Recommendations for plant analysis for wheat
Wheat producers may want to start planning soon for taking tissue samples of wheat for plant analysis. Sampling can be done at tillering-jointing stage, or later in the season near the boot stage. If sampling is done early, this can allow time for corrective measures to be taken.
There are two primary ways plant analysis can be used: as a routine monitoring tool to ensure nutrient levels are adequate, and as a diagnostic tool to help explain some of the variability in wheat growth we see in fields this time of year. Keep in mind, however, that any plant stress (drought, heat, frost, etc.) can have a serious impact on nutrient uptake and plant tissue nutrient concentrations. Sampling under stress conditions for monitoring purposes can give misleading results, and is not advisable.
Sampling at tillering-jointing for routine monitoring
For monitoring purposes, 40-50 whole plants, without roots, should be collected at random from the field. The plants 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 plants in a plastic bag or other tightly sealed container, as they will begin to rot and decompose during transport, and the sample won’t be usable.
The data returned from the lab will be reported as the concentration of nutrient elements, or potentially toxic elements in the plants. Most labs/agronomists 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. 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.
The sufficiency ranges change with plant age (generally being higher in young plants), vary between plant parts, and can differ between varieties. So a value slightly below the sufficiency range does not always mean the plant is deficient in that nutrient, but it is just an indication that the nutrient is relatively low. However, if that nutrient is significantly below the sufficiency range, then one should ask some serious questions about the availability and supply of that nutrient.
Levels above sufficiency can also indicate problems. High values might indicate over fertilization and luxury consumption. Plants will also sometimes try to compensate for a shortage of one nutrient by loading up on another. This occurs at times with nutrients such as iron, zinc, and manganese. In some situations very high levels of a required nutrient can lead to toxicity. Manganese is an example of an essential nutrient which can be toxic when present in excess.