Plant analysis is an excellent "quality control" tool for wheat growers interested in high yield wheat management, and one that most growers can take advantage of yet this year, according to a Kansas State University agronomist.
The best way to use this tool depends on what the grower wants to accomplish, says K-State Research and Extension soil fertility specialist Dave Mengel.
"There are two primary goals of plant analysis," Mengel says. "It can be used as a monitoring tool to ensure nutrient levels are adequate, or as a diagnostic tool to help explain some of the variability in wheat growth that often occurs this time of year."
The successful use of plant analysis to meet either of these goals starts with using proper sampling techniques.
"For monitoring purposes, 40 to 50 flag leaves should be collected at random at the late boot to initial heading stage of growth. Once the plant pollinates and kernel development begins, nutrients start to flow from the stem and leaves to the developing grain," Mengel says. "For this reason, sampling flag leaves for nutrient monitoring purposes is not recommended once the plant begins to shed pollen."
The leaves should be allowed to wilt overnight to remove excess moisture, placed in a paper bag or mailing envelope, and shipped to a lab for analysis. Do not place the leaves in a plastic bag or other tightly sealed container, as they will begin to decompose during transport, and the sample won't be usable, he says.
"Also, growers should be aware that sampling for monitoring purposes when the crop is under stress can give misleading results, and is not advisable," the agronomist added.
The data returned from the lab will be reported as the concentration of nutrient elements, including potentially toxic elements, in the plants. Most labs compare plant nutrient concentrations to published sufficiency ranges.
"A sufficiency range is simply the range of concentrations normally found in healthy, productive plants during surveys," Mengel says. "It can be thought of as the range of values optimum for plant growth. The medical profession uses a similar range of normal values to evaluate blood work."
Plant analysis is also an excellent diagnostic tool to help understand some of the variation seen in the field.
"When using plant analysis to diagnose field problems, producers should take comparison samples from both good or normal areas of the field, and problem spots. Collecting soil samples from the same good and bad areas is also a good idea," he says.
Mengel says growers should not wait until the boot stage to take diagnostic samples: "Early in the season (prior to stem elongation), growers should collect whole plants from 20 to 30 different places in their sampling area. Later in the season, producers should take the uppermost, fully developed leaves -- those with leaf collars visible. Handle the samples the same as those for monitoring."
"Plant analysis is an excellent tool to monitor the effectiveness of your fertilizer and lime program, and a very effective diagnostic tool. Producers should consider adding this to their toolbox," the agronomist says.