Spatial Soil Nutrient–Plant–Herbivore Linkages: A Case Study from Two Poultry Litter–Amended Pastures in Northwest Arkansas

Abstract

Core Ideas Analysis of soils and forages across landscapes aids in targeted nutrient management. Soil and plant relationships were identified on two beef farms and spatial scales. Higher soil nutrients favored bermudagrass growth compared with tall fescue. Grid sampling size impacts soil test values and site management. Feeding and grazing strategies affect nutrient excretion and nutrient loss spatially. Analysis of soils, forages, and landscapes can aid in targeting management of poultry litter and forage practices consistent with livestock production and water quality goals in watersheds with nutrient imbalances, such as in pastures of northwestern Arkansas. Objectives were to describe spatial relationships of soil and plant characteristics in litter‐amended pastures on two beef cow–calf farms in northwestern Arkansas. Fields were grid‐sampled for standing biomass, ground cover, soil nutrients, and vegetative composition at two sampling scales (14 and 60 m grids) for correlation analyses. Pearson correlation coefficients were used to identify relationships between soil and forage spatially and at two scales. For both scales on Farm A, positive correlations were found among exchangeable K, Ca, and Mg with organic matter. Correlations between pairs of soil variables were likely due to accumulated litter‐derived nutrients. Bermudagrass [Cynodon dactylon (L.) Pers.] cover was positively correlated with soil test P, dissolved reactive P, and K for the 14‐m sampling grid on Farm A, whereas tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] cover was negatively correlated with those soil variables on Farm B. This suggests that higher soil nutrient accumulations favored bermudagrass growth. Feeding and grazing strategies influence the amount and spatial pattern of nutrient excretion, which, in turn, affect the risk of nutrient loss and fertilizer requirements. These results document the influence of grid sampling size on soil test values for site management. Future GIS‐based studies will identify forage, soil, and terrain attributes in relation to P index mapping.