Feeding hay for better soils

Jesse Bussard

On the flip side, Gerrish pointed out, hay can also be a fertility source for organic producers or those desiring to transition away from synthetic fertilizers to build soil health.

“Hay as fertilizer provides a full nutrient package rather than just NPK,” Gerrish said.

Gerrish noted that in much of the U.S., hay can be bought at a lower price than most farmers would pay to produce and harvest it on their land. This includes the value of all the nitrogen (N) and minerals contained in that hay.

According to Gerrish, on average, every ton of hay harvested from a pasture removes approximately 40 to 60 pounds of N, 6 pounds of phosphorus (P), and 30 to 50 pounds of potassium (K), along with a wealth of minerals. At today’s fertilizer and mineral prices, a ton of hay contains nearly $60 in fertilizer value.

“You are either getting your feed or your fertilizer for free when the price of the hay is less than the fertilizer value it contains,” Gerrish said.

Spread it out

The key to using hay to improve soil health lies in feeding it uniformly over pastures. The trick to doing it right, Gerrish said, is to be aware of how many nutrients are in each bale being fed. Use this information in planning daily feeding so appropriate levels of nutrients are applied. This will help to avoid circumstances where too little is fed and no benefit is achieved, or worst case, too much is fed and the soil and environment are overloaded with excess N.

“When you feed hay for fertilizer, we often think of it as a way to reduce the need for purchased fertilizer, especially nitrogen,” Gerrish said. “But have you thought about how much nitrogen you may actually be applying when you feed hay?”

For N specifically, Gerrish explained, the amount of N in hay is directly tied to its protein content. Protein, on average, contains 16 percent N. Additionally, he said, it’s important to note that grass hay may have less protein than the livestock being fed require while legume hay generally has much more protein than needed.

If the hay provides just what the animal needs in terms of protein content, then about 50 percent of the N will be excreted in the feces and urine. In general, livestock excrete 85 to 95 percent of the N consumed, indicating they are getting more protein than required.

“Fecal N content changes very little as dietary protein level increases,” Gerrish said. “Nitrogen 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.”

Have a systematic approach

In reality, almost all excess N ingested by an 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 and readily available N fertilizer. So, when managing hay feeding for a targeted N application rate, focus your attention on urinary N.

“Having a systematic approach to hay feeding is a critical part of maximizing the nutrient benefits you get when feeding hay; it’s a big piece of your pasture fertility program,” Gerrish said.

To help visualize this, Gerrish offered this example.

There are 250 cows in a herd and they are being fed about 30 pounds of hay per head per day for a total feed requirement of 7,500 pounds per day. There will be some waste, so he rounds up the amount fed to 4 tons of hay per day.

In this scenario, hay that is 14 percent crude protein (CP) will return about 31 pounds of urinary N for each ton of hay fed. At an N target application rate of 120 pounds per acre, cattle could be fed hay one day per acre to reach the target rate.

Another factor to consider when feeding hay in this manner, Gerrish noted, is manure distribution. In his experience, when feeding hay on snow-covered ground, he’s found typically 80 percent of the manure falls within 15 to 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.

Have a plan

Based on this premise, plan hay feeding to improve soil health accordingly. Using the 14 percent CP hay example and needing to cover one acre every day, the daily feeding regimen should cover a strip one-half mile long. In this example, hay could be fed for 80 days on an 80 acre field to fully fertilize that pasture at 120 pounds N per acre.

“It will take a few tries to figure out how fast to drive your pickup when unrolling hay, or how thick to make your flakes off the big square bales, or the needed windrow width coming out of the bale processor,” Gerrish said. “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.”

Other final tips Gerrish shared to those interested in giving the practice a try are to always purchase weed-free hay when buying off the ranch. He also recommended producers have a provisional plan for when they might not be able to unroll or flake hay on the target area due to excessive mud or snow.

This article appeared in the April/May 2019 issue of Hay & Forage Grower on page 35.

Not a subscriber? Click to get the print magazine.