Sulfur deficiency in corn can masquerade as nitrogen deficiency. Boron deficiency in soybeans may remain hidden — the only sign being a yield below optimal.
Liebig’s Law of the Minimum sums up the whole concept of balanced crop nutrition. Similar to staves of a barrel — if one is missing, the barrel won’t hold water — a plant will only do as well as its most limiting nutrient. A plant with a nitrogen deficiency will only do as well as the amount of nitrogen that the plant can take up. The same applies to each essential nutrient: The crop will only do as well as the amount of the nutrient that is there to utilize.
Going down the list, there are the three macronutrients everyone thinks of —nitrogen, phosphorus and potassium (N, P and K) — followed by three secondary nutrients, magnesium, sulfur and calcium. Eight micronutrients round out the list of elements delivered via fertilizer: boron, chlorine, manganese, iron, nickel, copper, zinc and molybdenum. The remaining three essentials — hydrogen, carbon and oxygen — are the inputs delivered by Mother Nature.
A great resource for “digging deep” into nutrients is the “Periodic Table of Crop Nutrients”.
It’s an interactive list: Click on “H,” and “Quick Facts” about hydrogen pop up, for instance. Nearly all organic compounds contain hydrogen, and plants use massive quantities of it; luckily, the plant gets its hydrogen from water.
Once you’ve gotten the Quick Facts on a nutrient, say potassium, you click on another tab, called “Dig Deeper,” and you find a more thorough entry. In this case, you can learn that one of potassium’s most important functions in the plant is that it can activate at least 80 enzymes that regulate the rates of major plant growth reactions. Potassium also influences water-use efficiency.
From there, you can click on a button “to dig even deeper,” or you can open a third tab to look at “Deficiency Photos.”
All 17 nutrients combine to allow the plant to complete its life cycle. The soil test is the first step to rooting out any deficiencies that could hold back your crops. When looking at the world of soil fertility, nitrogen receives the most attention, and is often mistaken for the most important nutrient. As Liebig’s Law explains, it’s no less or more important than the other essential nutrients.
Three nutrients are called “secondary” because they are needed in slightly smaller amounts than the macronutrients, but depending on the crop, the need can range in the tens of pounds per acre.
Sulfur is a secondary nutrient, but is essential in the formation of amino acids. Plants use nitrogen as a backbone for proteins — that is, nitrogen is essential in the formation of amino acids — but three of those amino acids also need sulfur. So in the end, in certain crops, to build that protein up, you actually need to have sulfur available.
Are there any nutrients producers don’t need to worry about? As a general rule, the ancient seas that covered North America left soils loaded with a bounty of calcium. Still, the soil test may show a deficiency in calcium, which can be corrected with a fertilizer. Producers who are adjusting pH with the use of lime are also boosting calcium in the soil. If calcium levels are too high, they can bind magnesium (another secondary nutrient) and create an issue with magnesium availability or uptake.
Imbalances in the soil need to be corrected. Though micronutrients are required in smaller quantities, when they are deficient or missing, they will limit yield. One of the key concerns when adding micronutrients is getting them everywhere they are needed. When using a high-analysis fertilizer, you are applying it at a very low rate to the soil, and you won’t get as good of a distribution as with a low-analysis product.
When comparing a granule fertilizer that has 1 percent zinc to a granule fertilizer that has 35 percent zinc, the latter has less distribution. Applying MicroEssentials®, which has 1 percent zinc, or Aspire®, which has 0.5 percent of boron, gives more granules per acre and a better distribution when applying that nutrient. Focusing on maximizing that root interception with that nutrient or granule maximizes uptake for those small amounts that are being applied.
With a program of soil testing and applying of all the important nutrients, farm producers will reap the benefits.