Originally Posted by Skipster
Maybe you've misunderstood Dr. Soldat's work. The actual research conclusions were that more N is taken up in warmer temperatures, so most of the fall application should be done before the first frost. This doesn't mean that none should be done later -- just that most of it should be done earlier. His work actually showed that spoonfeeding turf at 0.1 to 0.2# N/M every week for 6 wks beginning at the first frost was more beneficial than applying most of your fall N in a soluble form before the first frost. Also, don't forget that some N is still needed after the first frost, since photosynthesis will still be occurring through much of the fall.
This really confirms what many of have been doing for years -- using most of our fall N in Sept or early Oct, then using less afterward.
I don't think I misunderstood it at all. For years it was common practice to apply 1 lb of water soluble nitrogen in October to early November in the theory that the roots would use it to build carbohydrate stores. He went looking for research to prover this theory and he couldn't find much. Many of those ideas came from the central part of the country such as Ohio which has a much different growing season. He stated to me in person that if applying 1 lb of water soluble N it should be done no later than Oct. 1. He said you could apply a 1/2 lb up to Oct. 10th. Any N applied after those dates will result in 1/2 to 3/4 of the N volatilizing or leaching away before the roots can uptake it. You are correct that the plants still need N up until the ground freezes but I use at least a 50% controlled release product so the N is available until the ground does freeze. I believe his research was done using ammonium sulfate. Since I can't be on my customers lawn every week I asked if my idea of using a controlled release earlier in the fall would work and he said yes, it should.