Look up “Boron deficiency” online right now.
Depending on the source, it is either the #1 or #2 most deficient nutrient in crop production IN THE WORLD!!!
The odds that your soils – and ultimately, your crops – need more boron is pretty high. Boron is important for moving sugar, food, and hormones inside plants all through the year. It is also important for cell structure. Calcium puts the starch in the leaf, but boron moves it from the leaf to the ear.
Adequate levels of boron reduce missing seeds by moving seed growth hormones. For example, if your corn ear doesn’t fill out all the way to the end, it may be short on boron. The challenge is boron leaches, so it’s tough to build levels in your soil, especially in light, sandy fields where annual rainfall or irrigation volumes are high.
Determining Your Need For Boron
The best way to determine your soil boron levels is to do a complete soil analysis. Unfortunately, many of the soil tests we see on a daily basis don’t even have micronutrients on them. As you send in your samples, be sure to get a complete analysis including N, P, K, calcium, sulfur, magnesium, sodium, zinc, boron, copper, manganese, iron, and any other nutrients you would like to see. Base saturation, organic matter, soluble salts, excess lime, and soil pH are important, too. We are using the SC3M test at Midwest Labs to analyze the soils from our farm.
Target Soil Test Values
In heavy soils with good levels of organic matter west of the Mississippi River where annual rainfall is lower, we’ve seen good success building boron levels in the soil. On our farm, we have built boron above the minimum threshold of 1 part per million (ppm). We have many acres now above 2 ppm, and we’re finally seeing adequate to above average levels consistently on our plant tissue analysis throughout the season. In order to safely do that, though, soil calcium levels must be good, too. We’ve found a 1000:1 ratio of Ca:B to be a good target, but that number may be different for your soils.
Application Timing, Rate, and Product Choice
Where we farm, soils are frozen for nearly half the year and rainfall is typically low. This allows us to do fall applications without fear of losing boron to leaching. We’ve been building levels of boron in our soil with broadcast applications of a dry 15% boron product. This year, that costs $0.71 per pound or $4.73 per pound of actual boron. Compare that to $14 per gallon for a 10% boron liquid product, and you can see why we like the dry formulation when it comes to building soil test levels. The fear most farmers and even fertilizer salespeople have using boron is applying too much at one time and hurting the crop. We’ve safely spread several pounds at a time without issue, but again – we have heavy soils and plenty of calcium to safen it. Also, broadcasting is safer than banding if you are worried about boron toxicity, and broadcast is the method we use when building soil boron levels.
If you foliar feed boron in-season, that’s where the liquid obviously fits better than the dry product. If you foliar feed, it will show up in your tissue tests for up to a couple of weeks. Then, your levels will likely go down again. Fertilizing the soil rather than the leaf tissue has been better for us, and depending on your soil, it could be for you too. If you do go the foliar route, targeting just ahead of the reproductive stages has been good timing. I’d suggest tissue testing each week through the growing season to see how your program is doing and to help you determine the best times to foliar feed on your farm.