My cousin the dairy farmer is frustrated with the increasingly stringent regulations about nutrient (read: manure) management. One of his favorite quotes is that while “city people” always blame farms for polluted water in Lake Geneva, that:
“The lake water was perfectly fine when there were 300 dairy farms and 10 houses. Now there are 10 farms and 3000 houses. The water quality is worse now. How can it be the fault of the farmers?”
I never argue with him on this point. But here is what I think.
Well, in 1940, there may have been 300 farms, but they generally had 20 to 30 dairy cows grazing 160 acres of land. Crops were grown rotationally around the property, but most of the land remained in sod. The cows, while walking, distributed their manure over the entire acreage. Since the sod absorbed water and prevented erosion and wash-outs, there was very little run-off.
Fast-forward sixty years. My cousin now has 1400 cows on 80 acres. The cows get a large share of their nutrients from grains and supplements, dramatically increasing the phosphorus content of their manure. 1400 cows produce a lot of manure - over 100 pounds per day per cow. So we are looking at 70 tons a day, or close to 26000 tons of manure per year. Since the cows are kept in confinement, their manure stays on concrete until a bobcat operator pushes it down the alley into a manure lagoon. The manure and all of its nutrients sit until the winter.
When crops are harvested for silage and hayledge, the manure is pumped into trucks and spread on the fields. Since the fields, particularly those previously planted to corn, are bare, there is nothing to prevent rainwater from washing the manure right down into creeks and into the lake.
Manure is a valuable addition to the land. I bring truckload after truckload of stuff donated by horse people to my garden every year. An organic system that does not use chemical fertilizers should shoot for five to ten tons of manure per acre per year. Given unlimited resources, many organic armers would love to go as high as 40 tons per year.
But one can go too high. If phosphorus, nitrogen, and potassium (the npk on your fertilizer bag) become to highly concentrated, they can “burn” plants and do them in. In an organic system, this is avoided by working in the manure bit by bit during the year, allowing the soil bacteria to incorporate the nutrients bit by bit.
In a mechanized field crop situation, the manure is spread at the very point that the soil bacteria is LEAST able to do its job - when it is cold. Bacterial action slows and finally almost ceases as the thermometer drops. And the manure is added all at once. So instead of being incorporated into the soil, it sits, frozen, under the snow, until the snow melts in the spring and drains all those nutrients into creeks and the groundwater.
So going back to the previous example, we have 20-30 cows dropping 350-500 tons of manure on 160 acres over an entire grazing season - averaging about 2 1/2 tons per acre. The bacteria begins breaking down each patty as it falls. When winter closes the pasture, the manure is set aside for spreading in the spring (one can drive wagons on sod).
The modern confined dairy, unregulated, might spread 300 tons of manure per acre - all at once. The manure has greater concentration of nutrients. It is spread in the winter so as not to disturb row crops, so bacteria doesn’t break it down so it can be held in the soil. bare earth allows the nutrients to leach faster. Snow melt accelerates the process. This is why state governments are beginning to require nutrient management plans so that overloading the carry capacity of the land is avoided.
This doesn’t even consider the fact that to make machine handling easier, the manure solids are mixed with liquid to form “slurry” so that it can be pumped through hoses. Sometimes the manure lagoons fail, spilling their poisonous contents.
Perhaps big dairy farms ARE responsible for water pollution.
But what do I know? As he would say, I’m just a city person.
