Every once in a while, I get a chance to slow down and think a bit about some of the stuff that’s coming at us in ever increasing volumes and intensities. Nitrogen management, nitrous oxide emissions and the carbon economy are some of the issues that come to mind.
Global nitrogen use efficiency (NUE) is pegged at less than thirty per cent. With oversimplification, this means that of every 100 units of N applied, 70 are lost to the environment where the effects are mostly negative, and 30 units gets into the food, fuel and fiber produced in the world. Fortunately, the NUE is significantly better (50 per cent) in North America, but we can do better.
GET IT RIGHT
I know I have written about this recently, but it bears repeating. Nitrogen use efficiency is achieved by implementing the four Rs: the right rate at the right time with the right placement and in the right form. With the additional time to think, I realized I had forgotten a very important R and that would be the right balance of nutrients.
Here’s a more detailed breakdown of the four (or five) Rs:
1) Right Rate(s) — what crop are you growing, what is your yield goal, what is in the soil and what will be released = how much you need to add.
2) Right Time(s) — how close to seeding or yield/quality formation will the right rate(s) be applied. Are there any synergies that could be found/created?
3) Right Placement(s) — there are many options broadcast, banded (seed placed, mid-row, side band, dribble), foliar and various application combinations. What are the potential negatives? What are the SBU implications?
4) Right Form(s) — ammonium, urea, nitrate, organic, anhydrous, liquid, dry and various combinations are all form choices. How about ESN, Agrotain, N-Serve and combinations of all the above?
5) Right Balance — When I was a teenager, I dreamt of owning a ’55 Chevy two-door with a tricked out 350 engine. The four Rs are like a tricked out 350. You can do everything just right to get the engine at top performance, but if the tires are flat you will only make a bunch of noise. Inflating the tires is about the right balance. Making sure there is oil in the engine, in the transmission, in the rear end (with 4:11 gears), etc., is about the right balance. See what I’m getting at?
For crops, let’s pick canola as an example. You can have the four Rs nailed but if your sulphur (S), potassium (K) or boron (B) is not available in sufficient quantities then you have a tricked out engine and a car with two flat tires that
goes around in circles very fast.
The graph summarizes some 2010 data from a replicated canola trial in Ontario. In this trial, N was applied at various rates (0, 45, 90 and 135 lbs. N/ac.) with and without S (18 lbs. S/ac.). Without applied S, increasing rates of N dramatically decreased yields. By adding a moderate amount of S, they significantly increased yields and NUE.
In which instance are we achieving the goal of the four Rs? When we are in balance. Now, answer this please. How much S does a 60 bu./ac. canola crop need to access? The answer is minimally 33 lbs. S/ ac. Imagine if the researchers had applied 36 lbs. S/ac. instead of only 18, what would have the yield potential been? Hard to say definitively, but we would expect even higher yields, better NUE and positive environmental impacts.
Global nitrogen use efficiency is pegged at less than thirty per cent, meaning that only 30 lbs. of every 100 applied is actually used as intended