By: Dan Kaiser
Plant tissue analysis is a singular tool that we have within our toolbox that can be used with other tools to try to help us assess nutrient deficiencies within fields. With studies funded by the Agricultural Fertilizer Research and Education Council (AFREC), we commonly use tissue analysis, not only as a way to assess performance of treatments within the field, but also as a way to collect data to look at evaluating currently used sufficiency guidelines for particular tissue analysis collected at diagnostic growth stages. There are a few things to consider when you're taking plant tissue samples.
First, timing of sampling is critical. We want to avoid sampling too early in the growing season or too late in the growing season. This is because too early in the growing season, plants typically have not taken up a large portion of their nutrients, and too late in the growing season, plants tend to redistribute nutrients within their tissues and tissue concentrations will decline. Second, make sure you're sampling the appropriate plant part for a particular crop species at the appropriate growth stage. Finally, it's important to diversify your sampling, sampling multiple areas within a given field.
If you're looking at comparative sampling, one thing to remember is sampling the good, the bad and the ugly. Sampling three areas of the field if you're looking at trying to identify what may be happening with visual nutrient deficiencies is very important, because this allows us to make a judgment based on comparing the results for individual nutrients within those different areas of the field. Avoid end rows or avoid areas of the field where the plants are dead or dying, because dead or dying plants are likely going to have very low nutrient concentrations and are not going to lead to worthwhile results within your given field.
You're going to be sampling a composite sample, which means you're going to be sampling multiple plants for one sample within a given field. It's also important to know how many samples are recommended for a given crop. Check with your lab to know how many samples they recommend to get an accurate result. Second, it's important to check your samples for soil contamination as you're collecting them. Small plant samples or samples collected from fields that are not fully canopied, rain splashing on the soil surface can leave soil particles on the lower parts of the leaves. Third, it's important to handle your samples properly. Paper bags allow your samples to dry, while plastic bags if left in a hot vehicle will quickly deteriorate your samples to a point at which they're less useful for analysis.
The last thing you want to consider taking to the field is a soil probe, because collecting soil samples along with plant tissue samples can also help you when it comes down to determining what's going on within a particular area of the field.