The objective of this experiment was to evalute the effects of phosphorus sources (Yoorin®, Ordinary Superphosphate (SS) + Triple Superphosphate (TS) and control) on the concentration and amount of N, P, K, and Ca in the excreta of crossbred steers under grazing conditions on mombaça grass (Panicum maximum Jacq. cv. mombaça) pasture. The grazing method was the continuous stocking with variable stocking rate, and the animals used were crossbred with average live weight of 300 kg. It was used a complete randomized design in split plot with four replications. Urine production and K concentration were high for animals grazing on Yoorin fertilized pastures compared to other treatments; urine production ranged from 7.2 to 20.4 L/animal/day and K urine concentration ranged from 180 to 310 g/L. Animals grazing on the control and SS + TS treatments presented greater N and P urine concentration than the ones grazing on Yoorin fertilized pastures, ranging from 154 to 195 g N/L and 0.2 to 0.29 g P/L, respectively. Average N and K amount excreted via urine was greater for animals grazing on Yoorin and SS + TS treatments compared to control treatment, ranging from 51 to 99 g N/animal/dia and 46 to 49 g K/animal/dia, respectively. Average Ca concentration and P and Ca amount excreted via urine were similar among treatments. Average fecal production and N, K, Ca concentrations and amounts were similar among treatments. Average P amount was greater for SS + TS and Yoorin treatments compared to the control, ranging from 7.5 to 11.6 g P/animal/day. Nutrient return via animal excreta contributed in the experimental period with 73, 87, 6, and 28 kg/ha of N, K, P, and Ca, respectively. Animals on Yoorin fertilized pastures presented greater urine production and greater K urine concentration and amount.
feces; macronutrient; phophorus; urine
