紫云英与稻草还田替代部分化肥对双季稻产量和土壤活性有机碳的影响

Effects of Returning Chinese Milk Vetch and Rice Straw to Replace Partial Fertilizers on Double Season Rice Yield and Soil Labile Organic Carbon

【目的】基于连续4年田间定位试验,探究紫云英与稻草翻压还田替代部分化肥对双季稻产量以及稻田土壤有机碳组分、碳库管理指数的影响。【方法】开展双季稻田间定位试验,测定早、晚稻产量及连续试验4年后的土壤有机碳和土壤高活性、中活性、活性及非活性有机碳含量,计算土壤碳库管理指数。试验设6个处理:(1)冬闲+氮、磷、钾化肥(CF);(2)翻压紫云英+氮、磷、钾化肥(MV);(3)冬闲+稻草低量还田+氮、磷、钾化肥(RSl);(4)冬闲+稻草高量还田+氮、磷、钾化肥(RSh);(5)翻压紫云英+稻草低量还田+氮、磷、钾化肥(MV+RSl);(6)翻压紫云英+稻草高量还田+氮、磷、钾化肥MV+RSh)。晚稻收获后,采集0—15 cm耕层土壤,采用重铬酸钾法测定土壤有机碳含量,高锰酸钾氧化法测定土壤高活性(33 mmol·L^(-1))、中活性(167 mmol·L^(-1))、活性(333 mmol·L^(-1))有机碳含量。【结果】等氮磷钾养分投入量下,MV+RSh处理的双季稻产量与CF、RSl处理差异显著,其他处理间水稻产量无显著差异,双季稻总产量RSl处理最高,为13347 kg·hm-2,MV+RSh处理最低,为11687 kg·hm^(-2)。连续试验4年后,MV+RSh、RSh、MV+RSl、RSl、MV处理的土壤有机碳含量分别显著增加42.0%、32.9%、29.9%、28.3%、26.3%(P<0.05);各处理的土壤活性有机碳含量提高了23.9%—56.4%,MV+RSh、RSh、MV+RSl、RSl、MV处理土壤非活性有机碳含量分别显著增加了37.3%、28.6%、25.8%、24.1%、23.4%(P<0.05)。相比CF处理,MV+RSh、MV+RSl、MV、RSh、RSl处理下土壤高活性有机碳含量增加了12.3%—27.7%,中活性有机碳含量增加了5.6%—20.0%,活性有机碳含量增加了9.9%—26.3%。翻压紫云英和稻草还田显著提高了土壤碳库管理指数,CF、MV、RSl、MV+RSl、RSh、MV+RSh处理使得土壤碳库管理指数增加了25.5%—61.7%。【结论】连续4年等氮磷钾养分投入下,翻压紫云英、稻草还田替代部分化肥用量可以保证双季稻产量,提高土壤有机碳含量,且有利于增加土壤高活性、中活性、活性及非活性有机碳的含量,皆以MV+RSh处理增加最显著,与仅紫云英还田相比,仅稻草还田对增加土壤有机碳含量贡献更大。综上,在南方双季稻区,在一定替代范围内,紫云英和稻草还田可以减少化肥用量,保证水稻产量。

【Objective】The purpose of this study was to investigate the effects of replacing partial chemical fertilizers with Chinese milk vetch and rice straw on double rice yield and the soil labile organic carbon fractions,carbon pool management index of the paddy soil based on four consecutive years of field experiment.【Method】The double-season rice field experiment was conducted,and then yield of rice yield early and late rice,contents of soil organic carbon,soil high labile,medium labile,labile and no labile organic carbon were measured after four years experiment,then soil carbon pool management index were calculated.There were six treatments:(1)Winter fallow+N,P,K(CF);(2)Chinese milk vetch+N,P,K(MV);(3)Winter fallow+low weight of rice straw returning+N,P,K(RSl);(4)Winter fallow+high weight of rice straw returning+N,P,K(RSh);(5)Chinese milk vetch+low weight of rice straw returning+N,P,K(MV+RSl);(6)Chinese milk vetch+high weight of rice straw returning+N,P,K(MV+RSh).After harvest of late rice,0-15 cm surface soil was collected.Potassium dichromate method was used to determine the content of soil organic carbon,and potassium permanganate oxidation method was used to determine the content of soil organic carbon with high labile(33 mmol·L_(-1)),medium labile(167 mmol·L^(-1))and labile(333 mmol·L^(-1)).【Result】Under the equal nitrogen,phosphorus and potassium nutrient inputs,the double-season rice yield under the MV+RSh treatment differed significantly from the CF and RSl treatments,while there was no significant difference in rice yield between the other treatments,and the total double-season rice yield was the highest under the RSl treatment at 13347 kg·hm^(-2) and the lowest in the MV+RSh treatment at 11687 kg·hm-2.After four years of continuous trials,the MV+RSh,RSh,MV+RSl,RSl,and MV treatments significantly increased soil organic carbon by 42.0%,32.9%,29.9%,28.3%,and 26.3%(P<0.05),respectively;soil labile organic carbon content was increased by 23.9%-56.4%in each treatment,and soil no labile organic carbon content under MV+RSh,RSh,MV+RSl,RSl,and MV treatments significantly was increased by 37.3%,28.6%,25.8%,24.1%and 23.4%(P<0.05).Compared with the CF treatment,soil high labile organic carbon was increased by 12.3%-27.7%,medium labile organic carbon was increased by 5.6%-20.0%,and labile organic carbon was increased by 9.9%-26.3%under MV+RSh,MV+RSl,MV,RSh and RSl treatments.The CF、MV、RSl、MV+RSl、RSh、MV+RSh treatments increased the soil organic carbon pool management index by 25.5%-61.7%.【Conclusion】Under four consecutive years of equal nitrogen,phosphorus and potassium nutrient inputs,returning Chinese milk vetch and rice straw replacing part of the chemical fertilizer dosage could ensure double-season rice yields and increase soil organic carbon content,and also help to increase the content of high labile,medium labile,labile and no labile soil organic carbon,all of which were most significantly increased by the treatment of MV+RSh.The contribution of rice straw alone to the increase in soil organic carbon content was greater than that of Chinese milk vetch alone.To sum up,in the southern double-season rice area,within a certain range of substitution,the return of Chinese milk vetch and rice straw to the field could reduce the amount of chemical fertilizer and ensure rice yield,which was of great significance for green and sustainable rice production.