Reprinted from On Pasture.
Having a systematic approach to hay feeding is a critical part of maximizing the nutrient benefits you get when feeding hay is a big piece of your pasture fertility program.
We have already seen in the previous post the amount of urinary N that is returned to the soil with each ton of hay fed. We know the amount applied depends on the protein content of the hay. Now let’s look at how you manage the feeding rate.
Let’s Do the Math on Hay Feeding for a Targeted N Application Rate
Remember urinary N is readily available for plant use and is also the form of N that is most likely to be lost to the atmosphere as ammonia or leaching after conversion to nitrate in the soil.
In this example we have 250 cows in the herd and are feeding them about 30 lbs of hay per head per day for a total feed requirement of 7500 lbs/day. We know there will be some feeding waste, so let’s round it up to 4 tons of hay fed per day.
Referring to the table in Part 2 of this series, we know hay at 8% CP will return about 11 lbs of urinary N and 11 lbs of fecal N for each ton of hay fed.
If our target rate of N application is 120 lbs/acre, we could feed on one acre of three days.
What if we have a hay that has protein well above the requirement of the animal?
Dry, pregnant beef cow only needs 7-8% CP. Now we are feeding a 14% CP hay so all the excess N is going to come out in the urine.
Now our urinary N rate per ton of feed is about 31 lbs, so we can only feed one day per acre to apply our target rate of 120 lbs/acre.
Now, Spread the Manure and Urine Across Your Pasture
While we would like to think that if we feed hay on our pastures, the cowsill s run all over and poop all across the field, they do not.
When we have measured manure distribution when feeding hay on snow covered ground, we find typically 80% of the manure falls within 15-20 feet of the feed line. Most of the rest is dropped between today’s feeding strip and the stock water. Very little is returned to the pasture at large unless there is residual grass the cattle are picking at.
Based on the premise that most manure falls within 15-20 ft of the feeding line, we can plan our hay distribution accordingly.
Using the 14% CP hay example and needing to cover one acre every day, we plan our daily feeding to cover a strip one half mile long. In this example, we would feed for 80 days on an 80 acre field to fully fertilize that pasture at 120 lbs N/acre.
It will take a few tries to figure out how fast to drive your pickup to unroll hay or how thick to make your flakes off the big square bales or the windrow width coming out of the bale processor.
The point is you can get a lot more fertility value out of the hay you are feeding if you approach that daily chore with a firm objective in mind.