What is your limiting factor? How can we eliminate those limiting factors, and advance to your next goal?
The first step is water management. Water management is crucial to crops and stabilizing yield. However, water alone is only going to get you so far. Add nutrient management to water management, and possibilities abound. This article will discuss nutrient management strategies to help boost the health of your crop and yields, and give you the best return on your investment of money and time.
Nutrient Management
Nutrition management has a very high potential for increased yield, but we are learning that applying nutrients each year for a one and done approach is not the best way to ensure your crop is provided for. For example, this uptake chart gives a good visual on nitrogen need in a corn plant. As you can see, 230-bushel corn requires more than 7 pound of nitrogen per acre per day for 21 days. That is an incredible amount of uptake that happens in a really short window. How do we deliver that? Right now, applying fall anhydrous is the main method. The things we have learned over the past year are really starting to challenge this method. If we could spoon feed this plant, how would that change its growth and yield?
One of the tools we started using is one Netafim developed to help us visualize the numbers. We input the day length of the hybrid, yield goal, nutrients already in the soil and what we are applying with the planter. It takes GDUs of weather and inputs those based on your growing season, and shows us when we need to start applying each nutrient in the profile. This allows us to stay ahead of the plant needs and attempt to provide all nutrients for optimal yield. Sounds pretty simple, right? But the next step is ensuring those nutrients are getting into the plant.
How do we measure to verify the levels are correct in the actual plant? Tissue sampling. We have been tissue sampling on our farm for 15 years or more. It may not provide an exact number, but tells us if we are in the right range. We are always on the lookout for other tools, and are currently experimenting with some SAP sampling as well. However, tissue sampling remains our current best practice due to the amount of data we have, and our knowledge in how to use that data. Over the past year, we have been tissue sampling and graphing those values in relation to time frames and growth stages. While this data may not help us make decisions this week, or next week, it helps us make long term decisions that affect the trajectory of next year.
One of the challenges we ran into when we just focused on tissue sampling is that growers would apply a nutrient, and we wouldn’t see that number move. Why wouldn’t we get a response when we apply a certain nutrient? We decided to step back, and look at the bigger picture. We now do soil and tissue sampling together.
In Depth Soil Sampling
Two years ago we were introduced to the Next Level Ag group out of South Dakota. Their soil sampling program is much more intense than a standard soil sample.
The left side of this graphic is a standard soil sample. The green box is more of a plant available or soil health scores. If you're familiar with the H3A extraction or the soil health, that's what we're looking at. What we've started to learn is that just because we have potassium in the soil and it's showing up over here on the on the standard test, that doesn't mean the plants can get ahold of it. Potassium and calcium are two nutrients that a lot of times are not plant available. We will highlight some of the things that we've learned with that below. A couple other numbers on here are really important and we're starting to look more intensely. One is the HT3 CO2 score. CO2 is emitted from your soil by the biology, and if you measure the CO2 in the soil or coming off the soil, (they actually take your soil sample, put it in a little chamber, and then measure that CO2 coming off of it for 48 hours) it gives you a score for how biologically active your soil is. It shows how fast the engine is running in your soil. If you have dead soil and a low score that soil is not working for you.
This is a really important number to understand. There are a lot of biological companies out there now that you can buy biology in a jug or on a seed treatment. The goal is to get that number higher. It's to get the biology cranking in your soil faster. We are putting a lot more interest in what this biological number is and how much respiration. We're going to be looking at some sensors this year that will lay on the soil in the field and it will monitor your CO2 respiration 24 hours a day. We are excited to have this data. One of the agronomists we work with in Idaho used them last year and they were able to detect and verify CO2 response out of the soil based on products they were applying, either foliar or with irrigation. Some products slowed the respiration down, some products sped the respiration up.
One of the places that we've used this test is in a field with a pivot and drip irrigation in the corner. In 2020 there was higher yielding corn in the corner than underneath the pivot. Being the curious people we are, we wondered why this happened? We collected soil samples underneath the pivot and in the corner. On the standard soil sample, the calcium number was very similar, but when we looked at the plant available calcium, under the pivot was 337, and outside the pivot was 433, a 30-40% different. What we realized was that bicarbonates in water tie up calcium. Irrigation water has essentially neutralized the calcium in the soil and made is unavailable for the plant. This is just one example of the things we are starting to look at and try to understand why things are responding the way they are. Another aspect we looked at was soil pH and stratification in the soil. At 1.5 inches deep it was 6.2, and at 8 inches, it was 4.6. As you can see, the difference in availability of nutrients at 4.6 vs 6 pH is fairly substantial. Learning how we can change that soil pH deeper down is going to be something we start looking at.
Another tool we have been using is the Agronomy 365 app. If you don't have this app, I would highly encourage you to get out your phone and download it. It is a side company to Next Level Ag. They have an agronomy chat board where you can go ask questions to agronomists, put your soil samples on there, your tissue samples. It's a really open forum to have an agronomy discussion. A lot of good information is shared from all around the country using this app, so I'd highly encourage you to participate and to get on that.
The next step in tying together soil and tissue samples and nutrient availability, Next Level Ag uses their Agronomy 365 dashboard. Their protocol is to collect a soil sample three times a year, and during the season take a tissue sample at least five times from that same spot. We encourage you to do it every week. That data goes on their dashboard and we can overlay the two samples together. This helps you visualize what is available in the soil, what is being taken up by the plant, and what is that most limiting nutrient in your operation.
Another aspect to consider is the relationship from nutrient to nutrient. They interact with each other, and nutrient balance can effect your plants. The soil is dynamic, it changes every day, every hour. We've gone out and tested in the morning and then we go out and we test in the afternoon with these SAP samples and those values can change incredibly based on how much sunlight we've gotten that day, what the temperature is, etc. So in other words, these numbers change all the time. But it's important to understand what our balance is. The 365 dashboard gives us a driss level, which is the relationship from nutrient to nutrient. The nutrient that has the largest negative would in theory be your most limiting nutrient. The NBI (Nutrient Balance Index) shows that balance across all the nutrients. The goal would be to get this to 0. This type of measurement helps us to understand which nutrient is the most limiting.
There is also a charting tool that charts your tissue sample compared to a higher yield trajectory. We reviewed close to a dozen of our growers this past year using this tool and there were two nutrients that every grower was substantially lower on than they should have been: sulphur and calcium. Every year we get less and less sulfur from our rainfall and we need to be addressing our sulfur needs more and more in season.
Soil health is more than nutrition. 3.6% of total yield is NPK; 96.6% is carbon, hydrogen and oxygen. We went back and figured up how much we spent on our operation last year and it was over $500.00 an acre on this 3%. How much attention are we paying to this 96.6%? In the past we thought we couldn't do that much about it. Carbon and oxygen are two things we should start paying more attention to. Soil structure trumps nutrition nine times out of ten. How well drained is your soil? What's the soil flocculation look like? That soil structure is going to impact root development and oxygen in the soil. So how do we measure that? Water extractable organic carbon (WEOC) is the fuel that drives the engine. If that number is low, you don't have enough gas. You've got to get that water extractable organic carbon higher. It's part of that 96.6%. If we're not measuring that, how do we know how full our fuel tank is? Respiration is the rpms that tells us how fast that engine is going. It tells us where the throttle is at and how we adjust. One area we are starting to focus more on is how to change that respiration score. How do we get that cranking. That's what cover crops do, right? There are growers talking about making sure you have a living crop in your field every day that you have a temperature above freezing and having a living root in your soil all the time. It gets the rpm's cranking. Buying biological products, whether that's a seed treatment or a bug in a jug, all of those things are going to impact that respiration score. Understanding how to measure that and then what is that impact will do for our crop is huge.
One of the key takeaways that we learned this year is that too much nitrogen is a bad thing. This is probably one of the take home messages for every producer we work with. We have over applied nitrogen in the past and it has caused more harm than good. Too much nitrogen is a bad thing. The reason for that is over applying nitrogen without enough carbon will burn your corbon up and lower your WEOC score. It blocks the flow of nutrients in the plants. There is a cation-anion exchange that happens in the plant, and there is too much nitrate is blocks the other anions from being able to get into the plant. There has to be a balance. Too much nitrogen over stimulates the biology and then it dies. Too much nitrate is doing a lot of damage in our soil. A good rule of thumb, no more than 40-60 pounds in a single application whether that's preplant or fall applied. We know that is a huge challenge, but lets break it down a little.
To understand that nutrient balance is there's an antagonism and a stimulation. We all know that we need sulfur to go with nitrogen. Those are stimulation nutrients, they stimulate each other. But if you get that nitrate too high., it's going to block certain things. There's going to be an antagonism to potash. There's going to be an antagonism to copper, when that nitrate is too high it's blocking potassium from getting in the plant. Understand that that there's a symbiotic relationship and it's not all positive. If we go throw too much nitrate in the system, we block other nutrients from getting in the plant. Balance is more important than values.
Looking at the balance of these tissue samples versus individual values, one of the other notes that we've learned from this is that if you get sodium higher than potassium, the plant cannot distinguish between the two. For anybody that has high sodium in their water, we need to be measuring what that sodium is doing in the soil. There was a new field we just started working with in the Red River Valley, and the corn was shriveling up; we were irrigating and it just kept going downhill. We pulled some soil samples, and found the sodium was higher than potassium. The plant was taking in sodium instead of potassium, which is basically killing it
So those are things that that we've learned using the additional information that we can get on the Next Level Ag samples.
Conclusion
Nutrient management has huge potential to affect how your crop yields. As you can see, there is so much we know, but even more to learn. We are really excited about new technology and developments around agronomy, irrigation, and management of resources. If you have questions or would like to learn more, please contact us!
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