Eastern Virginia Agricultural Research and Extension Center

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Eastern Virginia Agricultural Research and Extension Center in Warsaw, Virginia

Located near Warsaw in Virginia's coastal plain, the Eastern Virginia Agricultural Research and Extension Center serves Virginia’s grain and soybean industries through research and educational programs leading to improved varieties and crop management practices. Research at the Eastern Virginia AREC supports the Virginia Tech small grain and soybean breeding programs, along with other research programs, that contribute to economically and environmentally sound crop production.

For some time now, we have emphasized using tiller density to determine if nitrogen applications are needed at Growth Stage 25 in wheat. Research published in Extension publications over several years advises that with a threshold of 50 to 100 tillers you don’t need to apply nitrogen at Growth Stage 25, but if your tiller count falls below 50 at that stage, nitrogen is needed.

In the past, handheld Normalized Differential Vegetative Index sensors have been used to collect the data on the greenness of plants and to determine how growth is progressing and the relationship to tiller count. With the advent of drones, we are looking to determine if aerial imagery can be used to help determine nitrogen rate and timing.

In 2017, we launched a study examining the relationship between tiller density and aerial NDVI collected with an unmanned aerial vehicle over several Virginia locations. Research reveals that NDVI data collected through drones recommends the same amount of Growth Stage 25 nitrogen as did tiller density. Both methods recommended applying 40 pounds of nitrogen at Growth Stage 25 if the tiller count was below 50. Therefore, there is no difference in yield on whether nitrogen is applied based on tiller density or NDVI.

This study shows us that aerial NDVI is a great proxy and it can be used to determine tiller density, so instead of having to go out and physically count tillers, you can fly your drone to collect your NDVI data. The next step in this research is to bring the studies to large scale farmer fields in Virginia. This stage of the study is currently on-going in 2022 and is being funded by the Virginia Agricultural Council. This will allow us to determine if the technology works large scale on the farm instead of just in small plots.