The True WHY behind the Corn on Corn Yield Conundrum
Producing extremely successful corn after corn in 2020 has proven to be difficult, as it was in 2010, 2011, 2012, 2015, and 2019. What do all of these years have in common? Significant stresses for long periods of time throughout the growing season. Note that stresses above is plural, signifying more than one.
Corn is a determinate crop. Our highest yield potential is the day that we plant our corn seeds in the spring. From there, we are simply trying to preserve as much of the yield potential as possible. Once we lose bushels in a corn crop, it makes zero difference what we do to supplement/rescue—it’s gone forever. Nothing we do in season actually provides a “yield bump”. This is the reason that we typically only achieve 20-25% of the true genetic yield potential of corn(genetic potential is 1100 bpa). Some believe the actual genetic potential is more like 3000+ bpa, and this I do believe to be true—we’ll save this for another blog post and/or webinar.
This year, and especially recently since harvest has began, the list of the reasons of WHY corn on corn yields have been overall disappointing include(from agronomists, seedsmen, and growers):
- Increased Corn Rootworm(CRW) pressure—including the use of Smartstax, Qrome, and insecticides
- Nitrogen issues
- Soil type
- Corn on corn allelopathy/toxicity
- Very uneven emergence
- High Nitrates
Often times as an industry, we think the use of starter fertilizers, weed and feeds, and strip applying our N will fix the problem. If this was the case, why haven’t these practices bridged this gap between corn/beans vs corn/corn? Because while these may (no guarantee) actually help, they don’t address the root cause of the problem.
Can’t I Just Apply More N?
I will 100% agree that all of the factors listed can contribute to yield loss in corn. But here’s the problem, you can experience the same exact issues in corn after beans (exception is #6—allelopathy). You cannot simply address one or two and fix this corn on corn problem.
Here’s where understanding the true WHY becomes critical. It addresses the root cause, so we can understand the system better and make more informed decisions to allow us to overcome these problems so we don’t continue to experience poor yields/poor income and blame what might be the easiest or what we “think” might be true. Addressing and understanding root causes must involve basing decisions on factual science. It also allows us to implement solutions that can actually fix the problem and not just put duct tape, baling wire, and band aids on it.
So WHY are corn yields year-in-year-out higher, in a bean/corn rotation?
Because soybeans and all legume plants produce very acidic exudates(root exudates) that free tightly bound Calcium and Phosphorus—2 of the most important minerals for photosynthesis, growth, and energy. Ca and P have a very strong affinity for each other. It’s also why in today’s conventional ag mgmt. that 90% of applied Phos is tied up in the soil within 30 days or less and so much money is wasted on Phos fertilizers annually. If one were to do proper sap testing in corn/soybean fields each year(as we have since 2013), this would be easier to grasp. What you’ll find is that in corn, the most common yield limiting minerals are Ca, B, and Mo. In soybeans you will see, much more sufficient levels of Ca. Why? Because of these very acidic exudates breaking this Ca/Phos bond.
How do we fix this, ie the “Solution”?
- Fix Calcium 1st. Also keep in mind that for Calcium to work properly in the plant it needs ample Boron(B). —Gypsum, Calibrate G2, and B4 are great products to assist with this.
- Calcium must be functional in your soil. Soil test levels are very poor indicators of the functionality/ availability of minerals, especially Calcium. Question this? Try some Sap testing and you’ll see.
- Read or reread the Calcium Special Issue Newsletter published back in March 2020.
- Implement a true systems approach. This is far more than applying NPKS and also thinking applied = available. A Systems Approach involves synergies, minimizing antagonisms and considering every single factor.
- Get Mycorrhizal fungi (MycoPlex)working for you in soils. These fungi also produce very acidic organic acids that also break this Ca/P bond. They produce the glue, Glomalin, that creates soil macroaggregates. They build humus. And they hold/create functional Ca in the soil rhizosphere, and improve water holding capacity of soils. Without these fungi being present and active in your soils, Ca will never be functional.
- Manage nitrates in your plants with Moly(hint—Mo2). High nitrates are what signal pathogens/insects you have sick plants and are susceptible to infection. High NO3 also will suppress the uptake of K, Ca, B, P, S, Cl in this order—regardless of what you apply.
- Include legumes as part of your mix in your cover crop plan.