By Brian Hefty

Cut, cut, cut… Many farmers I talk to this year are trying to cut “extra expenses”.  Here’s the problem.  What’s an “extra expense” and what’s a good investment?  The worst thing you can do is cut $20 in “expenses” and lose $40 in yield.  While you can shave 25 or 50 cents an acre here and there, those things don’t add up as quickly as making wholesale changes to your fertilizer program, where saving $20 per acre may be possible.

Whether you cut your fertilizer rates this year or not, we encourage you to use plant tissue analysis throughout the growing season to better identify your strengths and weaknesses, as well as your overspending and underspending with your fertility program.  Here are my top 6 tips when it comes to using plant tissue analysis to improve your fertility program.

  1. The most important thing you need to know is that plant tissue analysis, in my opinion, is almost worthless unless you sample on a weekly basis.  When you send in plant leaves to be analyzed, the lab can only tell you the level of nutrients in that plant THAT DAY.  They can’t tell you what the nutrient levels were last week or what they will be next week.  We suggest pulling samples for 8 to 12 weeks in the same spot so you can track the progress.  Yes, one week you may have good levels, but when you have poor levels for 3 weeks, for example, something needs to be addressed.
  2. Use tissue analysis to diagnose visual field problems.  For example, yellow tops in corn happen almost every year in fields in our area.  Pull leaves off yellow plants and send them in to find out what the real problem is.  I have sampled where I was convinced the issue was sulfur, but upon sending in tissue samples the results showed the sulfur was fine; zinc was the culprit.  Other nutrients that could lead to yellow tops include manganese and copper.  It’s hard to fix a problem if you don’t know what the problem actually is.
  3. Pull enough leaves and the right leaves.  Send your samples in a paper bag, not plastic.  Tissue sampling is super simple and easy.  Anyone can do it.  There are just a few guidelines, depending on the crop you are sampling.  For example, don’t send in dirty leaves.  If there is dirt on your leaves, that will elevate your iron numbers.  To fix that issue, simply wash your leaves with distilled water when necessary.  You shouldn’t have to do this often, but if for some reason you have a bunch of dirt on the leaves, you’ve got to get them cleaned.  Our advice is to go to this page and take one minute to read the sampling information for your crop.
  4. Pick the same spot in the field, the same day of the week, and the same time of day every time you pull tissue samples.  The idea here is you want to keep as much consistency as possible in everything you do.  Then the trends you see with your fertility levels will mean more because they are more real.  Also, our advice is to sample every Monday morning.  That means no samples sitting in the post office over the weekend.  It also means you have your results back by Thursday or Friday.
  5. You can use tissue samples to adjust your foliar feeding and sidedress decisions, but the big thing we use it for ourselves is to make changes in next year’s program.  If you sample on Monday and see your results showing boron deficiency on Thursday, for example, you can certainly go out and foliar feed with some boron on Thursday or Friday.  The problem is that once you find out you have any deficiency, you’ve already lost some of your yield potential, regardless of how much later fertilizer you throw at the problem.  Once you sample for 8 to 12 consecutive weeks, you will have a good idea if you have a lot of areas excessive or deficient in certain nutrients.  Those are the things you can adjust with next year’s plan.
  6. Start sampling corn and wheat almost as soon as they get out of the ground.  With broadleaf crops like soybeans, we usually advise waiting a month or so after emergence, then sampling for 8 to 12 weeks.  Broadleaf crops usually bring up more of their nutrients late in the year.  Grass crops typically pull in more nutrients early.

Challenge yourself to get this done this year.  I know you may not have done it before, and who isn’t busy, but ask yourself, “How can I change my fertilizer program if I don’t know if my crops are short or long on nutrients?”  Plant tissue analysis can help you answer that question.