Integrated Evaluation of Multiple Inputs to Increase Soybean Yield in Nebraska (Part II): Evaluation of Crop Canopy Sensors As a Tool for Soybean Research and Production.

Determining the variables that consistently increase yields in soybean [Glycine max (L.) Merr.] continues to challenge researchers, agronomists and growers alike. Crop canopy sensors have emerged as a technology used in other cropping systems to monitor and manage agricultural inputs. The sensors measure reflectance in selected wavebands that are used to calculate vegetation indices that relate to unique leaf or canopy characteristics. The objectives of this study were to determine if a commercially available crop sensor could differentiate between seed treatments and foliar inputs and whether normalized difference red edge (NDRE) determinations during the growing season were significantly correlated with relative yield. Readings were taken with a RapidScan CS-45 Handheld NDVI Crop Scanner (Holland Scientific, Lincoln, NE) at four locations in eastern Nebraska during the 2014 cropping season. A factorial study was designed to evaluate five seed treatments (nontreated, fungicide, insecticide and fertility combinations), six foliar treatments (nontreated, fungicide, insecticide and fertility combinations) at pod set and two row spacings (38 and 76 cm) for a total of 60 treatments, replicated four times in a split-plot (row spacing, whole plots) alpha-lattice design. Readings were taken 12 times throughout the growing season, four between emergence and R3, and 8 times at weekly intervals after foliar treatments were applied at R3. NDRE values observed at R2 showed the greatest contrast between seed treatments with an 8% increase for the fungicide + insecticide + fertility seed treatment compared to the check. Differences in NDRE values for foliar treatments varied by location with the greatest increase, 11.6%, observed for the fungicide + insecticide treatment over the check at R7. Initial results indicate that the chosen sensor detected differences in plant response to both seed and foliar treatments at specific growth stages throughout the season.