黄土塬区不同土地利用方式对土壤理化性质的影响

Effects of Different Land Use Patterns on Soil Physicochemical Properties in the Loess Plateau Area

[目的]为探讨不同土地利用方式对黄土塬区土壤理化性质的影响。[方法]以裸地为对照(CK),设置常规施肥农田(H)、不施肥农田(L)、苜蓿草地(A)4个不同的利用方式于2005年开始在陕西长武开展长期定位试验,并于2021年7月对4个样地0-200 cm土壤的理化性质进行分析测定。[结果]经过17年长期定位试验后,农田和草地对土壤理化性质的影响差异明显。(1)在土壤表层0-40 cm,苜蓿草地黏粒和粉粒颗粒体积分数较其他3个样地略有提高,沙粒体积分数略有降低趋势,而裸地处理黏粒和细粉粒比例有降低趋势。(2)与裸地相比,苜蓿草地0-20 cm土层土壤pH显著增加0.8%,施肥农田显著降低1.7%;除80-100 cm土层外,施肥农田土壤pH在0-200 cm剖面内整体显著低于其他3个处理。与裸地相比,在0-20 cm土层,苜蓿草地和施肥农田的有机碳储量、有机质和氮素显著增加,且苜蓿草地高于施肥农田;苜蓿草地与不施肥农田的有效磷和速效钾显著降低,施肥农田的速效钾也显著降低;不施肥农田碱解氮和硝铵态氮显著降低。(3)在不同土地利用方式下,土壤有机质、有机碳及全氮随着土层深度的加深表现出先降低,至60 cm后升高,到100 cm再次降低的趋势;草地的土壤有效磷在60 cm土层以下逐渐增加;其余养分指标在0-200 cm空间垂直分布整体呈下降趋势。(4)0-100 cm土壤有机质、全氮、碱解氮、硝铵态氮呈显著正相关,有效磷与有机质、全氮、碱解氮、pH呈显著负相关;100-200 cm有机质与速效钾呈显著正相关,有效磷与pH呈显著负相关。[结论]黄土塬区合理的农田管理和连续种植苜蓿均可使有机质、全氮和速效氮等养分指标维持在较高水平,在一定程度上保障土壤质量。为促进该区域土壤的可持续性,建议农田中适当增加钾肥和有机肥的投入,而草地则需要补充适量的磷钾肥。

[Objective]In order to explore the effects of different land use patterns on soil physicochemical properties in the Loess Plateau area.[Methods]This study used bare land as a control(CK),and set four different use patterns as conventional fertilization farmland(H),unfertilization farmland(L),and alfalfa grassland(A)in Changwu,Shaanxi Province since 2005.The physical and chemical properties of 0-200 cm soil in the four plots were determined in July 2021.[Results]After 17 years,there were significant differences between farmland and grassland on soil physicochemical properties.(1)In 0-40 cm soil surface,the volume fraction of clay and powder in alfalfa field slightly increased compared with the other three plots,the volume fraction of sand slightly decreased,while the proportion of clay and fine powder in bare field decreased.(2)In the 0-20 cm of the soil,compared to bare land,soil pH significantly increased by 0.8%in alfalfa grassland,and significantly decreased by 1.7%in fertilized farmland.Except for 80-100 cm,soil pH in 0-200 cm section of fertilized farmland was significantly lower than that in the other three plots.Compared with bare land,in the 0-20 cm of the soil,the organic carbon storage,organic matter and nitrogen content of alfalfa grassland and fertilized farmland increased significantly and the contents of them from alfalfa grassland was higher than those of fertilized farmland.The content of available phosphorus and available potassium of alfalfa grassland and unfertilized farmland decreased significantly.The content of available potassium of fertilized farmland also decreased significantly.The content of alkaline dissolved nitrogen and nitrate-ammonium nitrogen of unfertilized farmland decreased significantly.(3)Under different land use patterns,soil organic matter,organic carbon and total nitrogen showed a decreasing trend from 0 to 60 cm,then an increasing trend showed until it reached 100 cm depth and after where a decreasing trend showed again with the deepening of the soil layer.The available phosphorus content of the soil in grassland gradually increased after 60 cm.The vertical distribution of other nutrient indexes in 0-200 cm space showed a downward trend.(4)There was a significant positive correlation between soil organic matter,total nitrogen,alkaline dissolved nitrogen and nitrate-ammonium nitrogen at 0-100 cm,and a significant negative correlation between available phosphorus and organic matter,total nitrogen,alkaline dissolved nitrogen and pH.There was a significant positive correlation between soil organic matter and available potassium at 100-200 cm,and a significant negative correlation between available phosphorus and pH.[Conclusion]Reasonable farmland management and continuous planting of alfalfa in the Loess Plateau area can keep the nutrient indexes of organic matter,total nitrogen and available nitrogen at a high level,which can guarantee soil quality to a certain extent.In order to promote the sustainability of soil in this region,it is recommended to increase the input of potassium fertilizer and organic fertilizer in farmland,while the grassland needs to supplement the appropriate amount of phosphate and potassium fertilizer.