塔里木盆地南缘新垦农田土壤性状变化及其与小麦产量的关系

以塔里木盆地南缘不同年限新垦农田(10年、20年、30年、40年、50年)为研究对象,以未开垦的荒漠自然土壤为对照,测定0―40cm土层有机质、养分、盐碱等土壤性状,探讨了新垦农田土壤肥力和盐碱变化及其对小麦产量的影响。结果表明:随开垦年限延长,0―20,20―40cm土层有机质含量均呈线性增加,但后者变化幅度相对较小。在0―40cm土层,全氮、有效氮和速效钾含量随时间延长的变化均与有机质含量呈极显著正相关,开垦50年时分别增加88.8%,213.4%,37.5%;有效磷含量在开垦前30年呈线性增加而后又降低,开垦50年时比开垦前增加1201.2%。荒漠自然土壤(0年)是以Na+和Cl-为主的轻度盐渍化土壤,开垦为农田后总盐分含量显著下降,且不同年限间差异不明显,在0―40cm土层平均为0.8g/kg,离子累积转变为以Na+和HCO3-为主。土壤pH在开垦30年(pH为8.85)时比开垦前增加13.4%,之后又显著下降,pH变化与CO32-和K+累积呈显著正相关。新垦农田小麦产量平均为4.79 t/hm^2,与土壤有机质、养分、盐分含量和pH均不相关,但与Na+、Cl-含量均呈显著负相关。综上,随开垦时间延长绿洲农田土壤肥力和盐渍化程度已得到明显改善,但0―40cm土层Na+和Cl-含量却是影响新垦绿洲小麦产量的主要土壤因子。因此,培肥农田土壤,采取有效措施降低Na+和Cl-含量,并防止其再次升高是实现绿洲小麦稳产高产的关键。

Dynamic Changes of Soil Properties and Their Relationships with Wheat Yield in the New Reclaimed Farmland in the Southern Tarim Basin

In order to detect the dynamic changes of soil fertility and salt alkali and their effects on wheat yield, the newly reclaimed farmland (10, 20, 30, 40 and 50 years) in the south margin of Tarim Basin were taken as the research object, and the uncultivated desert natural soil was taken as the control, the soil properties, such as organic matter, nutrient and salt alkali of the surface soil (0-40 cm) were measured. The results showed that the organic matter content in the surface soil (0-20 cm and 20-40 cm) increased linearly with the extension of cultivation time, but the change range of organic matter content in 20-40 cm soil layer was relatively small. In the 0-40 cm soil layer, the changes of the total nitrogen, available nitrogen and available potassium content with time extension were all significantly positively correlated with organic matter content, which increased by 88.8%, 213.4 and 37.5% in 50 years of reclamation respectively compared with that of the native desert soil. Available phosphorus content increased linearly in the initial 30 years after cultivation and then decreased. However, it increased by 1 201.2% in 50 years after cultivation compared with the uncultivated soil. The nature desert soil was mildly salinized soil dominated by Na⁺ and Cl^-. The total salt content decreased sharply after cultivation, and the difference between different years was not obvious, and the average value of which was 0.8 g/kg in 0-40 cm soil layer. The dominate cation and anion of the cultivated oasis farmland changed to be Na⁺ and HCO₃^-. The pH value increased by 13.4% in the initial 30 years (pH 8.85) compared with the desert soil, and then decreased significantly. The change of pH was positively related with accumulation of CO₃^2- and K⁺. The average wheat yield in the new reclaimed farmland was 4.79 t/hm², and which was negatively related to the content of Na⁺ and Cl^-, but was not related to the content of soil organic matter, nutrients and total salt as well as pH value. In conclusion, continuous cultivation significantly improved soil fertility and salinization degree. However, the wheat yield was closely related with the content of Na⁺ and Cl^- in 0-40 cm soil layer. The results suggested that fertilizing oasis farmland soil and taking effective measures to reduce Na⁺ and Cl^- content from rising again were important to achieve stable and high yield of wheat in the study area.