Soybean School: High Yields Start With Soil Health


Are you paying enough attention to your soil? That’s the first question Iowa crop consultant Michael McNeill asks farmers when they want to talk about how to increase soybean yields.

“Soil health is vital to optimizing profits in any crop we try to grow. Without good soil health we don’t have a chance,” says McNeill. He’s been consulting for 35 years and currently helps manage 165,000 acres of crops.

In this episode of Soybean School, McNeill offers a series of tips to help farmers better understand their soils and optimize profits. For McNeill, soybean success starts with proper soil sampling and that doesn’t include grid sampling.

Iowa agronomist Michael McNeill advises his clients to soil sample by soil type rather than using a grid.
Iowa agronomist Michael McNeill advises his clients to soil sample by soil type rather than using a grid.

“I have found that sampling by soil type or soil management region is the way to go. Grids were developed because they are easy to work with and handy to put into your computer,” says McNeill. He notes that quite often one square in a grid can have pH readings that range from 5.4 to 8.3.

“If you pick some samples out of that, mix them together and send it to the test lab you get a pH of 7, which means the soil is perfect.” But that’s not the case, says McNeill noting that much of the grid likely requires fixing. “Part of it needs remediation, a little more lime, and the other part of it is way too high, it doesn’t need anything.”

McNeill believes farmers are often too fixated on the status of nitrogen, phosphorus and potassium (NPK) in their soils and need to do a better job focusing on micronutrients. “We’ve spent the last 30 or 40 years focused on NPK and it has done a remarkable job of improving yields all over the world, but it has done so at the expense of degrading soil organic matter, degrading soil biological activity and soil aggregation.”

When it comes to micronutrients, McNeill likes to focus on percent Base Saturation.

“We look at mineral tests and Cation Exchange Capacity but percent Base Saturation is extremely important, particularly the calcium, magnesium, potassium ratios. If they are right, our soils will be healthy, mellow and have good gas exchange. We get C02 out of the soil, we get oxygen into the soil, and everything works well.”

Dig into more Soybean School articles and videos here

When managing soybeans, McNeill also insists that his clients be aware of mid-season nutrient levels within the plant. “A lot of times you look at your field and it looks pretty good. It’s green, uniform and beautiful but you have to look for what I call ‘hidden hunger.’ The only way you can do that is to do some chemistry testing.”

McNeill recommends his clients use laboratory Sap Analysis to measure nutrient concentration in the plant to forecast deficiencies that could impact yield. “I use a Sap Analysis to check the sap of the plant. That tells me a lot because some minerals are very mobile in the plant and some are not.”

McNeill tests a bottom leaf and a fully mature top leaf and compares the results. “If I have a lot of calcium in the bottom leaf… and very little in the top leaf, I know we have a calcium deficiency,” he says noting that calcium is a highly immobile nutrient. “We can foliar feed and bring that back into proper alignment.”

Other minerals such as phosphorus and nitrogen move very quickly in the plant and it’s important to ensure that, in the case of N, the same amount of the nutrient is available to the top and bottom of the plant. If that’s not the case, you have a deficiency, he adds.

But ensuring your soil is effectively delivering nutrients to the plant is only part of the soybean yield equation, insists McNeil.

Check out this video for McNeill’s further tips on the importance on proper soil conditions at planting, planting depth, plant spacing, scouting and how to properly apply foliar fungicides.

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Soybean School (view all)Season 5 (2016) Episode 28

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