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The ‘dirt’ on ash and milk

There are multiple nutrients in forage that compose a portion of ash measurement, including dirt that mixes in during harvest.

Tom Kilcer

January 19, 2024

5 Min Read
A forage harvester chops and blows hay into a wagon
HARVESTING FORAGE: A forage harvester chops and blows hay into a wagon being pulled by a tractor. Forage has calcium, magnesium, potassium and other nutrients that compose a portion of the ash measurement. Unfortunately, forage sometimes has a significant amount of plain dirt mixed in during harvest. SimplyCreativePhotography/Getty Images

Forage has calcium, magnesium, potassium and other nutrients that compose a portion of the ash measurement. Unfortunately, forage sometimes has a significant amount of plain dirt mixed in during harvest.

This dirt is either incorporated from mower knives cutting too close and digging into the soil; from dirt incorporated by tilted knife updraft; or from dirt incorporated by tedders, rakes and improperly run mergers.

Cows don’t milk well on dirt. Haylage ash levels run between 9% and 13%. Does this have an impact? We ran that question by nutritionist Dr. Charlie Sniffin. While rations were the same, he changed the ash level in the haylage. In his calculations, we lost 1.9 pounds of milk per cow per day when the ash level increased 2%. The impact is from a direct decrease in digestible material.

A second factor is the biased numbers entered into the ration in the first place. The apparent neutral detergent fiber concentration will go up, shortening the animal on effective NDF with metabolic consequences. This is all before we even consider the impact of endotoxins brought in with the soil.

With milk running over $21 per cwt, the 2% ash level change on 100 cows is a direct loss of $12,170. On 500 cows, it is $60,848. For 1,000, cows it is $121,695. Ash is a hole in your pocket with the money running out.

Where does ash come from?

Our first thought is farms that suffer flooding. Vermont had a lot of experience with this when Hurricane Irene slammed the state. Farmers tried making silage with buffered propionic preservatives, various inoculants and just ensiling. One of the workers in the area said the silage went in and came out smelling like sewage. The cows crashed, and some even died.

Flooded haylage needs to be chopped down on the field to allow new growth to emerge. There is no way to save it. Corn silage is more deceptive. It can look fine from the road, but the bottom quarter-inch, half-inch or three-quarter-inch may have been flooded.

Each leaf axis has a pocket of dirt that will not be removed by rain. If the chopper can’t cut above the flood line, then mow it back on the ground. Farmers who thought they could get away with this paid an enormous price in lost production and lost animals.

One farmer I know did combine some of the grain with the fan set at full blast to remove what may have gotten in the ear. Even then he had to deal with endotoxins and feed a high rate of binder. Flooding certainly is the 500-pound gorilla in the room.

But what about the sneaky rats that do much more damage year after year? Ash may look minor on the forage test, but it is a huge money drain.

Is your mower too low?

For hay, the problem starts with the mower. Most are set close to the ground to get more yield and more of the down material. Down material has little or no nutritional leaves and is usually covered in mold. Every field irregularity means more dirt in the forage.

Farmers get impressed by a clean mowing job. The mower is designed with knives angled downward. This combined with coned drive drums will create a vertical vortex that sucks everything up and incorporates it into the forage. Roll and tine conditioners ensure it is mixed in the windrow.

Dealers often set the machine to mow very close to the ground. Cutting height set low will cut more material, but the price is more ash. One farmer I know who bought a new machine simply dropped the pin in and started mowing at the original setting.

His nutritionist complained that, despite using inoculant, there was tremendous mold in the forage. His sample showed a 17% ash level. Every ton had more than 120 pounds of dirt.

The farm lost 10 pounds of milk per cow per day. On 100 cows, the loss was over $54,900. He paid for the machine twice, once by writing the check and once in lost milk sales.

Consider raising the cutter bar

Raising the cutter bar will reduce alfalfa yield by 300 pounds for every inch. What is lost is the lower portion of the stems with no leaves that have digestibility that is about equal to the bushes at the edge of the field.

In addition to improving forage quality, raising the cutter height leaves the new shoots on the alfalfa for rapid regrowth after the forage is removed. This can rapidly increase the next yield and reduces the potential for weeds. If you missed your harvest window and the quality peak has gone by, you can also recover some of that by mowing higher.

The forage you harvest will be the higher-quality equal to the harvest window you missed. Raising the cutter bar is critical for survival and a high yield of cool-season grasses.

Grasses regrow using the existing leaf tissue, not from root reserves like legumes. Cutting grass too close to the ground leaves no regrowth, and the stand can quickly die out. Multiple studies have found a 4-inch cutting height is critical to both survival and total yield. If you pull out after harvest and the field is not still green, you screwed up future yield and replaced it with weeds.

For mixed grass or legume stands, the more grass you have the more critical that the cutting height be correct.

Use flat knives

Switching the knives on a disk mower from tilted to flat will reduce the “vacuum” effect of sucking. Lodged material that is left behind has very poor feed value, so leave it there.

Mowing without conditioners — that our wide-swath same-day haylage research found were not necessary and counterproductive for rapidly drying haylage — will allow any soil to drop out the bottom of the swath and not make it to the silo. The higher stubble gets the forage off the ground, which in a wide-swath, same-day haylage system speeds the drying and preserves more digestible material for the cow.

It allows for tedders, rakes and mergers to move the forage without rooting in the ground, mixing more ash in the crop.

Finally, research has found that mergers, run properly, will move the wide swaths to a windrow without adding more soil and possibly even reducing what the mower put in.

Look at your haylage samples. Every point of extra ash is money down the drain in lost milk and indirectly by poor fermentation.

Kilcer is a certified crop adviser in Rutledge, Tenn., formerly of Kinderhook, N.Y.

About the Author(s)

Tom Kilcer

Tom Kilcer is a certified crop adviser in Kinderhook, N.Y.

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