This study compared the residual effect of reactive natural phosphate originated from Morocco with that of triple superphosphate on the oat biomass production, soybean yield and yield components, availability of phosphorus and sulfur in the soil and determined these nutrient contents in soybean leaf tissue in response to the phosphorus and sulfur sources and doses. The study consisted of soybean and oat crops cultivated under minimum tillage cultivation system. The experiment had a complete randomized block design with four replications and the treatments arranged in a 2 x 4 x 3 factorial design with two phosphate fertilizers, reactive natural phosphate (RNP) and triple superphosphate (TSP), with four rates of each fertilizer (0, 100, 200 and 300 kg ha-1 of P2O5) respectively, and three rates of sulfur (0, 30 and 60 kg ha-1 elemental S). The phosphorus and sulfur content was evaluated in the leaf tissue. Available phosphorus in the soil was evaluated at depths of 0-10 and 10-20 cm. Results indicate that in the first year the triple superphosphate source did not perform better than the reactive natural phosphate source regarding the productivity and mass of 100 grains. The TSP application led to increasing P concentrations in the leaf tissue, but there was no effect of the application of increasing RNP doses on the leaf phosphorus concentration. The S concentration in the leaf tissue increased in response to the higher phosphorus and sulfur doses as TSP and RNT fertilizers.
phosphate fertilization; phosphate efficiency; Glycine max (L) Merrill
