Simulated Runoff Nitrogen and Phosphorus Data

Simulated runoff procured in field plots across three different cover crop treatments, using Cornell Infiltrometer Rainfall Simulator. NO3-N, NH4-N, PO4-P, and TN were measured to investigate the nutrient capture effectiveness of each of the cover crop treatments.

This data set contains NO3-N, NH4-N, PO4-P, and Total Nitrogen (TN) concentration (mg/L) measurements from liquid runoff samples collected after simulated precipitation events. The runoff analyzed in this dataset was collected in Beltsville, MD at the Central Maryland Research and Education Center (CMREC) (39°00'46.0"N 76°49'35.7"W). Cornell sprinkler infiltrometers were utilized to generate simulated rainfall and runoff during December 2022 to April 2023 on two fields with contrasting soils. The first field, denoted “7E”, was a silt loam to silty clay loam with somewhat poorly drained soil and Russett-Christiana Complex soil map unit (lat 39.027207, lon -76.837643). The second field, denoted “39A”, was less than a mile away from the first field. This field was a sandy loam to loamy sand with excessively drained soil and Downer-Hammonton Complex soil map unit (lat 39.011941,lon -76.831742). During each sampling event five liters of runoff were collected as well as one liter of the deionized water used to create the “rain”, which was to be analyzed as a control in the nutrient analysis. The runoff collection was part of a greater experiment utilizing three different cover crop treatments (No Cover, 3-Way, and Rye) in two different cash crop residues (Corn and Soybean). Across the two field locations there were 36 sample locations spread evenly across cash crop residue and cover crop type. At each sample location 5L of runoff were collected and brought back to the lab at the University of Maryland College Park. A 45mL sub-sample of each liter of runoff collected was filtered using a 0.45μm membrane. After filtration the inorganic N concentrations, NO3-N and NH4-N, were determined colorimetrically using the Salicylate Method and the Endol Blue Method respectively. The inorganic P concentration, PO4-P, was determined using the Molybdate colorimetric test. The filtrate was also analyzed for the TN concentration by mixing the filtrate with a strong alkaline persulfate solution and heating the mixture for 1hr at 120 deg C under 16kpa in an autoclave. Following this, the mixture was analyzed for NO3-N and using the Salicylate Method, giving the total dissolved N concentration. All colorimetric analysis was performed using a DU 7000 Series Beckman Coulter Spectrophotometer and absorbance readings were converted into concentration (mg/L) using equations derived from the standard curves. 

NO3-N (mg/L) = 135.5*absorbance

NH4-N (mg/L) = 55.7*absorbance

TN (mg/L) = 146.7*absorbance - 1.447

PO4-P (mg/L) = 1.764*absorbance + 0.007

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