Use of Active Optical Sensor in North Dakota Dave Franzen and Lakesh Sharma, North Dakota State University, Fargo, ND

Use of active optical sensors is limited, due to short and rainfall-uncertain time-frame of spring wheat post-N application and limited practical application in regional winter wheat

From planting to harvest of spring wheat is typically 90 days. An application of yield-enhancing post-N application would need to be accomplished during a 10-day window It might or might not rain after application

Failure to apply preplant N can result in early tillering and root development that reduces yield (Ashley, Dickinson, ND, 2008)

Exception would post-anthesis N. Can sensor readings at flag-leaf predict the need for post-anthesis N? On-going research at NDSU by Amanda Schoch (Dr. Joel Ransom) and Honggang Bu

Iron deficiency affects at least 500,000 acres in North Dakota. The Greenseeker has been used successfully by Dr. Goos and his students in screening varieties and rating amendments.

Sugarbeet tops as an N credit to subsequent crops

Possible improvement in process- better biomass estimation- ComparisonNDVI NDVI X Canopy height r r Dry matter N content Total N

Two recent papers (Yin et al., 2011a&b) have related early corn height to final yield.

13 corn N rate trials were established and taken to yield in Each trial- 6 treatments, 4 blocks, RCB N treatments- check, 44, 88, 132, 176, 220 kg N ha -1 as ammonium nitrate before planting

Greenseeker and Crop Circle sensor was used to gather readings at corn- 6-8 leaf stage Corn leaf stage (about 2 weeks after 1 st ) Height measurement was made the same time as the sensor reading using a tape measure. One measurement was recorded from each plot.

INSEY was determined using both sensors using reading/growing degree days or (reading X height cm)/growing degree days

Summary- Greenseeker sensor has been used successfully in soybean for IDC screening and in sugarbeet. Use of sensors for in-season N application in spring grains has not been supported due to practical application concerns. Ongoing research is being conducted to direct post-anthesis protein enhancement of spring wheat INSEY relationships were constructed with both the Greenseeker and Crop Circle sensors in corn. Multiplying INSEY by the corn height increased the relationship with yield with the Greenseeker at the 6-8 leaf stage and the leaf stage and the Crop Circle at the 6-8 leaf stage. Corn height reduced the relationship of the Crop Circle with yield at the leaf stage.