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Title: Soil-surface nutrient distributions in grazed pastures of North Carolina

item Franzluebbers, Alan
item POORE, MATT - North Carolina State University
item FREEMAN, SHARON - North Carolina State University
item ROGERS, JOHNNY - North Carolina State University

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2019
Publication Date: 11/19/2019
Citation: Franzluebbers, A.J., Poore, M.H., Freeman, S.R., Rogers, J.R. 2019. Soil-surface nutrient distributions in grazed pastures of North Carolina. Journal of Soil and Water Conservation. 74:571-583.

Interpretive Summary: Efficiency of nutrient utilization on farms is increasingly of concern to farmers due to high cost of inputs and to stakeholders in the region due to potential negative environmental effects on water, air, and soil resources. A USDA-ARS scientist at the Plant Science Research Unit in Raleigh NC collaborated with the Amazing Grazing program at North Carolina State University to determine nutrient distribution on three North Carolina Department of Agriculture research-station farms associated with beef cattle grazing. On two of the three farms (10 to 65 acres each), large spatial variations in nutrients were detected among different zones of the farm. Zones of enrichment were often associated with repeated winter hay feeding in a particular location. Farmers may choose a designated feeding location due to convenience to access road and/or position on top of hills to avoid saturated conditions. Our results indicate that adoption of improved management approaches for grazing management could help reduce large variations in nutrient distribution and subsequent inefficient nutrient use on the farm. These results will help farmers to adopt better management approaches and help society to appreciate the challenges of sustainable livestock production to attain clean water.

Technical Abstract: Soil nutrient distribution in perennial pastures is likely affected by livestock activities, but detailed spatial patterns on a diversity of farms has not been widely investigated. Livestock management issues, such as placement of drinking water sources, fencing, placement of winter hay-feeding stations, and control of pasture access through seasonal stocking are key variables that could affect nutrient distribution despite attempts at uniform application of fertilizers. We sampled perennial pasture portions of three research-station farms in North Carolina on a 40-m grid in 2016. A total of 22 soil variables was measured including routine soil-testing of pH, cation exchange capacity, and extractable P, K, Ca, and Mg, as well as non-routine testing of sand concentration, total and particulate organic C and N, and soil-test biological activity. Large statistical variations in nearly all variables occurred within a location, leading to both severely deficient and heavily excessive levels of P and K on the same farm and sometimes on the same paddock. Soil-test biological activity and total soil N also varied spatially within locations. High nutrient concentrations were congregated in zones of several pastures, which could be related to historical and recent winter hay-feeding and permanent drinking-water locations. At the Piedmont location with recent winter hay-feeding, both organic and inorganic indicators generally corresponded to the same enrichment zones. At the Coastal Plain location with abandonment of a historical feeding location, divergences were observed between organic and inorganic indicators. Both organic and inorganic soil-testing indicators should be combined to make nutrient recommendations for better resource utilization. Livestock managers are encouraged to sample pastures in expected zones of nutrient differentiation so that nutrients can be used efficiently and environmental threats can be mitigated.