Utilization of Biomass and Forage Crops to Remediate P-Impacted Soils in Florida.

Florida soils are particularly susceptible to P leaching due their sandy texture, low P retention capacities, and fluctuating water tables. Phytoremediation, defined as the use of plants for in-situ remediation of contaminated soils, represents a potential environmentally sound alternative to reduce P transport from manure-impacted soils. Limited research has been conducted on the potential benefits of utilizing forage crops for both minimizing the environmental problems associated with excess P and the associated benefits of biomass production. The objectives of this study were to (i) screen an array of forage crops for their P removal capacity potential, and (ii) investigate the impacts of forage P uptake on soil P concentrations and water quality. The 2-yr study included fifteen forage cultivars cultivated on a commercial dairy farm that had been continuously grazed for over 50 yr. Forage was periodically harvested to determine DM yields and tissue N and P concentrations. Plots received 80 kg N ha^-1 after every harvest. Soil samples were collected annually from Ap, E, and Bh horizons. Two suction lysimeters were installed at 60 and 90 cm depth to monitor P concentrations above and below the Bh horizon, respectively. Dry matter yields varied considerably among the various species. Elephantgrass and sugarcane yielded significantly more than the other species tested. The greatest P uptake and P removal values were observed in the elephantgrass plots. Soil P concentrations in the Ap horizon were reduced in response to P uptake, however no differences were observed in the E and Bh horizons. No differences in P concentrations in the groundwater were observed among the treatments, possibly due the short duration of the study. Despite some limitations, such as the need for high N rates, phytoremediation using forage crops can be a feasible alternative to reduce the risks of P transport from manure-impacted soils.