OK- so you probably get it from the title- This blog has something to do with nutrient availability and the investment we all make when growing crops each season. Specifically, I want to reference the crop nutrition that we spent much of the winter talking about and the early spring carefully applying to each acre. The goal was and remains to scratch out the maximum return per acre for every dollar spent on crop nutrition whether a macronutrient like Nitrogen, Phosphorus or Potassium, a “soon to be macro” nutrient like Sulfur. If you are familiar with the concepts of the “sink” (what drives nutrient uptake) and the "source" (what is available to be taken up), then we can talk about a balance. For nitrogen, that means we want our plants to always get all the N they need, but never have too great of a surplus. If we succeed in this- the crops grow to maximum potential and the environment wins, with little runoff.
So, we talk about nitrogen and nitrogen use efficiency a lot. And we should pay major attention to the nutrient: we spend the most on it, apply it to our fields in the biggest quantities and its impact on yield is the largest of any nutrient. We talk about applying it efficiently. I also hope you had a conversation with your agronomist about PROTECTING that nitrogen investment last fall and/or this spring. It is the management of nitrogen, along with its associated sidekicks- Potassium and Sulfur, that I want to focus on in this blog.
The recent several weeks in much of the eastern South Dakota portion of Wheat Growers territory have been extremely dry. This meant that much of the crop nutrition we placed on or in the ground sat there in relatively dry soils, if it was worked in, or worse yet, sat on the surface of the ground…without rainfall… waiting for the potential rainfall event to come along.
This raises two questions:
1) Have we lost any of the crop nutrition we have applied, and if so, how much remains?, and
2) Will there be any effect on the wheat that is up, the corn crop that is now emerging, or the soybeans we have just planted?
Controllable forms of nitrogen loss. Nitrogen stabilizers are a key management tool.
Let’s start with the source- what we applied, and what we may have unfortunately lost. The source is the sum of all the nitrogen you apply, plus nitrogen released in the N cycle by mineralization minus any lost to volatilization, leaching or fixation into organic matter. Fixation occurs every year, and we have that covered with our management plans. With the dry weather- leaching is not a concern right now, but VOLATILIZATION- that may be the kicker. Older work by NDSU still applies here- untreated urea left on the ground surface is susceptible to volatilization loss- maybe as much as 30-40% loss, in fact, over a period of several weeks. Adding a nitrogen stabilizer- like an NBPT containing product such as Wheat Growers' RemaiN to your urea significantly reduces that loss potential. With three weeks on the ground surface, I would say some of that nitrogen, maybe 10%- maybe a little more- is potentially lost. Many factors play into this, but the losses are real, and will take management in the next several weeks.
As corn gets growing, we must manage it closely, as there may be some early season nitrogen deficiency showing up. This may be from lost nitrogen, but it may be from a couple other sources as well, and we need to understand this complex situation. Let’s jump over and meet the other players in the nitrogen use game and see how dry conditions affect them. Then let’s get back to management.
Meet the other players in nitrogen use: Potassium is a macronutrient that you all know and love- or hate, as it may be. Potassium is an odd duck- hard to predict in the soil. However, it is CRITICAL to nitrogen use in our plants. It is involved in uptake and redistribution of nitrogen in plants like no other nutrient. The rapid uptake of nitrate into a plant is dependent on the presence of potassium in the soil solution. Under dry conditions, even soils with high or very high K tests may be DEFICIENT in AVAILBLE K. Clays are notorious for this- the layers compact under dry conditions and simply do not give up K to the soil solution. Potassium is also involved in moving nutrients like nitrogen around in the plant. Potassium deficiency- real or dry weather induced- exacerbates nitrogen deficiency.
Sulfur is a macronutrient-to-be, is water soluble in the soil (there’s that effect of drought again) and we must pay attention to available sulfur levels. We aren’t getting as much from the rain as we used to. Sulfur is critical, because, like potassium, sulfur affects nitrogen within our plants. Sulfur is critical in ATP transfer, a process that moves nitrogen around in the plant, plus sulfur is a part of a couple critical amino acids.
So- nitrogen management is really CROP NUTRITONAL MANAGEMENT. Yes—have a conversation about nitrogen, but potassium and sulfur are closely tied to N use and efficiency, and need to be in the discussion.
Watch corn crops closely in the next few weeks. For fields where fertilizer sat on the ground surface for a fair amount of time, and for all fields, I strongly suggest having a conversation about TISSUE TESTING, and maybe even early season SOIL NITROGEN testing (nitrate and ammonium nitrogen). We need to know where our crop is at- nutritionally. Topdressing, side dressing or Y-Drop applications of additional crop nutritional products may pay big dividends, if unfortunately, Mother Nature became a thief in the recent weeks, like I suspect she may have.
Visit with your local Wheat Growers Agronomist to talk about crop nutrition management and programing like the Spray On Profits program Wheat Growers. Let’s keep the crop nutrition rolling along in our fields, keep our plants happy and healthy, so we can maximize yield and maximize ROI.