Today's higher-yielding corn hybrids, having larger root systems, extract larger levels of soil nutrients - particularly phosphorus and zinc. That comes with production and efficiency benefits but requires greater consideration for micronutrients, even if fields, historically, have never shown a micronutrient deficiency. And while most growers and retailers are aware of the needs for zinc and boron, regional trends noted by soil test labs suggest micronutrient levels are being neglected.
Statistically, more than half of all fields need more micronutrient fertilizer applications
Specific to Minnesota, North Dakota and South Dakota, AgVise Laboratories reports more than 80 percent of fall 2014 soil samples in some of the soil test lab's regions had zinc levels at less than 1.0 ppm.
In a five-state area, 50 percent of the soil samples analyzed by A&L Great Lakes Laboratories of Fort Wayne, Ind., were rated low in zinc and 73 percent rated low to very low in boron.
Growers are always conscious of soil health. But when commodity prices are lower, growers tend to cut back on inputs. To keep their costs down, most invest in NPK and leave out the micronutrients.
Gary Tuxhorn, Ph.D., principal scientist at United Suppliers, advises against cutting back on inputs that have a good ROI: "Growers have been pulling good yields from their soil for the last several years. Unless they are adding the nutrients back in and maintaining a good fertilizer balance, they are mining the soil of micronutrients. Continue to do that, and we will start to see an impact on yields."
In their Nutra-Links tissue sampling program this year, United Suppliers found about 48 percent of samples to be deficient in zinc, about 72 percent deficient in boron and 51 percent of the samples showed some magnesium deficiency. While there is some potential field selection bias in how representative these samples are of all acres (producers participating in the Nutra-Links program likely suspect a deficiency), there were a large number of acres sampled.
4 Tips to ensure micronutrient deficiencies are not limiting yields
1. Request micronutrient levels for all soil and tissue test samples - as part of the 4R Nutrient Stewardship Principles - to develop the right nutrient management plan.
2. Apply (at least) maintenance rates to soils having moderate micronutrient levels to avoid deficiencies.
3. Factor the greater nutrient uptake levels associated with today's higher-yielding crops when determining application rates.
4. Look for innovative micronutrient fertilizers, such as Wolf Trax DDP Nutrients, for guaranteed plant availability and better uptake.