the growing season of flue-cured tobacco was significantly reduced by 25.89% under the five year application of medium-dose biochar (T2:15 t·hm^-2) in soil, while it was significantly increased by 21.48% when the applied dose increased to 45 t·hm^-2(T3) (P<0.05). ② The long-term application of medium-dose biochar in the soil significantly reduced the soil heterotrophic respiration and autotrophic respiration rates by 29.80% and 28.75%, respectively. Meanwhile, the application of high-dose biochar (T3:45 t·hm^-2) significantly increased the heterotrophic respiration rate by 28.88%. In addition, the application of low-dose biochar (T1:1.5 t·hm^-2) and medium-dose biochar significantly increased the proportion of autotrophic respiration, whereas the high-dose biochar application significantly increased the proportion of heterotrophic respiration (P<0.05). ③ The addition of low-dose biochar to the soil significantly reduced the soil temperature at 5 cm in the growing season of flue-cured tobacco, while the high-dose application significantly reduced the soil humidity. There was a significant index correlation between soil respiration and soil temperature at 5 cm but no significant correlation with soil humidity at 5 cm (P<0.05). Ultimately, the application of low-dose biochar for five years in soil had no effect on soil respiration, and the application of the proper amount of biochar had a carbon sequestration effect. Additionally, large-dose biochar application may be counterproductive. It is recommended that the application range of biochar should be controlled within 15 t·hm^-2.