Sunflower Type Influences Yield Prediction using Active Optical Sensors

Active-optical (AO) sensors have been used in several crops as a yield-prediction tool for N management, but not in sunflower (Helianthus annuus). The need for in-season N and its rate can be determined through using a yield and AO relationship. By comparing predicted yield from an area of sufficient N to another area of the field, the yield difference multiplied by the N required for the additional yield results in the fertilizer N rate. This study was conducted to determine what parameters, including plant height and plant stand, would be most useful in relating AO sensor readings to sunflower yield. The experiments were conducted in 2015 and 2016 on a total of 20 locations in North Dakota. The experimental design was a split-plot randomized complete block, with six N rates as the main plot treatments and P rate (four in 2015 and two in 2016) as split plot treatment. Since P had no influence on yield, it was ignored in this study. The AO sensors were the GreenSeeker and Holland Crop Circle. The AO sensors were used when the sunflower was at the V6 and V12 growth stages. Manual height and an acoustic height sensor were used on most sites at the time of AO sensor readings. Sensor readings with and without consideration of crop height were subjected to regression analysis with crop yield. The AO sensor readings were related to confection sunflower yield, but not oilseed sunflower yield. Oilseed sunflower yield was most related to crop height.