The Agronomists, Ep 2: Greg Stewart and Jeff Schoenau on nitrogen management

Nitrogen use drives growth and crop yield — it’s also expensive and prone to being lost from the soil. There’s so many combinations of the right rate, place, form, and time, that nitrogen management is always a hot topic for discussion.

This episode of The Agronomists features Greg Stewart, lead agronomist of Maizex Seeds, and Dr. Jeff Schoenau, soil fertility professor and strategic research chair at the University of Saskatchewan’s Soil Science department. Soil fertility unites, and east meets west (literally, because Jeff and Greg have never met before) in this second episode. (Summary is below)

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• The topic of N and management, it’s broad, there’s a lot of strategies to choose from
• To do a good job of N management, there’s a lot of components to integrate, but mainly the 4Rs and weather
• The N cycle can be over-simplified at times, but how Schoenau likes to approach it is the 4Rs: source, rate, time, placement
• Margins are tight, want to apply N as effectively as possible, how do we get that N into the plant, and not in the air or running off in water
• VIDEO: John Heard in this Corn School, great graph, corn N uptake broken down by plant part, different types of N application
• Dribble band technology has to be low and slow, get that placement right
• Split applications in cereals is starting to emerge in the west, some at seeding, if there’s a high yield potential, get out and put another application on, the earlier it goes on the more it’ll go towards yield, rather than protein
• Split apps generally came out at the “top of the heap” when it comes to polymer coated urea in trials, says Schoenau
• Nitrification inhibitors can be a good fit if you plan on putting down anhydrous ammonia, be sure to get closure of the injection channel, otherwise ammonia will volatilize
• High OM, high clay, too much water, are all factors to consider when applying
• ESN: slow release benefits can be hard to quantify, it’s about the environmental conditions
• Nitrification inhibitors are effective under high loss scenarios (warm temps, moist or saturated soils, heavy clays), but under low loss scenarios or environmental conditions, not that much benefit
• VIDEO: Peter “Wheat Pete” Johnson in this Wheat School, split nitrogen on wheat makes you smarter
• Schoenau agrees with a split app from a risk standpoint, get it on early, unless you want that protein if you already know the yield will be there. With dribble-banding, Schoenau’s a fan. 30 to 50 lbs on brome-grass stand nearly doubled the yield and increased the protein. Beneficial to have that rain afterwards to move that N further down.
• Stewart, is it different for corn? Split-app is a decision that comes down to timing: planting and side-dress, or planting, side-dress and tasselling. Spoon-feeding? “A split-app isn’t necessarily going to add that much yield to a corn crop” says Stewart
• Another application of N? Well how much? It can be confusing.
• Humic acid? The major influence that humic acids have on plants is through root growth, says Schoenau, but wouldn’t have a direct interaction with N fertilizer in soil. In a fert band, perhaps some root stimulation.
• UAN or Urea? Liquid or granular? It has to get into the soil, somehow. It’s a logistical and operational concern, mostly, but beyond that there’s no difference really (in the west or the east)
• Retro VIDEO: Matt Gosling, Premium Ag Solutions, about tissue testing
• N losses as a function of soil texture, polymer coated ureas could be effective, but not generally in a broadcast situation, you’ll still have losses
• N-deficiency symptoms early in the season, research being done in Ontario. Symptoms, chlorosis of old leaves. In canola it might be purpling of leaves.
• Supply of N early on supplied at seeding time, excellent equipment for placing N. Seed bed utilization can dictate your maximum safe rates of N-placed N. Depth? If it’s urea, at least an inch below the surface. Shallow banding can cause increased volatilization of urea.
• N-balance, think about P, K, and S as well. It’s all part of a package.
• Wet soil, followed by dry out, competition for adsorption sites, not good
• Other ways to “gain” N from the soil? Pulse crops of course! For some legumes a little bit of N added at seeding (soybeans) is beneficial, but in general, pulse crops don’t need any N fertilizer.
• When it comes to N in a crop, what’s the number one mistake made? For small grains or oilseeds it’s how much N farmers put on in the seed row along with other nutrients, don’t push it. For corn, it’s keeping your yield expectations and soil type centered, and that N application rate isn’t a bullseye target, it’s moving and that’s ok.

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