Some wheat fields are looking less green than we hoped for but not surprising due to the continued mini-monsoons we keep winding up with.  A good bit of the wheat crop is at the flag leaf stage meaning it is too late to add additional N at this point.  Nitrogen is not in an available form immediately upon application–sources will need a few days to incorporate and convert to forms the plant will use.   I know that a few folks are going to go ahead and fly on urea and some are considering spraying liquid N.  Liquid N can burn leaves- we are very humid and fairly warm right now.  Burning the flag leaf is not a good thing for the developing head later on and we do not recommend this.  Streaming liquid N on may injure less of the total crop vs broadcast spraying, but if it is windy this type of application still has the potential to cause widespread damage.

Nitrogen applied in March or April for the corn crop is largely still available although some nitrate leaching has occured at this point.  Data suggests that in a typical spring, 80% of ammonium nitrate converts to nitrate in 3 weeks or less while 50-70% of urea will do so.   We have had some cool temperatures, but soils have still been warm enough for fertilizer conversion to nitrate.  Nitrate N is subject to leaching with heavy rains but is not necessarily lost to the crop as long as roots can access it deeper in the profile.  Our crop is tiny and underdeveloped roots will not access deep N.  If fields were flooded/heavily saturated for 2 or more days, nitrate can convert to nitrogen gas and volatilize off the field reducing total N available for the crop.  It is difficult to guess how much we may need to supplement our sidedress rate.  Certainly an additional 20-30 lbs would not be out of line for fields that did not flood or pond for any length of time.  Consider sidedressing a bit earlier than normal if corn does not green up quickly with sunny days and drying conditions.  Your at-planting N may be beyond the reach of a young crop.