Nitrogen fertilization of cereal grains for forage is important for both yield and quality. Using an application method split between the spring and fall is important and can increase yield and tillering, can help spread the risk of nitrogen loss and improve the nitrogen use efficiency. Knowing what your target yield is will help you determine how much the split application will be.
When fertilizing in the spring it’s important to have the correct timing and apply the nitrogen as the crop breaks dormancy. This allows there to be less of a chance for runoff and leaching and the ground is not frozen allowing the nitrogen to move into the soil to be utilized by the crop. Dormancy will break at different times in the spring depending upon the species grown. Cereal rye and triticale will green up first, while wheat and barley will be much slower. Nitrogen applied in the fall or split between the fall and spring will result in more constant forage production throughout the season compared to one spring application, though, spring applied nitrogen was found to increase yields up to 200lbs/ac compared to other methods based on work done in Oklahoma.
In recent research studies we have found that in order to optimize yield you need to add at least 30lbs of nitrogen in the fall. To help determine a realistic yield potential, look at the yield from the past five years, take out the highest and lowest yield and average the remaining three yields. This will should reflect a realistic yield potential to help determine the optimum nitrogen rate. We have found that crude protein in cereal rye was significantly increased by a 25lbs increase in spring nitrogen application regardless of the fall nitrogen rate. The dry matter yield can be increased by using the fall and spring split application method. Our studies have found that 20lbs of fall nitrogen had a significant increase in cereal rye yield of at least 1 ton of dry matter. The addition of 20 more pounds of spring nitrogen to the current recommendation of 50lbs can significantly increase the dry matter yield by half to 1 ton.
The crude protein levels can also be improved through split nitrogen applications. The spring nitrogen application is the primary driver of crude protein, one of our studies showed that an application of 70lbs of nitrogen has been found to increase crude protein. Though, one of our studies shows that 90lbs of fall applied nitrogen can statistically increase the crude protein. Other quality factors such as total digestible nutrients (TDN) can also be affected by nitrogen fertilization. In our research, TDN in cereal rye was found to be negatively affected by higher nitrogen rates but was not influenced by fall nitrogen treatments. Applying nitrogen in the fall has also been seen to increase neutral detergent fiber (NDF) compared to trials where no nitrogen has been applied. This may be due to slightly more advanced growth stages at harvest when the fall nitrogen was applied compared to only spring nitrogen.
Another thing to be mindful of when applying nitrogen fertilizer is your soil type. Sandier soil may require higher nitrogen rates compared to loamy or clayey soil due to lower water holding capacity and organic matter levels. Drainage within your field is also important, soils that are waterlogged in the spring during critical periods of growth and development can reduce the yield and maturity, and there could be a significant portion of applied nitrogen lost due to denitrification
To help make management decisions a few tools can be used to measure canopy cover. Two examples of tools to use are Normalized Difference Vegetation Index (NDVI) and Canopeo. NDVI is a sensor that is used in a non-destructive way to estimate the biomass’s nitrogen content in our studies and others, NDVI has been found to be equal or superior to other indices in predicting percent ground cover. Canopeo is an automatic color threshold image analysis tool to determine ground coverage. One known limitation of Canopeo is the need to keep the camera at an adequate height above the canopy. A forage analysis should also be used to determine the nutritional value of the forage for livestock performance. Utilizing the crude protein content of your forage test, if you know your yield per acre can allow you to calculate if you removed all the nitrogen you applied to your forage. Knowing the nutritional levels of a feed will help you make better decisions of what to feed and if you need any supplements.