Learn how LAI, sap analysis and DGCI could benefit you
Life in the computer age means new high-tech ways to analyze your crop are constantly being devised. Here are three solutions that allow you to get a faster, more accurate handle on what your crop needs.
1. Leaf area index (LAI) measurement: LAI, which is a ratio of crop canopy to ground cover, indicates stress in a canopy. “It gives a really good indication of how much leaf area is being used for photosynthesis, which drives production,” says Rod Madsen, LI-COR Biosciences product manager. “For instance, look at soybeans during flowering stage. An open canopy at that stage is just wasting energy.”
Determining LAI can help farmers develop management practices to address the stress points on a plant that prevent the canopy from closing quickly. LI-COR has developed a plant canopy analyzer to take accurate LAI samples without resorting to crop description collection techniques, Madsen explains.
“Farmers are more in tune with technology,” he adds. “They want to understand the details about why small sections of a field aren’t producing and learn how to manage them differently.”
Using the FieldScout GreenIndex app on an iPad, Justin Strasberg, Nebraska-based Crop Tech Solutions, takes DGCI (dark green color index) samples.
2. Sap analysis: While tissue analysis shows what nutrients the plant has already used, sap analysis shows what the plant still has in reserve, notes Michelle Gregg, program director, Crop Health Laboratories.
“Tissue sampling is sort of like a post-mortem test,” she explains. “Sap analysis, however, carries the same
diagnostic value of a blood sample. The test provides a screenshot of the nutrient in the sap before it is metabolized by plant cells.”
Because of this, farmers can antici-pate crop needs and make fertility inputs before the plant even expresses deficiency symptoms, Gregg says. The tool has become increasingly popular in orchards, she says, but Crop Health Laboratories is able to sample sap from any row crop.
“Sap analysis has become the key component of my nutrient management program,” says Mike Omeg, an orchard grower in Washington. “Using this tool, I can adjust nutrient applications in real-time.”
3. DGCI analysis: You’ve heard of NDVI, but what about DGCI—dark green color index?
“The idea is to measure the subtle difference in greenness that your eyes can’t detect,” says Jacob Madden, director of marketing, Spectrum Technologies.
In the past, consultants have used a $2,000 gadget called a SPAD meter to get similar readings. Thanks to DGCI techno-logy, Spectrum has developed an iPhone and iPad app to correlate samples to SPAD readings for about a tenth of the cost. The FieldScout GreenIndex app costs $99.99, and users must purchase an additional color board for $49.
The board is colored green and yellow (to help balance out relative cloudy and sunny field conditions), bright pink (as a contrast tool) and gray (for white balance). Users place a corn leaf on the board and take a photo with their iPhone or iPad. Do this 20 or 30 times, and the app has enough information to calculate DGCI. Iowa State University and Penn State University have methods of calculating nitrogen needs based on DGCI readings.
“It’s not a be-all-end-all reading, but it’s a good guide for how much nitrogen to put down,” Madden says.
For more information about these new high-tech
crop diagnostic tools, visit www.FarmJournal.com/crop_diagnostics