Farmers were literally raising a stink about high fertilizer costs all last year. Ironically, manure helped squelch that stench.
Although the nitrogen price is now at a more reasonable level, manure from feedyards and other confined animal operations helped many grain and cotton producers cut N costs by 50% or more in 2001. For a $12-15 cost, feedyard manure supplied about 100 lbs of N to their fields. The same amount of anhydrous ammonia would have cost about $30/acre last spring.
The anhydrous rate was based on a whopping $400/ton cost to farmers when natural gas prices swelled to $7-10 per 1,000 cu ft. That cost crippled many irrigation farmers and ag-related industries, including fertilizer companies. And the supply of fertilizer was tightened by companies that chose to reduce their output due to the high-priced gas.
“It doesn't take long to see how using feedyard manure can really help lower fertilizer costs,” says Raymond Schlabs, who farms corn, cotton and wheat in Hereford, TX. “We've used straight manure applications in the past and currently apply composted manure. Both provide good nutrients for our crops. And with the high price of anhydrous this past year, we were much better off.”
What's so fragrant about feedyard manure as a fertilizer? Just 1 ton of manure at 35% moisture has more than 25 lbs of N. “We can put down 15-20 tons of manure and have enough N for three to four years,” says Schlabs.
There are also more than 15 lbs of phosphorus per ton of feedyard manure. “The P is a bonus,” says Brent Auvermann, a Texas A&M University extension ag engineer who specializes in animal waste control.
Another 21 lbs of potassium, 23 lbs of calcium, 7 lbs of magnesium, 25 lbs of iron and a trace of zinc are in just 1 ton of manure. Unfortunately, about 5 lbs of sodium, which can harm soil, are in that ton, plus excess amounts of P and other nutrients that may build up.
Auvermann says the amount of manure needed will vary from field to field, depending on the nutrients called for from soil test data. “Soil tests are a must,” he stresses. He adds that, in most cases, an irrigated corn crop yield of 200 bu will require approximately 240 lbs of N, which equates to about 10 tons of manure, if there is no residual in the soil.
Schlabs, who farms with his son, Ray Jr., switched to narrow-row, 20” corn and cotton several years ago. Minimum tillage, with crops planted into stubble or stalks left from the previous crop, has proved beneficial, since he has center pivot irrigation with low-pressure nozzles.
To his advantage, the farmland is within a few miles of a regional feedyard, one of 100 or more that populate the Hereford and southwestern Texas Panhandle area. Trucks equipped to haul 15 tons of manure and spread it over fields are plentiful.
Transportation costs have always been the key to whether manure was economical. Since 1995, the average industry cost of feedyard manure has been $2.14/ton, plus 12¢/ton mile. The primary resistance level is about $3/ton when N costs averaged $150-200/ton.
That made the manure economical for fields within 7-10 miles of a feedyard. But with the increase in N prices to $400/ton, that distance stretched to 20 or more miles. “That's only for the N value of manure,” says Auvermann. “Every 20 lbs of P needed and supplied by manure reduces the cost of manure by about $5/acre.”
Schlabs and Auvermann note that some of the disadvantages of manure have been reduced substantially. There is a much lower level of chipped concrete from feedbunks and other trash. There's also been a major reduction in weed seeds.
For Schlabs, composted manure is now preferred because it can be incorporated into the soil more efficiently (see chart for compost nutritional values). “When we apply compost, we also apply a little liquid fertilizer at a rate of 32-0-0,” he says. “It can easily be applied through the pivots (with fertigation).
“There's also less compaction from manure trucks driving across the field.”
His cost for applying 2 tons of compost is about $30/acre. “In most cases, 2 tons will work for one season,” says Schlabs.
Auvermann, however, says there can be drawbacks with compost. “Compost is an excellent product, but because of the composting process in which manure is turned, you're losing nitrogen,” he says. “That must be taken into account.”
Auvermann says the fertilizer value of manure from dairy, hog and poultry operations is also beneficial to many farmers nationwide. To determine if such applications are efficient for a particular field, he recommends that growers consult their regional extension agronomists or animal waste specialists.