The most difficult task for any farmer and crop adviser who is developing a N management plan is estimating the fertilizer and/or manure N rate for the expected crop uptake demand. While crop N uptake demand can be estimated based on a three to five-year yield history, knowledge of expected uptake (and removal) at the targeted crop yield, new crop genetic yield potential, and the provision of other essential nutrients and adequate plant protection ... the most unpredictable factor that complicates such estimation is the weather.





