3000 lbs of alfalfa hay X .17 crude protein = 510 lbs of protein. Nitrogen X 6.25 = crude protein. By taking 510 lbs of crude protein and dividing by 6.25 = 81.6 pounds of nitrogen in the fed hay. Only about 35% of the nitrogen in manure and urine is available to be used. The balance is lost to volatilization as ammonia.
Using 81.6 pounds of nitrogen X .35 = 28.6 pounds of nitrogen available to be used by growing plants from the fed alfalfa hay.
The availability for phosphorus and potassium in manure and urine from feed consumed is 100%.
To find the value of phosphorus and potassium in the fed alfalfa take 3000 X .003 = 9 of phosphorus and 3000 x .024 = 72 lbs of potassium.
In one ton of alfalfa hay, there are approximately 19 lbs of nitrogen, 6 lbs of phosphorus and 48 lbs of potassium that are applied to the ground in excreted manure where the hay is fed. The fertilizer nutrient value of these minerals at $0.60/lb of N ($11.40), $0.65/lb of P ($3.90) and $0.40/lb of K ($19.20) would in total equal $34.50 per ton. This value doesn’t include micronutrients and the organic matter in manure and wasted hay.
It is common to see weed problems develop on rangeland that cattle are fed on during the winter months. The nutrients from the hay are often concentrated in feed areas and the availability of nitrogen, in particular, in rangeland situations encourages weed growth. If hay is being fed, is there an opportunity to feed cattle on ground where the nutrients can be utilized for growing tame perennial or annual forages that would respond to the fertilizer?
Nutrients in hay have value. Finding ways to effectively utilize and recycle nutrients is economically beneficial. Strategically thinking about how to capture the value of nutrients in harvested forage is one way to reduce fertilizer prices for growing crops.
Source: University of Nebraska