David W. Franzen, North Dakota State University, Fargo, ND, Honggang Bu, Soils, North Dakota State University, Fargo, ND and Lakesh Sharma, Cooperative Extension, University of Florida, Gaineville, FL
A series of nitrogen rate experiments were established in sugar beet (Beta vulgaris, L), sunflower (Helianthus annuus, L), and spring wheat (Triticum aestivum, L) in 2012. Two active-optical sensors were used in sugar beet and sunflower at the 6 leaf stage and again about two weeks after the first reading. The sensors were used at flag leaf (Zadoks 37) in spring wheat. Sensor readings were related to sugar beet yield and recoverable sugar per acre. Sensor readings were related to both confection and oil sunflower yield. The ratio of sensor readings at high N rates and the sensor ratio when the grain protein level was 140 g kg-1 was about 0.95 at two sites using two different spring wheat cultivars. Use of active optical sensors may be useful not only in yield prediction, but also certain quality parameters associated with nitrogen nutrition.