The elephant grass BRS Capiaçu is a new cultivar in the forage area, having a productive potential both in the form of silage and in the form of green chopped. However, for its planting and maintenance, the cultivar requires a soil with good fertility, especially with phosphorus requirements for good development in the initial establishment phase. The objective of this research was to evaluate the initial development of the BRS Capiaçu cultivar (Pennisetum purpureum Schum.) submitted to different levels of phosphate fertilization. The experiment was developed between the months of October/2022 and January 2023, in the Vitrine of Technologies of Embrapa, located in the Agricultural Exposition Park “Luiz Lorenço de Souza”, in the municipality of Parintins - AM. It was conducted in plastic bags with 10 kg of soil, packed in field conditions. The soil used was collected in the Vitrine area, where a chemical analysis was performed to determine the amount of lime to be added to raise the base saturation to 55% and the amount of phosphorus in the soil to define the phosphorus levels to be used. The experimental design adopted was entirely randomized (DIC), with five levels of P2O5 (0, 15, 30, 45 and 60 mg/dm³) with fourteen repetitions, totaling 70 sampling units. Thirty days after planting, the following response variables were analyzed aboveground fresh mass (MFPA), root fresh mass (MFR), aboveground dry mass (MSPA), root dry mass (MSR), MFPA/MFR and MSPA/MSR ratios, root length (CR), aboveground length (CPA), thatch length (CC), After the measurements, the plant material was taken to an oven at 55 º C for 72 hours to determine the dry mass of the aboveground part (MSPA) and roots (MSR). In the analysis of variance, the PROC MIXED procedure of the statistical software SAS (Statistical Analysis System) was used and the Tukey test for multiple comparison of means, at 5% significance level. It was found that most variables analyzed showed better performance between levels 30 and 45 mg/dm³ of P2O5.
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