Phosphorus has very low mobility into the soil, but in spite of this, it has been applied on the soil surface on some soil tillage systems. The efficiency of this form of application is not well known yet but can be affected by the soil pH and type of phosphate applied. This study aimed to assess the effect of the application method (mixed into the soil or on the surface, without incorporation) of phosphate fertilizers (diammonium phosphate, triple superphosphate, and ARAD rock phosphate), at two pH values (with and without lime), on some soil chemical characteristics and on corn dry matter yield. Corn plants were grown during 21 days after seed emergence in a growth chamber, in experimental units of 3.0 kg of soil (dry basis). In absence of liming (pH-H2O 4.7), addition of phosphates on the soil surface gave better yield and higher P uptake than their incorporation into the soil, and diammonium phosphate was the most efficient source. On limed soil (pH-H2O 5.7), there was no difference between the application methods, and the best yields were obtained with the soluble phosphate sources. Addition of phosphate fertilizers on the soil surface increased P in the soil up to 3 cm depth. In absence of water deficit, corn plants could obtain enough P from soluble phosphates added to the soil surface, despite their low mobility.
diammonium phosphate; triple superphosphate; ARAD rock phosphate; soil acidity; application methods