Sugar Beet Yield and Quality Prediction at Multiple Harvest Dates Using Active-Optical Sensors

Yield prediction in sugar beet (Beta vulgaris L.) is important as a basis for in-season N application. Active optical sensors have been researched in sugar beet for yield estimation. A common field method for using active-optical sensors is to establish an N non-limiting area, and compare the yield predicted from sensor readings with readings from the rest of the field. Yield difference is the basis for calculation of N rate. Sugar beet gains root mass and sugar content with time. The objectives of these experiments were to utilize two active-optical sensors at two timings with canopy height measurements and relate readings to root yield and recoverable sugar yield at consecutive harvest dates. A 2-yr study in the Red River Valley of North Dakota and Minnesota was conducted on four sites to compare two active-optical sensors, GreenSeeker and Holland Crop Circle, red normalized differential vegetative index (NDVI), red edge NDVI, with and without canopy height for use in sugar beet yield prediction. The red NDVI and red edge NDVI, used at V 6-8 and V 12-14 were similar in their relationship to sugar beet yield over several harvest dates. The r(2) of sensor measurement and yield relationships at V 6-8 improved when canopy height was considered but not at V 12-14. Active-optical sensors when canopy height is considered could be used to predict sugar beet root yield and recoverable sugar yield over a range of harvest dates, which would be useful in developing algorithms for in-season N fertilization.