Agronomic Efficiency Of Different Types Of LIME and Sources Of Phosphorus In Brazilian Cerrado SOILS Cultivated With Soybean.

<>With the increase in phosphate fertilizer prices, there is a need to find lower-cost alternatives that are as efficient as soluble sources like single (SSP) and triple superphosphate (TSP). To assess the efficiency of sources of P and two types of lime on soybean yield, an experiment was carried out with dystrophic Red Latosol (Oxisol). The experimental design was randomized blocks in a 2×3×4 factorial scheme, with four replicates. The treatments were: two types of lime [calcitic – CL (<5 dag kg^-1 of MgO) and dolomitic – DL (>13 dag kg^-1 of MgO)], three sources of P [triple superphosphate (TSP), ‘Yoorin' thermalphosphate (YT) and ‘Experimental' thermalphosphate (ET)], and four rates of P₂O₅ (0, 100, 200 and 300 kg ha^-1). The application of DL resulted in higher soybean yields than the application of CL. Two lime types influenced the pH, carbon (C), calcium (Ca) and magnesium (Mg) concentrations as well as the Ca/Mg, Ca/K and Mg/K ratios in the soil. With respect to sources of P, the YT applied in the soil with DL produced an agronomic efficiency index (AEI) similar to that of TSP, while in the soil with CL, the TSP, YT and ET were similar, with maximum technical efficiency (MTE) under both conditions starting at 230 kg ha^-1 of P₂O₅. The critical concentration of available P in the soil (Mehlich-1 extractant) for cultivation of soybean under the climate and soil conditions was between 5.0 and 6.0 mg kg^-1.