3 Things to Consider Before Applying Fall Anhydrous

Many growers will head to the field this fall to apply anhydrous, in the interest of spreading the workload and saving money on input. Here are 3 things to consider before applying anhydrous this fall:

1. The weather next year – You’re probably asking yourself, “who in the world knows what the weather is going to be eight to nine months from now?” The answer, of course, is no one. With that in mind, how can a grower make a decision today about how much nitrogen he has lost or what his crop conditions will be next year? Think about this, eight to nine months from today your corn crop may still require up to 50% of its total N.

  • How much rainfall will the area get in May and June?
  • Will it be a year when a large amount of N is mineralized from organic matter?
  • How much nitrogen will be lost to denitrification or leaching?
  • Will I have a huge crop that can benefit from supplemental N during the growing season?
  • How quickly will the soils warm up in April and begin converting the ammonium to Nitrates?

If you can answer all these questions today, then applying 100% of your nitrogen in the fall is certainly a sound strategy. If you can’t, then perhaps applying a base rate of N (50 – 60% of your anticipated total N needs) in the fall and then adjusting the final application according to the growing season might be a better path to take. By splitting your total N, you are buying time to make better decisions according to the weather and potentially exposing less nitrates to denitrification or leaching into the environment.

2. Your investment strategy – I know, this has really taken a turn for the sublime, what does an investment strategy have to do with anhydrous application? When you invest funds, you likely diversify when possible. Perhaps you invest some in stocks, maybe some in lower risk bonds and perhaps some in hard assets like gold or land. When you think about how you invest you diversify to spread risks. So, why would you consider only one item in your nitrogen portfolio that assumes quite a bit of risk? By applying a partial base rate and gathering information you are essentially diversifying your portfolio and lowering your risk of making an errant nitrogen decision.

3. Agronomic considerations
Temperature: Everyone understands the importance of waiting until soil temperatures drop to below 50 degrees to help slow the conversion of ammonium to the nitrate form. But make sure to check soil temperatures and don’t simply assume.
Drainage: When choosing fields for fall application of N drainage should be a prime consideration. Poorly drained fields or fields high in clay content are more prone to denitrification during the growing season next year. Applying all of your nitrogen to those fields now can expose too much nitrogen to loss next year. The use of a nitrification stabilizer is a sound idea for fall applied nitrogen to help slow the conversion to the nitrate form.
Ground conditions at the time of application: Soil that is too wet can smear at the knife. In that case, the anhydrous can actually work its way back up the knife slot closer to the soil surface. When this occurs the ammonium is closer to soils that will warm up faster in the spring and convert more quickly. Soils that clod up during application can create air pockets that will also allow the anhydrous gas to move towards the surface.