Most parts of Ohio have had an excellent fall and early winter time period for manure application. The long fall window to apply manure should reduce the amount to be applied during the winter months. A few farmers have asked how much of the nitrogen in the fall-applied manure will be available for the 2016 crop.
Currently, most of the nitrogen in the fall applied manure should be where it was applied. The November and December rainfall data for the Ohio Research and Development Center (OARDC) branch at Hoytville shows 1.29 inches of precipitation (4.3 inches is normal). The rainfall data from the OARDC western branch at South Charleston to date is 2.69 inches (5.3 inches is normal). The low rainfall amounts will allow the manure to stay put for a longer time period.
The organic portions of the manure nitrogen will need warm soil temperatures to mineralize next year. Therefore, we would generally consider the organic portion to still be present through the spring planting season.
The ammonium nitrogen portion of the manure will eventually be broken down into nitrate nitrogen through a process called nitrification. Soil temperatures below 50 degrees Fahrenheit will slow this process but not completely stop it. In the nitrate form, the nitrogen will be more susceptible to leaching if we have a wet spring. If the ammonium nitrogen was applied to wheat or a growing cover crop, then much of it has been captured and used to produce plant mass. Eventually it will become organic nitrogen once the crop is harvested or killed.
It’s way too early to even guess how much of the manure nitrogen applied this fall will be available for the crop in 2016. Two years ago we had a long cold winter but still lost most of the fall-applied manure nitrogen when spring was wetter and planting was later than normal. In order to make a good determination, farmers will need to evaluate fields once they see what the weather does next spring.