Now that crops are planted and (hopefully!) off to a great start, it's time to start thinking about what in-season management decisions are going to be done this year. There are plenty of considerations to take into account:
How is the crop looking today?
What are these crazy markets going to do next?
What weather is coming in the next couple of weeks to months?
What will my disease pressure look like later this year?
All that being said, when it comes to decision-making, we need to make the best decision we can with the information we have today. That’s why tissue testing can be so valuable – it gives you up-to-date information on what's actually going on in your plants.
What is a tissue test?
Tissue tests involve taking tissue from the plants you have growing in the field and sending it to a lab for an analysis of nutrient levels. The analysis will show you what the nutrient levels are on the day the sample was taken. The report will vary depending on your lab, but generally they let you know what nutrients are low or deficient based on the plant’s growth stage when you took the sample. This will help you understand what is going on inside the plant and can often pinpoint deficiencies before they show themselves.
How do I take a tissue sample?
First, determine what crop you want to sample to find the optimum sampling time. Corn is usually sampled anytime from V4-V12. Because the plant is still primarily living off the seed’s energy before V4, waiting until V4 or later will give you a more accurate reading of what's actually going on in the plant. It’s recommended that you then pull another sample from brown silk to R4. Often we want to get the first samples done early for an opportunity to combine a micronutrient application with another planned pass (like an early fungicide application pass), while the later samples tell us where we ended up or (as we like to call it) those are our “report card” samples.
For soybeans the first sample should be taken from V3-V5, then followed up in early reproductive stages.
Next, it’s time to gather the sample. To properly gather a corn tissue sample, you need to grab the uppermost collared leaf. You’ll want to be sure to only pull the collared leaf from each plant, and grab enough tissue to make a softball sized collection. Randomize the sample (around 30 plants) across the field; having samples that represent about 40 acres is a good rule of thumb. For soybean tissue tests, you’ll want to grab the uppermost developed trifoliate from around 30 plants or enough to make a softball sized collection. Avoid older plant tissue and trifoliates that have not completely opened, as well as the petioles, in your sampling bag.
Finally, let's send the tissue test. Use a paper bag that can let the tissue breathe and that is small enough you’re able to keep it cool. If you can’t mail the samples out until the next day, you may want to put the samples in the fridge – but avoid freezing and avoid leaving them in a hot truck for an extended period. Next, sample tissue early in the week. Tissue sampling on Thursdays and Fridays could result in your sample sitting in a hot delivery truck – decomposing – over the weekend. If you don’t live close enough to hand-deliver the samples, it is best to pull the samples between Monday and Wednesday. Next, make sure the plant tissue is not excessively dirty; if they are, try to remove the dirt before putting the sample in the bag. Finally, ship the tissue samples off to the lab as soon as you can! Not only will that reduce spoilage, it should also get you your results faster in order to make timely management decisions.
It’s always best to make in-season decisions based on in-season data. Tissue tests are a great way to get solid data in your hands early. If your samples come back adequate for the growth stage your plants are at – congratulations, that’s great news! If not, be glad you caught it early. Do what you can to make in-season adjustments and know future varied testing might be necessary to address any concerns that cannot be adjusted in-season. Also, make sure your macros are in order before trying to address micros to get the most out of your application.
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