Agronomic advances, biotechnology, and breeding have propelled corn yields to much higher levels compared to just a few decades ago. Fertility practices developed a few decades ago, however, may not be sufficient enough to keep up with today’s hybrids that contain transgenic insect protection and also higher populations.

Back in 2010, the University of Illinois did a trial on nutrient removal of root-worm resistant varieties compared to those varieties’ conventional counter-parts. The results of those trials showed a 14 to27 percent increase of N, P, K, S, and Zn removal per acre with the root-worm resistant varieties. The yields were higher in these root-worm resistant varieties, so we expect more nutrient removal; but the nutrient concentrations in the grain were also higher. With a larger root mass, these varieties are able to explore a larger volume of soil to absorb nutrients.

Earlier this year, DuPont- Pioneer published a study that they conducted across 12 Corn Belt states. Comprised of more than 22,000 soil samples, their study showed that P and K were deficient in a significant number of fields tested, demonstrating that growers may be leaving profit potential in the field.

As we think about plant food nutrients for growing corn, nitrogen management often takes precedence in your soil fertility program, but are you getting the full benefit of your nitrogen dollars? Are there other nutrient levels in your fields that are limiting the full benefit of your nitrogen program?

If you are unsure of the answer to that second question, fall is a great time to collect soil samples to check out your soil fertility levels. If you need some soil testing done this fall, please contact your WS Ag Center agronomist to get this lined up for you.
Hope you all have a safe and bountiful harvest!!

Thank you, Dan Langkamp

N, P, and K always garner a lot of attention when we talk about soil fertility but as many of you know, sulfur has been going into more and more of our fertilizer blends. In the past, sulfur deficiency was uncommon in the Midwest, so what has changed in the last forty years? Although there are several reasons for the increase in sulfur fertilization, three of the main culprits are cleaner air, more accurate fertilizer production, and higher crop yields. Burning fossil fuels released sulfur dioxide into the atmosphere and subsequent rain events would bring the sulfur back to the soil so there was always an adequate supply for crop production. The Clean Air Act was passed in 1970 and was successful at reducing the amount of air pollution including sulfur dioxide. Many older fertilizer blends contained impurities like sulfur which also added to soil levels. Today, commercial fertilizers like MAP and DAP contain much lower amounts of sulfur impurities. Lastly, the trend of increasing yields from our major agronomic crops has created more demand for added sulfur to maintain and elevate our current yield levels.

There are a few things to know about sulfur to make sure you are maximizing your fertilizer dollars. The form of sulfur is important. Sulfur contained in the soil organic matter is not available to plants but a portion of the organic matter mineralizes every year converting the organic sulfur into sulfate sulfur, the form available for plant uptake. Each percent of soil organic matter will release 2-3 pounds per acre of available sulfur annually. Sulfur needs to be managed for the entire season. Corn will take up half of its sulfur after tassel and soybeans will take up more than half of its sulfur need after flowering. According to the Mosaic Company on a per acre basis, a 200 bushel corn crop will take up 30 pounds of sulfur and a 70 bushel soybean crop will take up 25 pounds of sulfur. Fertilizing with sulfate sulfur will get sulfur to the plants right away but sulfate does have the potential to leach from the root zone though not as readily as nitrate. A product like elemental sulfur is not immediately plant available. Elemental sulfur needs to be oxidized by the soil microbes so it acts as slow release sulfur. Another thought to keep in mind is forage crops like alfalfa and corn silage will have a higher demand for sulfur because we are harvesting a larger portion of the plant. A 10 ton alfalfa harvest for the year will take up 54 pounds of sulfur. The form and analysis of sulfur fertilizers varies between products. Dry fertilizers that are commonly used are ammonium sulfate, elemental sulfur, and calcium sulfate (gypsum). Ammonium thiosulfate is a common liquid sulfur source used in this area. Don’t forget that certain products will supply other essential nutrients besides sulfur. Contact your agronomist at WS Ag to determine the best way to add sulfur to your fertility program or for ideas on how to improve your current system.

Thank you, Mark Kendall

In order to help maximum yield potential, it’s important to understand how phosphorus (P) and potassium (K) are utilized in corn and soybean production. Skipping or limiting P and K applications can decrease stress tolerance and consequently reduce yield potential.

Phosphorus is a nutrient required in relatively large amounts by plants. It has a relatively short range of movement in the soil and is considered an immobile nutrient. Plants need P for growth throughout their life cycle, especially during early stages of growth. The primary role of P is to store and transfer energy that is produced through the photosynthesis process to be used during growth and reproduction. The effects of P can increase water efficiency, promote early maturity and improve stress mitigation which all can lead to increased yields. Corn plants increase P uptake rapidly after V6 growth stage and can continue until near maturity. While soybeans demand for P is greatest during pod and seed development where more than 60% of P ends up in the seeds and pods.

Potassium is generally found in the soil in large amounts, but is not readily available for plant uptake to aid in growth and development. Potassium is associated with movement of water nutrients and carbohydrates within the plant. These functions stimulate early growth, increase protein production, improve the efficiency of water use and enhance resistance to diseases and insects. Adequate K levels are important to maximize soybean yield potential. Peak usage of K occurs from flowering through early pod development. A shortage of K at this time can result in yield loss without obvious foliar symptoms.

Also the severity of stalk rot in corn can be minimized with an optimum balance between K and N levels in plant tissue. Potassium has been associated with improvement of stalk strength. When corn plants take up sufficient K stalk dry is moderated after maturity and the risk of lodging can significantly be reduced. In corn K uptake increases rapidly after about the V6 growth stage. When deficiency symptoms become visible K demand is large and supplies are low. Understanding both crop nutrient uptake and removal can help match plant nutrient needs for a targeted yield goal. For corn each bushel harvested per acre removes .45 lbs P and .3 lbs K, in a silage situation K removal is much higher at an additional 8 lbs for every ton silage harvested. For soybeans crop removal varies around .85 lbs of P and 1.45 lbs of K are needed for every bushel harvested.

Although margins are tight in farming right now a sound fertility program is needed to ensure high yield environments in the future.

Thank you, Tom Arndt