Manure is in it for the "long haul"
by Everett D. Thomas
The author is retired from the William H. Miner Agricultural Research Institute and now is a consultant for Oak Point Agronomics, Hammond, N.Y.
Manure's advantages go far beyond major nutrients as the organic matter in manure acts as a soil conditioner. It also adds secondary and trace minerals.
Before you empty your manure storages, give some thought not to where it's convenient to spread but where the nutrients in the manure are most needed. Very seldom are more nutrients needed in the field closest to the cow barn!
A few years ago, we did a simple spreadsheet analysis at the William H. Miner Agricultural Research Institute, Chazy, N.Y., to determine how far a farmer could profitably haul manure, using either a truck-mounted tank spreader or a tailgate spreader pulled by a tractor. Not surprisingly, on a per mile basis, the truck was much cheaper to operate. Labor cost also was lower because a truck takes less time than a tractor to make the round trip between manure storage and field. These results suggest that as long as the faraway fields need the nutrients more than near-by fields, you can drive a long way before the cost in fuel, equipment and labor exceeds the value of manure's nutrients.
On many farms, a 4,000- to 5,000-gallon truck-mounted spreader can haul manure at least 10 miles before costs approximate the nutrient value of the manure. And this only takes into account the value of the nitrogen, phosphorus, and potassium in dairy manure. The maximum distance that manure can be economically hauled also depends on the nutrient density of the manure, and this is primarily determined by how much water has been added from precipitation and water use in the barn including misters, alley flush systems, and how often waterers are cleaned. (If you dump waterers frequently -a daily chore on many farms - you might be amazed at how much water this can add to manure storages.)
Long-term fertility needed
Recent research has shown that crop yields are higher where there's high soil fertility plus a low rate of fertilizer versus low soil fertility plus a high rate of fertilizer. Therefore, how much bang you get for your fertilizer buck depends to a great extent on soil fertility before you apply any fertilizer.
We've long known this to be the case for soybeans, but it now appears to be true for other crops, as well. This stands to reason, since fields with a history of regular manure applications have nutrients distributed throughout the plow layer, while relying primarily on band applications of fertilizer (via the corn planter or grain drill) concentrates nutrients in a relatively small area.
Which field do you think would better tolerate a long stretch of dry weather: A field with nutrients concentrated in the top few inches of soil or one with nutrients distributed throughout the plow layer?
As the soil dries out, the nutrients in the top few inches of soil become less plant-available. Remember, roots can only take up nutrients that are in the soil solution. As an old agronomist said over a generation ago, "Roots ain't got teeth - they can't eat nutrients, they've gotta drink em."
Manure is a multivitamin
Because manure is considered a waste product, many farmers think that the nutrients in manure are less efficiently utilized by plants. Nothing could be further from the truth: The phosphorus and potassium in dairy manure, for instance, is just as available as these nutrients in commercial fertilizers such as diammonium phosphate (DAP) and muriate of potash. In fact, Quebec research found that the potassium in dairy manure was slightly more available than the potassium in 0-0-60 fertilizer.
Manure's advantages go far beyond the major nutrients nitrogen, phosphorus, and potassium. The organic matter in manure is a soil conditioner, and the secondary and trace minerals can reduce or eliminate the need for applications of these often expensive nutrients. Atmospheric depositions of sulfur, for instance, have fallen tremendously in the past 10 years or so, and will almost certainly continue to decline. We're now finding sulfur deficiencies where we've never found them before. However, manure is a decent source of sulfur, and where farmers routinely apply manure to fields, there's less chance that sulfur-containing fertilizer will be needed.
Dairy farmers import many micronutrients onto the farm, not just as fertilizers but as the minerals used in rations and those coming onto the farm in purchased grains. Some of these nutrients pass through the cow into the manure. Manure is, therefore, a multivitamin for soils and crops!
Dairy economists frequently use the milk:feed ratio as a measure of profitability in the dairy industry. It's no news to readers of Hoard's Dairyman that the milk:feed ratio has been at generally unprofitable levels for some time now. However, if there were such a measure as the milk:fertilizer ratio we'd see how much things have changed in the past few years.
Milk prices have been depressed, while fertilizer prices have risen dramatically, and I don't see this improving much in the coming years. Milk prices may go up somewhat, but the worldwide demand for grains is very high and grain reserves are at historically low levels. About 25 percent of Russia's wheat crop was destroyed, and U.S. No. 2 corn is crowding $5 per bushel.
Short-term, this is bullish for fertilizer demand and, therefore, for fertilizer prices. The worldwide recession dampened demand for fertilizers, so some products including DAP plummeted from their 2008 highs. It's now catch-up time for farmers who deferred fertilizer applications, and due to strong demand in the U.S., Europe, and South America fertilizer prices are on the way back up. Recently, DAP went over $500 per metric ton.
Higher yields and planted acreage will have a hard time keeping up with population growth, so feed and food demand will continue to put long-term pressure on fertilizer prices. Then there's ethanol! Therefore, in the future it will be even more costly for dairy farmers to apply manure on high-fertility fields and relatively high rates of commercial fertilizer on low-fertility fields.