Temporal variability of soil property dynamics in a grazed pasture

The seasonal change in soil nutrients influences when producers can accurately sample fields for fertilization and compliance with environmental regulations. The objective of this study was to determine temporal variability of soil tests in a grazed pasture system. Soil samples were collected monthly from two different pastures analyzed for soil pH, plant-available nitrogen (NO₃-N), phosphorus (P), and potassium (K). Temporal variability did not exist for Mehlich 3 P and K during the study, but significant temporal variability was observed for the mobile nutrient NO₃-N during the study. Similarly, significant temporal variability was found for soil pH during the study, but the differences were rather small and probably would not affect management decisions. The results of our study indicate sampling time had no significant effect on plant-available P and K and a small but significant effect on soil pH, but this is very important for NO₃-N assessment when correct sampling protocols are followed.