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SOIL & WATER MANAGEMENT & CONSERVATION

Electromagnetic Induction Sensor Data to Identify Areas of Manure Accumulation on a Feedlot Surface

^a USDA-ARS, U.S. Meat Animal Research Center, P.O. Box 166, Clay Center, NE 68933
^b Dep. of Environmental Science, Univ. of California, Riverside, CA 92521
^c USDA-ARS, Agroecosystem Management Unit, 104 Chase Hall, Univ. of Nebraska, East Campus, Lincoln, NE 68583

^* Corresponding author (bryan.woodbury{at}ars.usda.gov).

A study was initiated to test the validity of using electromagnetic induction (EMI) survey data, a prediction-based sampling strategy, and ordinary linear regression modeling to predict spatially variable feedlot surface manure accumulation. A 30- by 60-m feedlot pen with a central mound was selected for this study. A Dualem-1S EMI meter (Dualem Inc., Milton, ON, Canada) pulled on 2-m spacing was used to collect feedlot surface apparent electrical conductivity (EC_a) data. Meter data were combined with global positioning system coordinates at a rate of five readings per second. Two 20-site sampling approaches were used to determine the validity of using EMI data for prediction-based sampling. Soil samples were analyzed for volatile solids (VS), total N (TN), total P (TP), and Cl^–. A stratified random sampling (SRS) approach (n = 20) was used as an independent set to test models estimated from the prediction-based (n = 20) response surface sample design (RSSD). The RSSD sampling plan demonstrated better design optimality criteria than the SRS approach. Excellent correlations between the EMI data and the ln(Cl^–), TN, TP, and VS soil properties suggest that it can be used to map spatially variable manure accumulations. Each model was capable of explaining >90% of the constituent sample variations. Fitted models were used to estimate average manure accumulation and predict spatial variations. The corresponding prediction maps show a pronounced pen design effect on manure accumulation. This technique enables researchers to develop precision practices to mitigate environmental contamination from beef feedlots.

Abbreviations: EC_a, apparent electrical conductivity • EMI, electromagnetic induction • GPS, global positioning system • LR, linear regression • RSSD, response surface sampling design • SRS, stratified random sampling • TN, total nitrogen • TP, total phosphorus • VS, volatile solids