Nutrient Estimation Using Subsurface Sensing Methods.

This report investigates the use of precision management techniques for measuring soil conductivity on feedlot surfaces to estimate nutrient value for crop production.  An electromagnetic induction soil conductivity meter was used to collect apparent soil electrical conductivity (EC_a) from feedlot pens in Nebraska and Texas.  The EC_a from a Nebraska research feedlot was used by a program, ESAP, developed by the Soil Salinity Lab at Riverside, CA.  The program was used to direct soil sampling and develop regression models.  The soil sample data was analyzed for total nitrogen (TN) and total phosphorus (TP) then combined with the EC_a data to produce a correlation between EC_a and associated TP and TN (r² = 0.95, TP; r²=0.93, TN).    The calibration equations were used to estimate TP and TN across several pens (located in Texas and Nebraska).  Comparative values of the harvested nutrients give insights into management options for harvested manure.