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了解土壤磷素积累特征对调控磷肥使用、降低农田磷素的环境风险和保障生态环境安全具有重要意义。以黄土高原沟壑区的典型小流域为对象,分析了18年来(1986~2004年)综合治理条件下流域土壤全磷、有效磷(Olsen-P)含量的时空变化特征及其对土壤水溶性磷含量变化的影响。结果表明,截至到2004年,流域磷素积累由塬面逐步向塬坡和沟道扩展。2004年,农田土壤全磷(752 mg.kg-1)和Olsen-P(20.2 mg.kg-1)较1986年分别提高了45%和3.5倍,相当于每年全磷提高13 mg P.kg-1,Oslen-P每年提高1.0 mg.kg-1,流域50%的农田土壤Olsen-P含量超过15 mg.kg-1。与1993年大规模建立果园时相比,果园土壤全磷每年提高20~30 mg P.kg-1,Olsen-P每年提高3~4 mg.kg-1,2004年已有70%的果园土壤Olsen-P含量超过15 mg.kg-1,20~60cm土层的果园全磷和Olsen-p含量也逐渐提高。但林草地的全磷没有显著变化,Olsen-P依然低于5.0 mg.kg-1。1986年以来,无机磷肥的持续投入是流域土壤磷素积累的主导因素。流域土壤Olsen-P与全磷存在显著的线性相关关系(p<0.001);水溶性磷与Olsen-P含量呈显著的指数函数关系(p<0.001)。土壤磷素大量积累已成为黄土高原水土流失区当前十分迫切的农田环境问题。
It is of great significance to understand the characteristics of soil phosphorus accumulation to control the use of phosphate fertilizer, reduce the environmental risk of phosphorus in farmland and ensure the ecological security. Taking the typical small watershed in the gully area of the Loess Plateau as an example, the spatio-temporal variations of soil total phosphorus and available phosphorus (Olsen-P) under the comprehensive control conditions in the past 18 years (1986-2004) were analyzed and their effects on soil water-soluble phosphorus The impact of changes in content. The results show that as of 2004, phosphorus accumulation in the basin gradually expanded from plateau to plateau and channel. In 2004, total phosphorus (752 mg.kg-1) and Olsen-P (20.2 mg.kg-1) in farmland increased by 45% and 3.5 times respectively compared with that in 1986, equivalent to 13 mg Pkg -1 and Oslen-P increased by 1.0 mg.kg-1 every year. Olsen-P content in 50% of the farmland soil exceeded 15 mg.kg-1. Compared with the large-scale establishment of orchards in 1993, total phosphorus in orchards increased by 20-30 mg P. kg-1 per year and Olsen-P increased by 3-4 mg.kg-1 in 70% of the orchard soils in 2004 The contents of total phosphorus and Olsen-p in orchard with Olsen-P content over 15 mg.kg-1 and 20 ~ 60cm soil layer also increased gradually. However, there was no significant change in the total phosphorus in the grassland, and the Olsen-P was still below 5.0 mg.kg -1. Since 1986, the continuous input of inorganic phosphate fertilizer has been the dominant factor for phosphorus accumulation in the watershed. There was a significant linear correlation between soil Olsen-P and total phosphorus (p <0.001), and a significant exponential function (p <0.001) of water-soluble phosphorus and Olsen-P content. The massive accumulation of soil phosphorus has become a very urgent farmland environmental problem in the soil and water loss area of the Loess Plateau.