Managing Cow-Calf Operations: Implication to Nitrogen and Phosphorus Levels In Surface and Ground Water.

As animal-based agriculture has evolved to a larger production in subtropical region of United States, the problems associated with manure handling, storage and disposal have grown significantly. Despite substantial measurements using both laboratory and field techniques, little is known about the spatial and temporal variability of nitrogen and phosphorus dynamics across the entire landscape, especially in agricultural landscapes with cow-calf operations. Characterizing how nutrients vary across pastures is important for understanding how soil nutrients availability is controlling net primary productivity. Our results indicate that current pasture management systems which include cattle rotation in terms of grazing days and current fertilizer application (inorganic + manure + urine) for bahiagrass pastures in subtropical climates on loamy sand soils offer little potential for negatively impacting the environment. Properly managed livestock operations contribute negligible loads of nitrogen and phosphorus to shallow groundwater and surface water. Water quality in lakes associated with cattle production was “good” (30-46 TSI) based upon the Florida Water Quality Standard. Our results indicate that current cattle rotation and current fertilizer application offer little potential for negatively affecting the environment. A major research area that relates to the pathways and rates of movement of nitrogen and phosphorus deposited in urine and dung through various pools and back to the plants where knowledge is still lacking would be a potential focal point of our future investigations.