February 21, 2018
Tissue samples and soil tests have been used for years as a way to get a good look in-season at the amount of fuel in the “fuel tank,” measuring nutrients in the plant and the amount available to the plant in the soil.
This year, Mark Herz, WinField United agronomist based in Nebraska, notes growers who tissue-tested in 2017 were better prepared to respond to nutrient demands in-season.
Based on tissue samples submitted to WinField United, corn across the state was less likely to be deficient in nitrogen, sulfur, magnesium and manganese in 2017, although a greater percentage of samples were deficient in zinc or potassium compared to 2016.
“Weather, crops and soils are ever-changing. So we’ve got to be able to react to that, be able to call those in-season audibles,” Herz says. “That can be intimidating. But what I’ve noticed lately, over the last few years as we head into 2018, producers are using more critical thinking.”
This includes timing and rates for different fertilizer applications, and that’s where tissue testing has played a role, Herz says — and not just for major nutrients like nitrogen, but also micros like sulfur, boron, manganese and magnesium.
However, tissue tests can also help identify trends in nutrient deficiencies. And Herz offers a few things to keep in mind for those setting the foundation for the 2018 growing season:
• Don’t be quick to dismiss. “Sometimes you go out and pull a tissue sample, and it may not give you the results you were hoping for or expecting,” he says. “Don’t just dismiss it. You’ve got to investigate why.”
Nitrogen is one example. “From year to year, the amount of nitrogen available to the plant can swing based on environmental conditions, even though the amount you applied is the same,” he adds. “Sometimes people pull a sample that shows you’re a little bit deficient on N, and the response is, ‘It can’t be; I put on X amount.’ Yeah, you did, but the weather or the temperature threw you a curveball, so you’ve got to make some adjustments and use that as a learning experience. If you’re done fertilizing, you can still use that information as you plan for the next year.”
• Adjust for yield. On higher-yielding fields, Herz says nitrogen needs may be higher than expected. Depending on the season and mineralization in the soil, nitrogen needs will differ regardless of how much was applied up front.
“On some of this ground, we’ve taken a lot of bushels off over the many years it’s been farmed. In some cases, we’re driving on a gas tank gauge that’s running pretty low. I’m not saying we need to go out and apply a bunch of fertilizer, but you’ve got to understand where you’re at to give that crop the best chance to produce the results you’re expecting,” he says. “Your yield goal could be 200. And if you’re getting into the season and things are looking a little bit better, [and] you’re increasing your yield goal to 220, I’d certainly take a look at that point at increasing nitrogen and sulfur.”
• Nutrient demands are changing. Yields are continually increasing in modern hybrids, but with these changes in hybrids comes a change in nitrogen demands throughout plant growth stages, Herz says. This is another reason tissue tests play a role for making in-season adjustments.
“The difference with modern hybrids is not so much leading up to tassel, but it’s what happens to nutrient demands after tassel,” he says. “So the calendar gets pushed back a little bit, and the nutrient demand filling that grain is still there, and it’s there until black layer. If we’re applying timing strategies that we used 10 years ago, that’s not the best with today’s hybrids, we’ve got to match a little better placing that nutrient closer to when the plant’s going to need it.”
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