Land use and land cover in critical source areas on small dairy farms in the eastern United States

Abstract

Rotational grazing (RG) is a livestock management practice that moves grazing cattle among small temporary pastures called paddocks. In dairy farming, RG has potential to improve soil and water conservation by situating well-managed perennial vegetation on erosion-prone parts of farm landscapes. Recently, geospatial technologies have enabled precise identification of “critical source areas” (CSAs). CSAs are sites where slope, soil, and water flow factors coincide to create the largest potential impacts on surface water quality from erosion within the landscape of a farm. Examination of land-use and land-cover (LULC) practices on CSAs allows nuanced comparisons of effects on water resources among agricultural production systems, enabling us to test the hypothesis that RG dairy farms manage CSAs so as to have lesser effects on water resources than comparable-sized nongrazing dairy farms. We assessed LULC on CSAs in 53 small dairy farms in New York, Pennsylvania, and Wisconsin, United States, using satellite imagery and other spatial data. Among these farms, 22 used some form of RG, while the remainder did not use grazing. We also did on-farm observations of most CSAs to assess the frequency of features that may particularly affect water resources, such as unvegetated areas within pastures. RG dairy farms differed significantly from nongrazing dairy farms in the total allocation of CSA area to hayfields and rotational pastures—two LULC types that are likely to reduce runoff and emissions of sediment and nutrients into waterways—but this difference varied across the states and was pronounced only in the Pennsylvania farms, where high-intensity grazing farms allocated these perennial LULC types to over 60% of CSA lands, while nongrazing farms allocated these LULC types to about 20% of CSAs. In New York and Pennsylvania, RG farms allocated significantly less erosion-prone annual cropland to CSA sites than nongrazing farms, and allocated less of the total farm area to LULC practices that are relatively vulnerable to soil erosion. However, these differences between farm types were pronounced only in Pennsylvania farms. Our results do not support the hypothesis that RG dairy farms are generally superior to comparably sized nongrazing dairy farms in their management of CSAs. It is likely that targeted technical and cost-share support could improve management of CSAs in RG farms, allowing them to more fully realize the potential of RG systems to improve soil and water conservation.