PRECIPITATION NUTRIENT INPUTS IN SEMIARID ENVIRONMENTS

Seasonal and spatial variations in precipitation nutrient inputs were suggested by differences in storm type and air mass origin into southeastern Arizona. Wet precipitation NO3-N, NH4-N, PO4-P, and K inputs were collected at seven sites to determine seasonal and spatial variations in nutrient inputs. Total nutrient inputs and concentrations in summer precipitation were significantly greater than in winter precipitation. Higher summer total inputs and concentrations were attributed to storm type and air mass origin rather than precipitation amount, as summer precipitation accounted for 56% of the precipitation and 79, 69, 66, and 73% of the NO3-N, NH4-N, PO4-P, and K, respectively. Spatial variability in nutrient inputs was limited to specific nutrients, seasons, and sites and attributed to precipitation variability and localized sources. Generally, the air masses and storm types that produced seasonal differences in nutrient inputs and concentrations affected all sites uniformly.