Long‐term phosphate fertilization strategies evaluation in a Brazilian Oxisol

There are concerns related to the application of phosphate fertilizers to weathered soils that present low soil test phosphorus (STP) due to P adsorption in iron oxyhydroxides. Furthermore, long‐term trials are needed to evaluate crop response to corrective P fertilization and its interaction with different maintenance P fertilization strategies in these soils. An experiment involving the combination of three initial corrective P fertilization schemes (control without P correction or with the application of 105 kg P ha−1 as triple superphosphate [TSP] or reactive rock phosphate [RRP]), four P maintenance strategies (a control without the application of maintenance P, or 35 kg P ha−1 yr−1 as TSP, RRP, or a mix of both) and two application methods was cultivated during 16 yr at the Embrapa Cerrados experimental station in Planaltina, DF, Brazil. Corrective P fertilization promoted an early crop yield response. In contrast, high crop yields were only obtained in control treatments with no corrective P fertilization after soil P stocks were increased to a minimum level. With increasing P stocks, broadcast application resulted in slightly better yields. The required residual P stocks in soil to obtain high yields were estimated as equivalent to 113.6 and 205.2 kg P ha−1 for TSP and RRP, respectively. These values allow for STP contents to increase to critical levels, whose value for TSP of 4.1 mg kg−1 Mehlich‐1 P is below that recommended for the region, possibly due to the contribution of organic P forms in the long‐term no‐tillage system.