Remediation of nutrients runoff from feedlot by hydroponic treatment

Abstract

Nutrient runoff from feedlot can contaminate surface and groundwater and may cause eutrophication if not managed properly. In this study, a cost-effective and environmentally friendly hydroponic treatment was compared with the standard Hoagland solution for treating feedlot runoff and evaluating plant growth and nutrient removal under greenhouse conditions. The hydroponic remediation method was evaluated in batches using 10 L of feedlot runoff and Hoagland solution individually applied in a plastic tub planted with water hyacinth (Eichhornia crassipes), water lettuce (Postia stratiotes), and sorghum (Sorghum bicolor) separately. Water samples were collected weekly and plant biomass were collected at the beginning and the end of the experiment. The sorghum plants grown in the Hoagland solution produced 3.0 and 2.6 times higher biomass than the runoff in first and second batch experiment, respectively, due to balanced nutrient availability, especially nitrogen. Nutrients from the feedlot runoff and Hoagland solution were reduced by all plants as they uptake nutrients, but sorghum outperformed other plants. Plants grown in feedlot runoff, reduced >90% ammonium nitrogen (NH4-N) through the root absorption. Total phosphorus (TP) reduction by sorghum ranged 52%-92% from the Hoagland solution and 70%-100% from the feedlot runoff. Water hyacinth reduced TP by 61%-74% from the feedlot runoff, but only 9%-33% in the Hoagland solution. The TP reduction by water lettuce ranged 49%-93% from the feedlot runoff, but its reduction was not significant in the Hoagland solution. Water lettuce reduced significantly more (75%) Total Kjeldahl Nitrogen (TKN) from the undiluted feedlot runoff than the sorghum (61%) and water hyacinth (66%). Overall, sorghum outperformed water lettuce and water hyacinth by taking up more TP, NH4-N, nitrite and nitrate nitrogen (NO2-N+NO3-N), ortho-phosphorus (Ortho-OP), and potassium (K) from the undiluted feedlot runoff in both batch experiments.