Question about Applying Ammonium Sulfate to Peanuts Early in the Season

In research from many years ago we found that unless there is a true nitrogen (N) deficiency, there is no value in applying nitrogen fertilizer.  A clear nitrogen deficiency generally only occurs when peanuts have not been in a particular field for many many years or never at all and either inoculant was never applied or something negative happened to the inoculant before or during the planting operation.  There are numerous reasons why inoculants fail to perform and we go into detail on reasons in 2020 Peanut Information.  With this said, there are occasionally times when some starter N might help.  Peanuts grown in sandy fields often struggle to grow rapidly to shade the pegging zone, and a modest amount of N can help promote growth to help in this case.  The value of the rapid growth is so that soils are cooler (shaded) in the pegging zone and fewer of the first pegs are destroyed if soils are very hot.  But, our general recommendation is to hold off on ammonium sulfate until you know you have a true N deficiency.   If peanuts begin to have a pale or yellow cast early in the season look at roots (dig them up – don’t pull up plants) and see if nodules are present and active.  If not, add ammonium sulfate to these fields as soon as possible.  Peanuts need as much N as corn, so an inoculant failure becomes very expensive to address.  A single application of 500 pounds/acre ammonium sulfate is recommended just as soon as you have determined that the issue is an N deficiency.  Sometimes when soils are wet for a prolonged period of time nodules are not active.  Once soils dry they become active again.  Sometimes we apply ammonium sulfate to areas that have water issues and not N issues.