The goal of this paper was to evaluate the interaction of phosphorus and
nitrogen fertilization, as well as availability and its performance in productivity of
Panicum maximum cv. Massai, availability in the soil, nutritional aspects, and ruminal
degradability, voluntary intake and tracking available phosphorus applied through
fertilization, animal mineralization and P cycling system in Quartzipsamment soil. The
experiment was conducted at EMVZ - UFT, in a randomized block, 2x2 factorial, using
P (50 and 200 kg ha-
¹ of P2O5) and N (100 and 400 kg ha-
¹ N) and control unfertilized
with four repetitions. The study area consisted of 32 paddocks each (301 m²), with
already established Panicum maximum cv. Massai pasture. The experimental area
was managed under intermittent stocking with variable stocking rate. It was used 28
mixed breed sheep for grazing management. Evaluations were made before and after
grazing regarding the agronomic and structural characteristics and productivity of
Massai grass, and soil chemical characteristics. Moreover, it was evaluated the
nutritional value of the forage including bromatological parameters, degradability and
intake, using titanium dioxide as an external indicator of consumption, and how much
it was able to modify animal biometrics. It was also evaluated the P balance in the
system which was estimated based on existing fractions in the soil, plant and animal,
and additions resulting from fertilization, mineralization by animals and P cycling in the
system. Both fertilizations temporarily modify the chemical characteristics of the soil,
increasing pH, Mg, P, V%. The layers from 0 to 10 cm achieved the highest values of
the base. Fertilization of P and N increase forage production and consequently provide
an increase in stocking rate. However, it is necessary to establish a fine adjustment
between the quality and quantity of forage produced and provided to sheep in order to
obtain the highest gain per area. Fertilization alters the nutritional quality of Panicum
maximum cv. Massai grass especially in high concentrations of P. Among the
nutritional parameters evaluated, fertilizations influence the NDF, grass digestibility
and voluntary intake by animals. Soluble phosphorus sources added have little residual
effect on Quartzipsamment soil. The destination and the possible mobility and
consequent loss of phosphorus in the soil-plant-animal system in Quartzipsamment
soil should be better studied in order to increase production efficiency. An installment
possibility of soluble phosphate fertilizer levels above 50 kg P2O5 ha-¹
is an alternative
to avoid P fertilization inefficiency in Quartzipsamment soil.
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