NON-NITROGEN NUTRIENT INPUTS AND OUTPUTS FOR FERTILIZED PASTURES IN SILT LOAM SOILS IN FOUR SMALL OHIO WATERSHEDS

Authors: Owens, Lloyd; VAN KEUREN, ROBERT - EMERITUS-OSU/OARDC; EDWARDS, WILLIAM - EMERITUS-USDA/ARS

Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2003
Publication Date: 4/12/2003
Citation: Owens, L.B., Van Keuren, R.W., Edwards, W.M. Non-nirogen nutrient inputs and outputs for fertilized pastures in silt loam soils in four small Ohio watersheds. Agriculture Ecosystems & Environment. 2003. v. 97. p. 117-130.

Interpretive Summary: In an effort to better understand and protect soil, water, and air quality, the impacts of agricultural practices on nutrient cycling needs to be known. Nitrogen is a macro-nutrient and has received much of the focus of nutrient studies. Although row crop agriculture has been in the forefront of environmental studies, grasslands are receiving increasing attention because of increasing interest in grazing systems. Realizing that nitrogen is not the only nutrient of importance and that perhaps other nutrients could have environmental impacts, this study looked at non-nitrogen nutrients in a grazing system. Cattle were rotated through 4 pastures during the summer and kept in one of the 4 during the winter with hay being brought into the feeding area. Nutrient inputs of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), and chlorine (Cl) were measured in rainfall, fertilizer and lime, hay, and salt/mineral blocks. Outputs of these nutrients (plus Total Organic Carbon, TOC) were determined in surface runoff and subsurface flow. In the summer only grazed pastures most of the nutrients were lost in subsurface flow, but losses were small. In the winter feeding area, hay was the major contributor of nutrients, especially P and K. While Ca, Mg, and Cl were lost predominantly in subsurface flow, P, K, and TOC were lost predominantly in surface runoff. For most of the nutrients, the outputs exceeded the inputs. The exceptions were P and K in the winter feeding area where inputs greatly exceeded outputs. Soil tests showed that both P and K were building up in the soil. Thus if hay is brought into a cattle feeding area for several consecutive years, a built up of soil P and K can occur and perhaps have detrimental impacts. This information is important to producers as well as the Natural Resources Conservation Services (NRCS) and Extension personnel who advise producers.

Technical Abstract: Budgets of non-nitrogen nutrients were studied in a rotational pasture system during two treatment periods, which received different levels of nitrogen (N) fertility. Although most nutrient budget studies from grasslands have focused solely or primarily on N, maintenance of a proper nutrient balance is important to healthy plant growth and reduction of potential water quality problems. Rotationally grazed grass pastures received 56 kg N/ha as NH4NO3 for a 5-year period and then 168 kg N/ha for a 10-year period. A topsoil pH of 6.0 and available P and K levels of 28 and 168 kg/ha, respectively, were maintained. Cattle grazed four paddocks during the summer and were fed hay in one of the paddocks during the winter. Inputs of P, K, Ca, Mg, Na, and Cl from precipitation, fertilizer, and hay were determined. Losses of these nutrients plus TOC were measured in surface runoff and in water from springs draining each area. The majority of the nutrients from the summer only grazed paddocks (SG) were transported in subsurface flow. Hay was the major source of P and K in the winter feeding/summer grazing paddock (WF/SG), and surface runoff was the major transport pathway for them and TOC. Most of the transport of Ca, Mg, Na, and Cl from the WF/SG area occurred via subsurface flow. Concentrations of P in subsurface flow were low; Na concentrations changed little during the 15-year study; Mg, Ca, and Cl concentrations increased slowly from the SG area but much more rapidly from the WF/SG area. Pasture systems where nutrient balances are maintained have little possibility of detrimental environmental impacts. When large amount of nutrients are brought into an area with hay, there can be a soil buildup of P and K. This increases the possibility for adverse water quality impacts.