Continuous crop expansion has led to a growing demand for phosphate fertilizers. A sound knowledge of the dynamics of phosphorus, and its interaction with iron oxides and organic matter, can be useful to develop effective strategies for sustainable management, especially in a scenario of increasing shortage of mineral phosphate resources. In this paper, we review the relationship of phosphate to iron oxides and organic matter, and its effect on phosphorus availability. Crops typically obtain phosphate from weathered minerals and dissolved fertilizers. However, the amount of phosphorus present in the soil solution depends on the extent to which it is adsorbed or desorbed by iron oxides, which may be influenced by interactions with organic matter. Therefore, systems for fertilizer recomendation based on methodologies considering interactions between soil components such as oxides and organic matter, and the phosphorus sorption capacity resulting from such interactions (e.g. residual P analysis), may be more reliable to ensure efficient, rational use of phosphate.

Intercropping may be a strategy for phytoremediation of vineyard soils with high copper (Cu) content. The study aimed to evaluate the contribution of South American native grasses in limiting Cu availability and toxicity in soils grown with grapevines. The soil used in the experiment was collected in natural grassland with no history of cultivation. The samples were air-dried; acidity, P and K levels were corrected and samples were then incubated. We used three Cu levels - natural content (Dose 0) and the addition of 40 and 80 mg Cu kg-1 of soil (Dose 40 and 80). At each Cu dose, grapevine was grown in three cropping treatments: monocropping, intercropping with Paspalum plicatulum and intercropping with Axonopus affinis. In intercropping, two grass seedlings were transplanted into each experimental unit 35 days prior to the transplanting of the grapevines. The soil solution was sampled and ionic speciation was carried out. At 70 days after planting, we sampled the grapevines to determine dry matter, morphological parameters and nutrient concentration in the roots and shoots. Intercropping young grapevines with Paspalum plicatulum and Axonopus affinis was efficient in promoting the growth of young grapevines at moderate and low levels of Cu contamination by reducing Cu bioavailability. This indicates that maintaining native grasses in young vineyards is an effective strategy for phytoremediating Cu-contaminated soils and obtaining a grape production system with reduced interventions in the native environment, in addition to contributing to soil protection and nutrient cycling.