This is Part 2 in Jim’s series. If you missed Part 1, here you go!
When you feed hay for fertilizer, we often think of it as a way to reduce the need for purchased fertilizer, especially Nitrogen (N). Have you thought about how much N you may actually be applying when you feed hay?
It may be more than you think.
Let’s Look at How N Moves From Fed Hay Back to the Soil
The amount of nitrogen in hay is directly tied to the protein content of the hay. Protein on average contains 16% N. Grass hay may have less protein than the livestock being fed require while legume hay generally has much more protein than required.
If the hay is just what the animal needs in terms of protein content, then about half of the N will be excreted in the feces and half in the urine.
Livestock will generally excrete 85 to 95% of the N consumed.
Fecal N content changes very little as dietary protein level increases.
N is slowly released from manure piles as they decompose. feces breaks down relatively quickly in warm, wet environments and very slowly in cool, dry environments.
Almost all excess N ingested by the animal when protein content of the feed exceeds the animal’s requirement is returned to the soil via urine.
Urinary N is a highly soluble & readily available N fertilizer. When managing hay feeding for targeted N application rate, urinary N is where we focus our attention.
This table shows how much urinary N is returned to the soil depending on the protein content of the hay.
When you decide how many bales of hay you will be feeding on an acre of pasture, this table can help you decide.
If you set a target amount of N to apply, you can determine how many bales per acre it will take to accomplish that application rate. You can see the number of bales to feed per acre will vary greatly depending on the quality of the hay being fed.
Do you have a nutrient management plan or are you missing a great opportunity and wasting resources?
In Part 3 of the series, Jim provides some background to help you figure out a plan to manage the nutrients from your hay feeding.
What if you have pastures full of horses, instead of cows? Do the same calculations apply? I board horses in open irrigated pastures in SW Montana and have always wondered how much N goes back into the ground after a fall and winter of feeding. There are mixed opinions from locals about this.
Yes, the same basic relationship holds for horses as cows when it comes to retention & excretion of minerals.
The big difference is in redistribution patterns. Horses do have a much stronger tendency to concentrate manure in particular areas.
Shortening the time period horses are in a particular area will help with distribution.
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