Originally Posted by Smallaxe
Frozen solid is when I believe that the fertilizer isn't going to be used at any level and also when the dormancy period is using very little water in metabolizing its own life processes...
So with frozen ground being the zero fertilizing usage(0%), at what percentage of the fertilizer will be used when soil temps are below 50 degrees F.???
What percentage usage at 40 degrees F.???
Our last mowing was before Halloween, so we know that the tops stopped growing then, but how long will the roots continue to bring in new N beofre it stops altogether???
Usually, when pale green plants bring in new fertilizer AND adequate moisture, there is a definate color change... Here in Centro Wisco I've never seen a color change with fertilizers applied after Oct. 3rd or there abouts...
Even then it takes a couple of weeks for the change to be noticeable, so I should assume that the plant wasn't actively utilizing that NPK until it was broken down into useable form...
Our ground is not frozen as of yet.
As the soils here get colder, less urease activity will let more of the Urea, still in it's non-ionic form be absorbed by the grass roots.
The amount of Urea that DID become Minerilized by the Urease in the colder soils to the Ammonical form of Nitrogen is a Cation and will be held to Anions in the soil and will be available next spring when the soils warm back up.
Then Ammonical N will be converted to Nitrate Anion and be in the soil as a solution and can be used directly by grass roots.
We apply late season N partly for Nitrogen available now, and also for next season.
Late season N applications on our Cool Season Turf means we don't have to apply N with our 1st Round application next spring.
It works, we just have to stick to our new Lower Nitrogen Rate rules, here in New Jersey.......This will allow for less runoff and pollution potential from high rates of N.