Now that our corn is in the ground, it’s time to focus on the management and nutrition of our crop. Often times, when we consider what nutrients our corn needs between the V4 and V8 time frame, we think of nitrogen (N). Another nutrient that is essential to corn production, but is often forgotten or taken for granted is sulfur (S). When it comes to nutrition, a corn plant’s S needs rank only behind N, phosphorous (P), and potassium (K).
S is critical to ensuring balanced nutrition in our corn crop. In the plant, S helps ensure that the plants efficiently convert N into protein. While supplying an adequate amount of N alone is good, supplying it with an ample supply of S along with that N is essential for a high-performing, efficient crop that produces maximum yields. When I think about S in corn, I compare it to maintaining a balanced diet. Our bodies can function well if we consume only two to three of the four major food groups. However, we perform much better if we keep a good blend of meat, fruit and vegetables, dairy, and bread in our diet. A corn plant is no different.
Many of you may be thinking, “I’ve never applied S in the past and I’ve raised good corn, so why do I need to now?” In the past, S fertility hasn’t been a major concern due to the fact that we received “free” S from several sources such as atmospheric deposition, manure sources, and mineralization of soil organic matter. However, as we’ve improved air quality, we now have less acres receiving manure applications and have simultaneously increased our corn yields. This has resulted in S deficiencies when it’s not supplemented in a fertility program.
To date, we still receive a little S from the atmosphere and some by way of organic matter breakdown or mineralization. Determining how much S that corn extracts from the atmosphere and the rate of mineralization is very difficult and can vary significantly due to weather, soil temperature, and soil moisture. Quantifying S levels in our soil can also be challenging due to the accuracy of measuring very small quantities. Also, since sulfate S is highly mobile, a soil test value is only accurate for the specific time in which the sample was pulled. One method to determine your need for S is through tissue testing. A leaf tissue analysis pulled in close proximity to the time in which you intend to make a potential S application is the best method to accurately determine your overall S level and need.
A corn plant requires 0.1 to 0.12 pound of S per bushel. Corn takes up S in the sulfate form, which is highly mobile in the soil and subject to loss due to leaching. Due to this potential for leaching and loss, it’s important to apply fertilizers containing the sulfate form of S as close to the point of plant uptake as possible. As you can see in the images below, S uptake aligns similarly to that of N. Its similarity to N, and because of the potential for leaching, means that applying your S in conjunction with N between the V4 to V8 growth stage is a very good practice to feed your corn when it needs it most.
Because S is considered a secondary macronutrient, it is required in smaller quantities than N, P, and K. However, this does not make it any less important, as it is still one of the 16 essential nutrients to production, and is critical to overall crop yield and development.
For more Agronomic News from Luke Schulte, please visit his Agronomy Page.