Effects of Fenlong tillage and reducing nitrogen treatment on soil greenhouse gas emissions and soil enzyme activities in cassava field

【Objective】 The objective of the current study was to investigate influences on the greenhouse gas emission of soil and enzyme activities caused by Fenlong tillage(FLT)technology and nitrogen fertilizer application,to investigate the effect of planting cassava in FLT on yield increase and carbon emission reduction,and the existing cassava cultivation methods were optimized to provide technical support for sustainable development of cassava planting industry.【Method】 Cassava(Manihot esculenta Crantz)variety South China 205 was used as materials and cultivated using the FLT technology and the conventional tillage(CT)method,respectively. Four different nitrogen application rates were set up for both the FLT and CT. The conventional nitrogen application amount was set as 100%N treatment while other treatments were treated as 50%N,25%N and 0 N. Conventional phosphorus and potassium were used for all treatments. The fertilizer was applied as topdressing twice. Soil greenhouse gas emission and soil samples were collected from the first topdressing period to the cassava harvest season. The effects of combing tillage methods and nitrogen application on soil greenhouse gas emissions characteristics,the global warming potential(GWP),the greenhouse gas intensity(GHGI),soil carbon sequestration,soil urease and catalase activity were examined.【Result】 During the whole growth period of cassava,soil urease activity was higher under 100%N treatment and soil catalase activity was higher under 25%N treatment under the two tillage methods,and the enzyme activity under FLT was higher than that under CT. Soil greenhouse gas emissions,GWP,GHGI and soil carbon sequestration were all affected by tillage methods and nitrogen application rates. N₂O,CH₄ and CO₂ emissions,GWP,GHGI were decreased under nitrogen reduction treatment,and soil greenhouse gas emissions under 0 N treatment were the lowest. In the blocks using the conventional tillage method,GWP and GHGI of the 100%N treatment were 1170.4 kg/ha and 0.069 kg/kg,respectively,which were significantly higher than other nitrogen reduction treatments(P<0.05,the same below). For the blocks using FLT,the GWP and GHGI of the 100%N treatment were 367.6 kg/ha and 0.014 kg/kg,respectively. And there were no difference of GWP and GHGI between the 100%N and other nitrogen reduction treatments(P>0.05). With the same nitrogen application rate,the soil carbon sequestration of the FLT treatment was always significantly higher than which under the CT treatment. The highest carbon sequestration was found in the FLT treatment 100%N,and as high as 1.95 kg/(ha·a).【Conclusion】 FLT by optimizing the soil physical and chemical properties,improves the efficiency of soil nitrogen,improves soil carbon sequestration ability. Under the same experimental conditions,comparing with CT,FLT with 100%N treatment has the most obvious carbon emission reduction effect.