Effects of pasture-applied biosolids on forage and soil concentrations over a grazing season in North Florida. I. Macrominerals, crude protein, and in vitro digestibility

The rationale for this experiment was to determine forage nutrient concentr ations as affected by biosolids fertilization. We studied the effects of si ngle applications of two exceptional quality biosolids to bahiagrass (Paspa lum notatum) pasture with regard to satisfying beef cattle nutrient require ments. Twenty-five 0.8-ha pastures were divided into five blocks. Two bioso lids were applied as normal and double agronomic rates. The control plot re ceived NH4NO3. Forages were analyzed for calcium (Ca), phosphorus (P), magn esium (Mg), potassium (K), sodium (Na), crude protein (CP), and in vitro or ganic matter digestibility (IVOMD), and soils were analyzed for Mehlich I e xtractable Ca, P, Mg, and K. Single (agronomic or twice this) applications of biosolids to pastures had little effect on Ca, P, Na, and K forage conce ntrations, but forage Mg was elevated in several treatments late in the sea son. Crude protein concentrations were elevated above the control for all b iosolids treatments late in the season, whereas only small differences were observed at early sampling times. Trends were similar for IVOMD. In genera l, all treatments were associated with soils with adequate Ca, P, and Mg co ncentrations, while soil K was uniformly low. In relation to grazing beef c attle requirements, all treatments resulted in generally adequate forage le vels of Ca, P, Mg, K, CP, and IVOMD, however, Na (<0.06%) was deficient.