Why does my nitrogen recommendation change if I run it multiple times in a day?
- Field must be created.
- Seed must be placed on a field.
- A yield target must be set.
- Nitrogen templates created.
- Nitrogen plan placed on field.
- Run Nitrogen simulation.
When a nitrogen simulation is run, the next 8 day forecast is needed in addition to the 20 year normals and current crop year actual weather data.
The weather forecast is updated every 15 minutes by our provider (The Weather Company). So, if you run a simulation for a field multiple times in a day, you may see a change in your nitrogen recommendation based on a constantly updated forecast. Sometimes the difference may be minimal, but in other cases there might be “tens” of pounds difference based on how the forecast changes during the day for the next 8 days.
To illustrate this point, a significant rain event was tracked before it happened in the 2018 crop year (see the graph below). The day before the rainfall event, the predicted amount of precipitation changed from about 4.5” expected at 10:30am to about 1.75” at 3:30pm that same day. This could have made as much as 5 - 10 lbs. difference more/less at VT/R1 depending on other factors such as soil type, existing soil moisture levels, time of year when the rain event occurred, etc.
This was an atypical rainfall event in terms of the amount of rainfall, but it illustrates why we always want to get the most recent forecast for our nitrogen recommendations.