ABSTRACT
Excessive levels of soil potassium (K) can lead to increased concentration of K in forages, causing metabolic disorders in ruminants, especially in pre-parturition cows and heifers.  Composite soil samples (15 to 20 cores) were taken from pastures on five farms in the northeast USA: two farms in Pennsylvania (PA1 and PA2, one dairy, one beef), two farms in New York (NY1 and NY2, dairies), and one farm in Maryland (MD1, organic dairy) over a two year period. Soil samples were taken at 0-2 inch and 0-6 inch depths within paddocks where animals had concentrated, causing soil degradation due to excessive hoof traffic (‘Concentrated’ = ‘C’). Corresponding samples were taken within the same paddock to represent vegetated areas containing normal plant growth (‘Open’ = ‘O’).  Variations in location and size of C areas in any given paddock occurred due to changes in grazing practices, climatic conditions, and changes in paddock utilization for supplemental feeding.  Corresponding soil samples from C and O areas showed that 93% and 66%, respectively, of all soil samples across all farms were considered to have “excessive” K levels (>200 ppm soil K, Mehlich-3 extraction method) for perennial forage crop requirements.  When considering depth of soil samples, 87% and 72% of all 2 inch and 6 inch depth samples, respectively, were found to have excessive levels of K. Applying the Pasture Condition Score (PCS) system to individual paddocks and their corresponding uses revealed that paddocks used for heifers and dry cows, or for wintering livestock, had lower PCS values than other pastures due to higher stocking densities and longer grazing periods.  These practices, coupled with a majority of paddocks containing excessive soil K levels, may contribute to increased animal health problems and reduced profitability of grazing-based operations in the region.