施氮对干热河谷农田土壤有机碳及其组分的影响

Effects of nitrogen application on agricultural soil organic carbon and its components in the dry-hot valley

干热河谷农业土壤环境长期承受“大水大肥”生产方式的胁迫,开展高温、干旱农田环境中氮肥施用与土壤有机碳固持间关系研究是维持土壤肥力、提高作物产量、实现农业可持续发展的重要科学基础。以干热河谷优势作物番茄为研究对象,设置4个施氮量处理(0、125、225、325 kg/hm^(2))开展田间施肥试验,探讨不同施氮量对番茄农田0~50 cm不同土层总有机碳(SOC)、活性有机碳(AOC)、非活性有机碳(NOC)、微生物量有机碳(MBC)和可溶性有机碳(DOC)的量变特征及其相互作用关系。结果表明:(1)与对照相比,低氮施肥处理10~50 cm土层的SOC含量显著增加(P<0.05),中氮施肥处理耕作层0~30 cm的SOC含量显著增加(P<0.05),高氮施肥处理在各个土层SOC含量均有小幅增加;(2)高氮施肥处理0~30 cm土层的AOC含量显著增加(P<0.05),0~50 cm土层的MBC含量及其分配比例也显著增加(P<0.05);中氮施肥处理0~30 cm土层的DOC含量显著增加(P<0.05);低氮施肥处理10~50 cm土层NOC含量及其分配比例显著增加(P<0.05);(3)不同氮肥处理的SOC含量及活性有机碳组分含量呈现逐层减少的趋势;(4)中高氮施肥处理下土壤AOC与SOC含量呈显著正相关关系(P<0.05),无氮处理的NOC与SOC含量呈极显著正相关关系(P<0.01),MBC和DOC含量也在一定程度上显著影响SOC含量(P<0.05);(5)番茄产量随施氮量的增加而增加,耕层0~30 cm的MBC含量与番茄产量显著正相关(P<0.05)。因此,在干热河谷冬春季番茄生产中,建议适量减少氮肥施用量至225 kg/hm^(2),不仅有利于作物对有机碳的吸收利用,增加土壤有机碳储量,而且能提高番茄产量,减少农业投入成本和环境污染风险。

The agricultural soil environment of dry-hot valley has long been under the stress of“large water and large fertilizer”intensive practices.The study on the relationship between nitrogen fertilizer application and soil organic carbon sequestration in high-temperature and arid farmland environment provides an important basis for maintaining soil fertility,improving crop yields,and developing sustainable agriculture.Tomato,the dominant crop in the dry-hot valley,was selected as the research object.A field fertilization experiment under different nitrogen application rates of 0,125,225,325 kg/hm^(2),was conducted to quantify the variation and their interaction of total organic carbon(SOC),active organic carbon(AOC),non-active organic carbon(NOC),microbial biomass organic carbon(MBC)and dissolved organic carbon(DOC)at 0~50 cm soil layers in tomato farmland of high-temperature and arid area.The results showed that:(1)Compared to the control group,the SOC concentration in 10~50 cm soil layer was significantly increased under low N treatment(P<0.05),and the SOC concentration in 0~30 cm soil layer was significantly increased under medium N treatment(P<0.05),and the SOC concentration increased slightly at each soil layer under high nitrogen treatment.(2)The application of high nitrogen fertilizer significantly increased AOC concentration in 0~30 cm soil layer,and MBC concentration and its distribution ratio in 0~50 cm soil layer(P<0.05).The application of medium nitrogen fertilizer significantly increased DOC concentration in 0~30 cm soil layer(P<0.05).The application of low nitrogen fertilizer significantly increased NOC concentration and its distribution ratio in 10~50 cm soil layer(P<0.05).(3)The concentration of SOC and active organic carbon components under different nitrogen fertilizer application treatments decreased gradually with soil layer increasing.(4)There was a significantly positive correlation between AOC and SOC content under medium and high nitrogen treatments(P<0.05),and an extremely significantly positive correlation between NOC and SOC content under no nitrogen treatment(P<0.01);MBC and DOC also significantly affected SOC content(P<0.05).(5)The tomato yield generally increased with nitrogen application increasing,and there was a significantly positive correlation between MBC content and tomato yield in the surface layer of 0~30 cm.Therefore,in winter and spring tomato production in the dry-hot valley it is recommended to reduce the application of nitrogen fertilizer at 225 kg/hm^(2),because the application of medium nitrogen fertilizer not only enhanced the absorption and utilization of organic carbon by crops roots and increased the soil organic carbon storage,but also increased the yield of tomato,reduced agricultural input costs and environmental pollution risk.