Treating Sunflower With Micronutrients - Do You Benefit?
Mr. Sunflower Grower, could you reap yield and profit dividends by applying micronutrient treatments to your sunflower fields?
The answer is as follows: yes, no, maybe so.
In other words, the value of micro-nutrients for sunflower is one of those subjects on which there never has been, currently is not — and probably never will be — universal agreement. Some growers believe they have reaped a definite yield advantage from micronutrient treatments; others have come to the opposite conclusion. Among university specialists, the reaction presently ranges from a tentative “perhaps” to a definite “no.” Meanwhile, for at least one company which has put considerable effort over the past few years into testing micronutrient packages on sunflower, the viewpoint is quite positive.
TJ Fertilizer of Buffalo, S.D., is that company. Headed by Tom Johnson, the firm markets the TJ Micro Mix™, a “homogeneous package” of dry granular fertilizer that contains a combination of secondary nutrients and micronutrients. The product can be banded alone at planting, blended with NPK and applied as a starter fertilizer, or blended with NPK and broadcast. Included in the standard package are the micros boron, zinc, copper, iron and manganese and the secondaries calcium, magnesium and sulfur.
For sunflower specifically, TJ Fertilizer currently recommends an application rate of one pound per hundredweight of yield goal, with a minimum of 12 pounds and maximum of 20 pounds per acre. Product costs typically run in the neighborhood of $5 to $7 per acre within that rate range. The company does recommend a soil test be used as a basis for determining the need for its product and/or other fertilizer ingredients.
Over the past few years, Johnson has worked directly with several Dakota grower-cooperators and also with the North Dakota State University research/extension centers at Minot and Carrington to develop comparison data.
In the grower-cooperator sunflower trials, “the biggest differences have been in the 400- to 500-pound per-acre range,” Johnson states. “That’s the upper end of the spectrum. What I feel has been a more-typical return (i.e., the yield advantage of Micro Mix versus the untreated checks) would be in the 200- to 240-pound range.”
Replicated trials with oil-type sunflower at the Minot and Carrington research stations in 1997 did not indicate a statistical yield advantage for the majority of micronutrient treatments (see details below). The trials were run in cooperation with NDSU researchers Mark Zarnstorff (Minot) and Blaine Schatz (Carrington).
The Minot and Carrington plots received sufficient nitrogen, phosphorus and potassium for a yield goal of 2,500 pounds per acre. The following treatments were then compared:
• An untreated check, i.e., no added secondary or micronutrients.
• #1 — A micronutrient mix consisting of calcium, magnesium, sulfur, boron, copper, iron, manganese and zinc.
• #2 — A mix with the same group of micronutrients but a higher concentration of boron.
• #3 — A mix with the same micro-nutrients, but a higher concentration of both boron and zinc.
• #4 — A mix with the same micro-nutrient mix as in #1, but with a different carrier material.
The amount of micronutrient mix applied to each plot (treatments #1 through #4) was equivalent to 20 pounds of product per acre.
The micronutrient mixtures had no significant influence on plant height, harvest moisture, 1,000 seed weight, oil content or test weight at either location. In terms of seed yield, treatment #2 (extra boron) showed a statistically significant 268-pound advantage over the check treatment at Minot, while the other three micro treatments were actually lower than the check. At Carrington, all four micro treatments yielded higher than the check. Though the differences were not statistically significant, “the trend was for higher yields with the application of the micronutrients — especially where there was greater boron or boron and zinc,” according to the research report.
“The research we’ve conducted is clearly in its early stages,” Schatz remarks, adding that the Minot and Carrington micronutrient work will continue in 1998. “It still leaves us with a lot of questions; but it’s definitely worth our time to try to develop a larger research base.”
Both Schatz and Zarnstorff point out that many sunflower producers still do not soil test their upcoming sunflower ground to ensure the availability of adequate N, P or K. Sunflower’s reputation as a scavenger of nutrients left unused by preceding crops is an accurate one, they note — assuming such nutrients are indeed present. However, only a soil test can verify the degree of nutrient availability, they emphasize.
Schatz also stresses that the more times sunflower has been rotated onto a given field, the riskier it is for a grower to automatically assume there are sufficient leftover nutrients in the deep soil profile.
Dave Franzen does not see much value in the application of micronutrients for most growers across his state. The NDSU extension soils specialist says he’s aware of very few instances of micronutrient deficiency in North Dakota, and that NDSU research in the ’70s and early ’80s showed little if any response to the addition of specific micronutrients (e.g., zinc, boron) on sunflower.
For the producer who believes he may have fields deficient in one or more micronutrients, Franzen says it’s important to first determine whether that is indeed the case. “And you can do that only through a combination of soil testing and plant analysis,” he emphasizes. “Hardly anyone does that [in North Dakota]; but that’s the way to find out: a combination — not just one or the other.”
Comparing a suspect area of a field to a visibly healthy one would be helpful, too, Franzen suggests. “If you have an area you think might be suffering from some ‘hidden hunger’ or expressing some kind of deficiency, you need to take samples from that area and also from an area that appears to be very healthy — and then compare the two,” he states.
Franzen is not a fan of micronutrient “packages,” either. “If there’s adequate boron in the soil, the difference between ‘enough boron’ and ‘too much boron’ is very close,” he illustrates. “A person may get himself into a toxic situation if he’s not careful. The same is true for a few other micronutrients (e.g., copper).
“If a plant does happen to be borderline deficient in one nutrient and you go ahead and put on a whole package of nutrients, some of the nutrients [will be] competitive with each other for sites within the plant and in the soil,” Franzen ventures. “Iron and manganese are two examples. If you have a plant that’s deficient in iron and you put on manganese, you will intensify the expression of iron deficiency; and if you have a plant that’s manganese deficient and you put on iron, you intensify the manganese deficiency.”
For those growers who do want to experiment with micronutrient treatments on their sunflower ground, the NDSU soils specialist suggests comparing multiple treated and untreated strips on a portion of the field. “Unless they’re doing replicated trials under controlled conditions, a person really can’t have much confidence in the differences they observe,” he concludes.
Not surprisingly, Tom Johnson brings a somewhat different perspective to the issue of micronutrient packages’ value. “The reason for putting those combinations together is that as we do our plot work, we look for a combination of micros and secondaries that consistently gives us a yield response — even when the soil test indicates we should have no deficiency of a particular micronutrient,” he says.
“In our plot work, we’re looking for a tool where we can put a micronutrient package in with our starter fertilizer — and utilize that as a means to increase our total return on our fertility dollar. When we use a combination and then add that additional level of whatever might be deficient, we tend to get significantly higher returns per input dollar,” according to Johnson.
Regardless of where they stand along the often-controversial micronutrient spectrum, however, Johnson, Franzen, Schatz and Zarnstorff do agree on one thing: There still are plenty of sunflower producers who could be — and should be — paying more attention to the availability of adequate macronutrients — N, P and
K — for optimum sunflower production.
“We still need to emphasize proper fertility of the major nutrients — especially nitrogen and phosphorus,” Zarnstorff says. Adds Franzen: “Sunflower will pull out nitrogen from deep depths; but you have to make sure the nitrogen is there before you count on it.” The only way to know rather than guess, the university specialists remind producers, is to soil test.
“We do end up with some resistance [regarding growers] putting fertility on their sunflower,” Tom Johnson agrees. “But that’s why we do our plot work. And that’s why we try to put together the information in various locations and give growers some sense of what the value is of using a fertility input.” — Don Lilleboe
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