The forms in which phosphorus (P) accumulates in soils are dependent on management practices, fertilizer sources, and methods of application, which may promote distinct P solubility and plant uptake. We aimed here to evaluate how soil tillage and phosphate fertilization strategies affected soil P fractions over 17 years and to identify best management practices for improving labile P fractions. The experiment was conducted in a very clayey Rhodic Ferralsol (Oxisol) with initially very low P availability, during 17 years under soybean and corn, fertilized with 35 kg P ha^–1 year^–1. Treatments were two soil management systems (CT-conventional tillage and NT-no-till) and four phosphate fertilization strategies (TSP – triple superphosphate or RRP – reactive rock phosphate, applied to the crop furrow or broadcast). Soil samples were taken at five depth layers, and organic (Po), inorganic (Pi), and total P (Pt) were determined by Hedley’s sequential fractionation. CT resulted in a more homogeneous distribution of Pi fractions throughout the soil profile, while under NT there was a steep depth gradient characterized by Pi accumulation in the fertilizer application zone. NT resulted in accumulation of Pi in more labile fractions and higher accumulation of Po physically protected by aggregation, both compared to CT. Also, under NT with RRP, there was a great accumulation of Pi associated with calcium (HCl Pi) compared to TSP, especially when the fertilizer was broadcast applied. An accumulation of Po down to 20 cm (CT) and 10 cm (NT) was also detected, compared to Cerrado natural soil. NT and RRP positively affected legacy P fractions and can be recommended as strategies to improve P fertilizer use efficiency.

磷（P）在土壤中累积的形式取决于管理措施，肥料来源和施用方法，这可能会促进磷的独特溶解度和植物吸收。我们的目标是评估土壤耕作和磷酸盐施肥策略如何影响17年间的土壤P组分，并确定改善不稳定P组分的最佳管理方法。该实验是在非常黏稠的Rhodic Ferralsol（Oxisol）中进行的，最初的P利用率非常低，在大豆和玉米中17年，施肥35 kg P ha – ¹年^–1。处理方法有两种：土壤管理系统（常规耕作和NT免耕）和四种磷酸盐施肥策略（TSP –三重过磷酸钙或RRP –活性磷肥，应用于作物犁沟或播种）。在五个深度层上采集土壤样品，并通过Hedley的连续分级法确定有机（Po），无机（Pi）和总P（Pt）。CT导致整个土壤剖面中Pi组分的分布更加均匀，而在NT下，陡峭的深度梯度以Pi在施肥区的积累为特征。与CT相比，NT导致Pi在更不稳定的级分中积累，而物理上受聚集保护的Po积累率更高。此外，在NT和RRP的作用下，与TSP相比，与钙相关的Pi积累量很大（HCl Pi），特别是在肥料播种时。与塞拉多天然土壤相比，还发现了低至20 cm（CT）和10 cm（NT）的Po积累。NT和RRP对遗留的P组分产生积极影响，可以建议将其作为提高P肥料使用效率的策略。