粉垄耕作与氮肥减施对木薯地土壤温室气体排放及土壤酶活性的影响

【目的】研究粉垄耕作与氮肥减施对木薯地土壤温室气体排放及土壤酶活性的影响，明确粉垄栽培木薯的增产及碳减排效应，为木薯种植业的可持续发展提供技术支撑。【方法】以木薯品种华南205为试验材料，利用粉垄耕作和常规耕作2种方式进行整地，分别设4个不同施氮量水平（100% N、50% N、25% N和0N），分2次追肥，于第1次追肥后至木薯收获期采集土壤温室气体及土壤样品，研究耕作方式及施氮量对土壤脲酶、过氧化氢酶活性及土壤温室气体排放量、净增温潜势（GWP）、温室气体强度（GHGI）和固碳量的影响。【结果】在木薯整个生育期中，2种耕作方式下，100% N处理的土壤脲酶活性较高，25% N处理的土壤过氧化氢酶活性较高，且粉垄耕作的酶活性整体上高于常规耕作。土壤温室气体累积排放量、GWP、GHGI和土壤固碳量均受耕作方式和施氮量的双重影响。减氮处理有利于降低土壤N₂O、CH₄和CO₂的累积排放量及GWP和GHGI，0N处理的土壤温室气体排放量均最低；常规耕作100% N处理的土壤GWP和GHGI分别为1170.4 kg/ha和0.069 kg/kg，均显著高于各减氮处理（P<0.05，下同）；粉垄耕作100% N处理的GWP和GHGI分别为367.6 kg/ha和0.014 kg/kg，与各减氮处理差异不显著（P>0.05）。相同施氮量处理下，粉垄耕作的土壤固碳量均显著高于常规耕作，其中100% N处理的土壤固碳量最高，为1.95 kg/（ha·a）。【结论】粉垄耕作可通过优化土壤理化性质，提高土壤固氮效率，改善土壤固碳能力。在相同的试验条件下，粉垄耕作100N%处理的碳减排效果最明显。

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.