Nutrient removal by grass components of vegetated buffer systems receiving swine lagoon effluent

ABSTRACT:

Information is needed on nutrient removal mechanisms in vegetated buffer systems to assist in the design of these long-term nutrient removal systems. We determined nutrient removal by grass portions of grass-forest buffer systems receiving swine lagoon wastewater. Cuttings were made at three positions within buffers of coastal Bermuda grass (Cynondon dactyion L.) (Tifton 78) for three years. Wastewater was applied weekly at two rates. The first rate averaged 800 kg N ha⁻¹ yr⁻¹ (714 lb N ac⁻¹ yr⁻¹), 215 kg P ha⁻¹ yr⁻¹ (192 lb P ac⁻¹ yr⁻¹), and 1030 kg K ha⁻¹ yr⁻¹ (920 lb K ac⁻¹ yr⁻¹), and the second rate furnished twice these amounts. Grass buffers 20 m (65.6 ft) in length removed 44% of the nitrogen (N), 19% of the phosphorus (P), and 23% of the potassium (K) as grass biomass from the lesser wastewater application rate. Nutrient removal via uptake (percentage of applied) dropped by a factor of 1.6 when wastewater was applied at the greater rate. Overall, the study showed that while nutrient uptake into the grass biomass accounts for a portion of the nutrient removal in grass-forest buffer systems, the nutrient concentrations in surface runoff and subsurface water exiting these systems as reported previously (Hubbard et al., 1998b), imply that other factors (denitrificntion, forest uptake, and adsorption) play a greater role in the nutrient assimilation and filtering commonly associated with grass-forest buffer systems. The information on biomass production and nutrient removal by coastal Bermuda grass receiving wastewater in a lower landscape position is important for producers who want to utilize the wastewater nutrients and produce forage on an under-utilized poition of the landscape.