Availability of Nitrogen and Other Nutrients on Four Fertilized Range Sites during the Active Growing Season

Abstract

The course of available soil nitrogen, phosphorus, potassium, and water were followed during the 1964-1969 growing seasons on four range sites in western North Dakota. Available nitrogen and potassium demonstrated regular high and low peaks of availability on three of the four sites studied. Available soil water does not appear to be the major factor in determinging the time and magnitude of the cyclic phenomena; rather differences in site characteristics play a greater role. Phosphorus showed little fluctuation throughout the growing season. The magnitude of the fluctuations between high and low points represents between 25 and 50% of the amount present with respect to nitrogen and potassium. The timing of the fluctuations is associated with major phenological events of the native vegetation on each site. Lag periods of about 15 days were observed between the 0-6 and 12-24 inch soil depths in nutrient availability. A consideration of the major periods and characteristics of activity and range site with respect to available soil nutrients is necessary to realize optimum production from native rangeland soils ecosystems.