农艺措施对干旱区棉田土壤有机碳及微生物量碳含量的影响

【目的】探讨干旱区绿洲棉田农艺措施对土壤有机碳（SOC）及微生物量碳含量（MBC）的影响，揭示农艺措施对农田生态系统土壤碳稳定性的影响机制，为干旱区农业资源高效利用及可持续发展提供理论依据。【方法】试验采用裂裂区设计，以膜下滴灌和常规漫灌2种灌溉方式为主区，秸秆还田与秸秆不还田2种处理为裂区，4种施肥处理：单施有机肥（为腐熟鸡粪，OM）、单施氮磷钾化肥（NPK）、氮磷钾化肥与有机肥配施（NPK+OM）和不施肥（CK）为裂裂区。于棉花出苗后开始测定土壤异氧呼吸强度，并于每年棉花收获期采集土壤样品，测定和分析不同农艺措施下绿洲棉田土壤有机碳及微生物量碳含量。【结果】干旱区绿洲棉田不同农艺措施两两交互及3种措施交互作用下土壤有机碳、微生物量碳含量差异均不显著（P＞0.05）。土壤有机碳、微生物量碳含量表层0—20 cm含量均最高，其下层随着土壤深度的增加呈逐渐降低的趋势，至40—60 cm土层降至最低。不同农艺措施下，土壤有机碳含量变化表现为，与常规漫灌方式相比，膜下滴灌方式增加了2.5%—3.0%，秸秆还田比秸秆不还田增加了2.3%—6.3%，与CK处理相比，（NPK+OM）处理土壤有机碳含量增加了14.3%—16.8%，且（NPK+OM）/OM处理土壤有机碳含量显著大于CK/NPK处理（P＜0.05）。土壤微生物量碳含量为膜下滴灌方式比常规漫灌方式增加了21.9%—34.3%，秸秆还田比秸秆不还田增加了12.1%—29.4%，与CK处理相比，（NPK+OM）处理土壤微生物量碳含量增加了83.9%—151.0%。棉田土壤微生物熵（qMB）的大小变化在灌溉处理间表现为膜下滴灌>常规漫灌方式，秸秆处理间为秸秆还田>秸秆不还田处理，施肥处理间土壤微生物熵在0—40 cm土层显著大于40—60 cm土层，且不同土层间（NPK+OM）处理土壤微生物熵为最大，其次分别为OM、NPK、CK处理。棉田土壤微生物代谢熵（qCO₂）大小变化在不同灌溉处理间表现为膜下滴灌低于常规漫灌方式，秸秆处理间为秸秆还田低于秸秆不还田处理，施肥处理间为（NPK+OM）

Effects of Agronomic Measures on Soil Organic Carbon and Microbial Carbon Content in Cotton in Arid Region

【Objective】To reveal the regulatory mechanism of agronomic measures on soil carbon stability of the agro-ecosystem in arid region, an experiment was carried out to study the effects of agricultural practices on soil organic carbon (SOC) and microbial biomass carbon (MBC) of cotton fields, which would a provide theoretical basis for agricultural resources utilization and sustainable development in the oasis arid region.【Method】In this study, the split-split plot design method was used to arrange the treatments during cotton growth period. In the main plot treatment, two irrigation methods were designed: drip irrigation and flood irrigation. The split-plot treatment consisted of two stubble management measures: stubble-incorporated and stubble-removed. The split-split-plot treatment was composed of four fertilizer treatments: organic manure (chicken manure, which was composted before utilization, OM), N P K fertilizer (NPK), combined application of NPK fertilizer and organic manure (NPK+OM), and no fertilization (CK). The soil heterotrophic respiration intensity was measured after emergence of the cotton seedling, and soil samples were collected in the annual cotton harvest period. The soil organic carbon and microbial biomass carbon of cotton fields were measured under different agronomic measures.【Result】Both soil organic carbon and microbial biomass carbon were not significant under the condition of interaction between different agronomic measures (P＞0.05). The soil organic carbon and microbial biomass carbon at 0-20 cm surface soil were the highest, with lower distribution trends as soil layer depth increased of cotton field, and reduced to lowest at 40-60 cm soil layer in the oasis arid region. The soil organic carbon under conventional flood irrigation was 2.5%-3.0% more than that under drip irrigation under mulch, and under stubble incorporation was 2.3%-6.3% more than that under stubble removal, and as compared with CK treatment, the soil organic carbon under NPK+OM fertilization increased by 14.3%-16.8%, and the soil organic carbon of (NPK + OM) and OM treatment were significantly greater than CK and NPK treatment (P＜0.05). The microbial biomass carbon under drip irrigation under mulching was 21.9%-34.3% more than that under conventional flood irrigation method, and under stubble incorporation was 12.1%-29.4% more than that under stubble removal, and as compared with CK treatment, the microbial biomass carbon under NPK+OM fertilization increased by 83.9%-151.0%. The soil microbial quotient (qMB) was larger under drip irrigation under mulching than those under conventional flood irrigation among the irrigation treatments, and the soil microbial quotient was larger with stubble incorporation relative to removal among the stubble treatments, and the soil microbial quotient at 0-40 cm soil layer was larger than that 40-60 cm soil layer among the fertilization treatments, and the soil microbial quotient was the highest under NPK+OM fertilization, and OM, CK, and NPK, respectively. The soil microbial metabolic quotient (qCO₂) was smaller under drip irrigation under mulching than under conventional flood irrigation among the irrigation treatments, and the soil microbial metabolic quotient was smaller with stubble incorporation relative to removal among the stubble treatments, and lowest under NPK+OM fertilization (followed by OM, NPK, and CK) among the fertilization treatments, and the soil microbial metabolic quotient of (NPK + OM) treatment was significantly compared with other fertilization treatments (P＜0.05). Under the conditions of interaction between different agronomic measures, the soil microbial metabolic quotient was the lowest in the NPK+OM treatment with stubble incorporation under drip irrigation under mulching.【Conclusion】In arid region, cotton production using reasonable agronomic measures, such as water saving technology of drip irrigation under mulching, combined with application of NPK fertilizer and organic manure and straw incorporation, could not only further improve soil quality, but are also be conducive to the sustainable utilization of agricultural soils.