Andisols, rich in minerals like allophane, imogolite and iron- (Fe) or aluminum- (Al) oxides have high phosphorus (P) sorption capacity and require annual P additions to ensure plant productivity. It is known that the use of composted poultry manure (PM) increases soil labile P and carbon concentration, although the mechanisms controlling P availability and soil organic carbon (SOC) sequestration are not fully understood. The aim of this study was to investigate the relationship between soil available P and particles size distribution, SOC, and iron and aluminum complexes on Southern Chilean pastures with long-term PM amendment. Soil samples, were collected from 4 pastoral farms where PM had been applied annually at 3 tons ha⁻¹ for 5 and 10 years. We analyzed for elemental concentrations, P forms through a modified P fractionation methodology and aggregation through particle size analyses and scanning electron microscopy. Moreover, we determined oxalate and pyrophosphate extractable Fe and Al.

Andisols receiving long-term PM amendment had 22–65% higher SOC contents than unfertilized control likely due to improved aggregation capacity as indicated by greater soil particle size. Moreover, the readily available inorganic P increased by 56 to 286% between control and PM amended soils. Andisols amended with PM also showed lower oxalate extractable Al and Fe and higher pyrophosphate extractable forms. These parameters correlated with SOC, labile P concentrations and particle size distribution. We concluded that increased P availability under pastures growing on Andisol with long-term PM amendment is regulated by three mechanisms related to input of readily available P, release of native soil P and decreased availability of sorption sites.

富含象石烷，伊毛go石和铁（Fe）或铝（Al）氧化物等矿物的山iso醇具有高的磷（P）吸附能力，并且每年需要添加磷以确保工厂的生产力。众所周知，使用堆肥家禽粪肥（PM）会增加土壤中不稳定的P和碳浓度，尽管控制P的有效性和固存有机碳（SOC）的机制尚未得到充分理解。这项研究的目的是研究长期施用PM改良剂的智利南部牧场土壤速效磷与粒径分布，SOC和铁铝复合物之间的关系。从4个牧场农场收集土壤样品，这些农场每年施用PM为3吨公顷^-15年和10年。我们分析了元素浓度​​，通过改进的P分馏方法得到的P形式以及通过粒度分析和扫描电子显微镜进行的聚集。此外，我们确定了草酸盐和焦磷酸盐可萃取的铁和铝。

接受长期PM修正的山iso醇的SOC含量比未施肥的对照高22–65％，这可能是由于土壤颗粒尺寸增大表明聚集能力提高所致。此外，在对照和PM改良土壤之间，易于获得的无机P增加了56％至286％。用PM改性的山iso醇也显示出较低的草酸盐可萃取Al和Fe以及较高的焦磷酸盐可萃取形式。这些参数与SOC，不稳定的P浓度和粒度分布相关。我们得出的结论是，在经过长期PM修正的Andisol上生长的牧场下，磷的有效性增加受到三种机制的调节，这些机制与速溶磷的输入，天然土壤磷的释放和吸附位点的可用性降低有关。