Effect of Pasture Management on Soil Solution Nitrate-N Content and Water Quality

Livestock husbandry has a significant impact on ecosystem components and nutrient cycling. The lack of soil disturbance associated with pasture/range livestock farms is considered to be accountable for improvements such as erosion reduction, good soil quality and more plant-available water. However, the grazing animals might have a negative effect on the environment by creating higher level of nitrogen in soil and adjacent waters. This study was conducted to assess nitrate-N content in soil solution of a pasture system in North Florida. The field experiment consisted of 12 pasture-plots designed in complete randomized block with three grazing treatments. A tension lysimeter technique was used for soil solution samples collection. Following the randomized design, i.e. three replicates by depth of 61, 122, and 183 cm for the two contrasting graze-treatments, a total number of 18 suction cup lysimeters were assigned on six 0.81-ha pasture plots. Soil solution samples were taken biweekly, analyzed for pH, EC, NO 3-N, and monthly data averaged as one aggregate observation per plot at each depth. The study showed that suction lysimeter technique can be used in livestock husbandry monitoring. The results indicated that grazing and sampling time appeared as significant (P<0.001) factors in the soil solutions pH, EC, and NO 3-N content. Although a downward NO 3-N migration was observed, the nitrate-N concentrations were close to the maximum permissible level (MPL) for US drinking water. The study also confirmed the effect of biosolids-derived nutrients demonstrating lower NO 3-N concentrations in soil solution to the depth of 122 cm in the plots where double rate biosolids was applied.