Before you begin sampling in the field this season, do what you can to ensure you’re getting the best sample and making the most from your time spent.
“It’s very important to take a plant tissue sample from the correct plant part,” says Dr. Jim Friedericks, Outreach and Education Advisor for AgSource Laboratories. “For example, to have the earliest effect on this growing season, corn plants should be in the 8-leaf to 12-leaf stage, soybean plants can be submitted from 4-inches to 8-inches tall and alfalfa from 6-inches to first flowering.” These results can then be used to fine-tune an expected side-dress application or for a “rescue” nutrient application for the current crop.
The results from plant tissue samples are typically reported in comparison to the range of nutrient concentrations sufficient for that plant at that growth stage. Because these ranges shift with the growth of the plant it is important to identify the growth stage when submitting a plant sample to the laboratory. It’s normal for crop nutrient levels to vary throughout the season, therefore it’s important for these nutrients to be available when the crop needs them.
Alternatively, taking plant tissue samples multiple times throughout the growth cycle reveals the seasonal trends of your crop, and differences in your individual fields. Reports from these frequent plant tissue samples can be used to make corrections or additional nutrient applications as long as your field equipment makes it feasible to spray the canopy or dribble nutrients onto the soil surface.
Plant tissue sampling provides a picture of the nutritional status of your crops. Combined with a soil testing program, you can build a 360° view of your fields and crops to make better management decisions that could drive higher yields and reduce input costs throughout the growing season.
Plant tissue testing is also helpful when checking for suspected nutrient deficiencies. Often, a common visual sign of a macronutrient deficiency can be mistaken for what is actually micronutrient deficiency. One example is molybdenum (Mo), which is required for nodule formation in nitrogen fixing crops. What visually appears as nitrogen deficiency in alfalfa may in fact be inadequate supply of molybdenum.
While creating your plant tissue sampling plan, keep these points in mind:
“Shipping and handling is critical. When samples are shipped wet and in plastic bags, we end up with moldy tissue. We can’t test moldy samples and growers end up having to go back out to the fields and resample,” notes Friedericks. “For best results, use a paper bag and ship dry samples. We hate having to call clients to tell them their samples have to be tossed.”