Effect of cover crops on phosphorus and trace metal leaching in agricultural soils

Authors: SANDU, VISHAWJOT - Auburn University; LAMBA, JASMEET - Auburn University; KAUR, PREETIKA - University Of Wyoming; MALHOTRA, KRITIKA - University Of Southern California; Way, Thomas; Balkcom, Kipling; PRASAD, RISHI - Auburn University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2025
Publication Date: 2/8/2025
Citation: Sandu, V., Lamba, J., Kaur, P., Malhotra, K., Way, T.R., Balkcom, K.S., Prasad, R. 2025. Effect of cover crops on phosphorus and trace metal leaching in agricultural soils. Agricultural Water Management. 309:109343. https://doi.org/10.1016/j.agwat.2025.109343.
DOI: https://doi.org/10.1016/j.agwat.2025.109343

Interpretive Summary: Manure from broiler chickens contains phosphorus (P), and may contain small amounts of zinc (Zn), copper (Cu), and nickel (Ni). Rainfall can transport these elements off the soil surface in surface runoff water or down into the soil profile through leaching. Cylindrical soil cores, 15 cm diameter and 50 cm depth, were collected from the loamy sand soil of a cotton field in east central Alabama. We simulated rainfall by irrigating the soil surface of each core, and leachate water was collected after it flowed down through each soil core. The results showed preferential flow in the cores due to the presence of macropores. Cover crops are useful as effective soil management practices to enhance soil health. Concentrations of total P, colloidal P, and dissolved P in the leachate water were significantly greater from cover crop soil cores fertilized on the soil surface with poultry litter (a solid mixture of manure and a bedding material), than from cores from a no cover crop field area which were fertilized with poultry litter. Similar trends were observed in trace metal losses. The preferential flow through soil macropores increased the mobility and velocity of solute movement in this cover cropping system.

Technical Abstract: Our objective was to determine the effect of cover crops on total phosphorus (TP), colloidal P (CP), dissolved reactive P (DRP), dissolved P (DP), total metals, dissolved metals, and colloidal metals in leachate water from loamy sand soil cores. The cover crop, a mixture of cereal rye and crimson clover, was planted in the late fall in the field. The main crop, planted the following spring, was strip-tillage cotton. Following cotton harvest, intact undisturbed cylindrical soil cores (15 cm diameter and 50 cm depth) were collected from cover crop (CC) and no cover (NC) parts of the field. In the laboratory, for half of the leachate trials with the CC soil cores, we broadcast-applied poultry litter on the soil surface of the cores using a 10 Mg/ha litter application rate, and for the other half of the trials with the CC cores, no litter was applied. For half of the trials with the NC soil cores, we broadcast-applied poultry litter on the soil surface of the cores at 10 Mg/ha, and for the other half of the trials with the NC cores, no litter was applied. We simulated rainfall by irrigating the soil surface of each core, and leachate water was collected after it flowed down through each soil core. The leachates collected during the rainfall simulations were analyzed for TP, CP, DRP, DP, total metals, dissolved metals, and colloidal metals. The metals were Zn, Cu, and Ni. The results showed preferential flow in the cores due to the presence of macropores. The TP, CP, and DP concentrations were significantly greater from CC cores fertilized with poultry litter, than from NC cores fertilized with poultry litter. Similar trends were observed in trace metal losses. The preferential flow through soil macropores increased the mobility and velocity of solute movement in this cover cropping system.