不同形态磷酸盐及施用方式对石灰性土壤磷移动性和有效性的影响

Mobility and availability of phosphate under different phosphate sources and application methods in calcareous soils

【目的】磷的固定是石灰性土壤中磷肥效益低的重要原因,研究两种施肥方式下不同形态磷源在石灰性土壤中的迁移以及有效性,为实现磷肥减施增效提供理论基础。【方法】采用土柱模拟试验方法进行研究,供试土壤为粘质和壤质石灰性土壤。供试磷酸盐为磷酸脲、焦磷酸和聚磷酸,壤土施磷量为0.0581 g/柱,粘土为0.0594 g/柱。施用方式包括一次施用和分4次滴施,同时以不施用磷酸盐土柱为对照。于地下室内(27±1.0)℃培养28天后将土柱在-80℃条件下快速冷冻固形,从土表向下0—100 mm内每隔5 mm作为一个切割单元,100—300 mm间每隔20 mm作为一个切割单元,测定每层土壤的水溶性磷和Olsen-P含量。【结果】培养28天后,一次施用条件下,磷在壤土中的移动距离表现为聚磷酸(90 mm)>焦磷酸(60 mm)>磷酸脲(50 mm),粘土中表现为聚磷酸(80 mm)>焦磷酸(70 mm)>磷酸脲(60 mm)。分次滴施条件下,聚磷酸(95 mm)在壤土中的移动距离比磷酸脲(65 mm)和焦磷酸(70 mm)分别增加46.2%和35.7%,在粘土中聚磷酸(90 mm)的移动距离较磷酸脲(70 mm)和焦磷酸(75 mm)分别增加28.6%和20.0%。磷浓度下降到一半时所达到土柱深度(半运移深度)的结果表明,在壤土一次施用条件下,半运移深度表现为聚磷酸(15.1 mm)>焦磷酸(11.4 mm)>磷酸脲(10.5 mm),分次滴施条件下半运移深度为聚磷酸(20.0 mm)>焦磷酸(14.4 mm)>磷酸脲(14.3 mm)。在粘土一次施用条件下,半运移深度为聚磷酸(17.7 mm)>焦磷酸(15.8 mm)>磷酸脲(14.8 mm),分次滴施条件下,聚磷酸、焦磷酸和磷酸脲的半运移深度依次为51.3、27.1和41.4 mm。相关性分析结果表明,不论一次施用还是分次滴施,聚磷酸和焦磷酸处理均随着水溶性磷含量的增加,有效磷含量在粘土上的增加量大于在壤土上的,分次滴施聚磷酸较一次施用在同样水溶性磷含量下,有效磷的含量在粘土和壤土中的差距减小,焦磷酸处理中水溶性磷与有效磷在两种土壤上较为接近。磷酸脲一次施用后,有效磷在粘土中随水溶性磷的变化量大于在壤土中,分次滴施结果则相反。【结论】在质地为壤土和粘土的石灰性土壤中,不论是一次性施用还是分次滴施,磷的移动性均表现为聚磷酸>焦磷酸>磷酸脲,且分次滴施3种磷源时磷的移动性和有效性均显著高于一次施用。同样水溶性磷含量条件下,粘土中磷的有效性高于壤土,分次滴施提高土壤磷素有效性的效果表现为粘土优于壤土。

【Objectives】The fixation of phosphorus(P)is a vital reason for low fertilizer effectiveness.Therefore,mobility of different phosphate sources under different application methods was compared in this paper,to provide reference for phosphorus fertilizer management.【Methods】A chamber simulation experiment was carried out at(27±1.0)℃,using calcareous clayey and loamy soils as tested materials.The amount of applied P was 0.0581 g/column in loamy soil and 0.0594 g/column in clayey soil.The tested P sources included polyphosphate,pyrophosphate and urea phosphate,which were all applied once on the surface and evenly divided into four parts and applied with watering in 7 days intervals(split application).Soil columns without adding P were used as the controls.After 28 days of treatment,the soil columns were immediately frozen and solidified at-80℃,then sliced in every 5 mm within the first 0-100 mm depth and in every 20 mm afterwards.The contents of water soluble P and Olsen-P in each layer of soil were determined.【Results】Under single application,the down movement of P from polyphosphate,pyrophosphate and urea phosphate were 90,60 and 50 mm in loamy soil,and 80,70 and 60 mm in clayey soil,respectively.Under split application,the down movement of P from polyphosphate in loamy soil(95 mm)was 46.2%and 35.7%higher than those from urea phosphate(65 mm)and pyrophosphate(70 mm),and that from polyphosphate in clayey soil(90 mm)was 28.6%and 20.0%higher than those from urea phosphate(70 mm)and pyrophosphate(75 mm),respectively.In loamy soil,the halfdepth of soil,which was the down distance with the water soluble P content half reduced,for polyphosphate,pyrophosphate and urea phosphate under single application were 15.1 mm,11.4 mm and 10.5 mm,under split application were 20.0 mm,14.4 mm and 14.3 mm;in clayey soil,the half-distance of polyphosphate,pyrophosphate and urea phosphate under single application were 17.7 mm,15.8 mm and 14.8 mm,and under split application were 51.3 mm,27.1 mm and 41.4 mm.Correlation analysis results showed that whether single or split application,the Olsen-P contents increased more in clayey soil than in loamy soil with the increase of water soluble P content.At the same water soluble P content,the discrepancy of Olsen-P contents between the loamy soil and clayey soil became narrow under split application of polyphosphate;the Olsen-P content in both soils was agreeable for pyrophosphate;the Olsen-P content increased more in clayey soil under single application of urea phosphate and opposite under split application.【Conclusions】In the calcareous loamy and clayey soil,the vertical downward movement distance of P is in order of polyphosphate>pyrophosphate>urea phosphate under both single and split application.And the mobility and availability of P in the soil columns are higher under split application than under single application.At the same water-P content,the availability of P in clayey soil is higher than that in loamy soil,and the effect of improving P availability in clayey soil is better than that in loamy soil under split application.