When Wisconsin began changing its rules two years ago to require manure application rates based on phosphorus (P) tests instead of nitrogen (N), Walter Meinholz was ready. He'd already lined up additional land to rent — and in some cases has other crop growers use the manure from his 2,400 dairy cows for custom cropping.

“We already had the vision of the way things were going,” says Meinholz, De Forest, WI, whose manure is spread on a total of 6,000 acres of corn, soybeans, alfalfa and other crops.

The new P-based standard means he can apply less total manure on each field. And it's likely Meinholz will end up having to buy commercial N because hitting the P limit with manure nutrients will leave his N needs short.

To meet stiff new regulations, a growing number of livestock producers like Meinholz are on the prowl for land and producers to take the excess nutrients. The movement is taking place throughout corn and soybean country, as states either have already or are in the process of converting from an N-based to a P-based system.

One result is that from now on, crop and livestock producers are going to work closer together, and the timing couldn't be better for crop growers. With “projections and whispers for the next year suggesting anhydrous prices approaching $520/ton, and possibly higher,” livestock producers will find crop growers very interested in “natural” fertilizers, says Robert Mullen, Ohio State University soil scientist. The increase alone in N costs from 2004 to estimated 2006 costs is $13/acre, and phosphorus and potassium costs are rising as well, he says.

Mullen foresees a growing number of arrangements in which livestock producers provide manure-based fertilizers to crop producers who, in turn, provide feed for livestock operators.

There is nothing new about applying manure on fields, of course. But what is changing are regulations. Producers nationwide have historically applied manure based on the N needs of fields, which meant that fields were often over applied with P, experts say. But now that producers can no longer do that, many will have to cut back on the amount of manure that can be applied per acre.

The exception will be the fields low in P or fields that do not exceed a P threshold. Crucial here will be soil testing.

Rules will vary by state, however. Even though shifting from an N-based system to P-based will require more corn acres, there's no danger of running low on land. In Illinois, for example, only 3% of cornfields are currently spread with manure, explains Ted Funk, University of Illinois agricultural engineer.

One issue that will affect both crop and livestock producers is how a crucial federal lawsuit is resolved, Funk says. Earlier this year, a federal district court blocked the Environmental Protection Agency (EPA) from implementing its new Confined Animal Feeding Operation (CAFO) regulations that required livestock operations with greater than 1,000 animal units (2,500 pigs, 700 dairy cows, or 1,000 beef feeders) to have a nutrient management plan, including how the manure is to be applied on fields.

The court found that the rules were discriminatory, and one possible outcome, Funk says, is that the court may require EPA to come up with a plan that requires all livestock producers who are proven to have a discharge, regardless of size, to have a P-based nutrient management plan. The result could be that many smaller producers will be looking for a land base on which to spread manure from their livestock enterprises.

EPA's philosophy, Funk says, was to target the large facilities, which generate about 80% of the manure and thus were presumed to represent the greatest threat to the environment. But in reality, more discharges probably come from smaller units.

But the devil is in the details. The same general rules apply to most states, although when it gets down to specifics, “producers need to be aware that rules differ state by state,” notes Angie Rieck-Hinz, Iowa State University agronomist.

All open feedlots in Iowa that are CAFOs will be required to have a nutrient management plan in 2006. Part of the plan will include a phosphorus index, or risk assessment of the loss of phosphorus from a field. If the phosphorus index is high, producers will not be allowed to apply manure. And the closer producers are to a waterway, the higher the index will be.

In Iowa, if crop growers are using manure from a livestock producer with a confinement operation, the crop grower must file a statement of intent indicating if and how much commercial fertilizer will be applied. In other words, both producers must agree to fertilizer rates. “There needs to be a frank discussion about rates and where it's to be applied,” Rieck-Hinz says.

What's behind the shift from N-based to phosphorus-based rules is concern that P feeds algae blooms in lakes and streams, which settle to the bottom of water bodies and reduce the oxygen levels of the water. Ultimately, this eliminates the ability of fish to live in the water, says University of Wisconsin nutrient management specialist Kevin Erb, in Green Bay.

Wisconsin is in the process of shifting from an N-based to a P-based system. Wisconsin's producers will have a choice of using either the Phosphorus Index or a soil test based system, but both approaches will require that soil erosion be kept below a state-mandated level.

One result of Wisconsin's system will be less starter fertilizer used, Erb believes, but more broadcast fertilizer and more urea used. For those using livestock manure, he thinks the rates will have to be cut from about 12,000 to 13,000 gal./acre to 7,000 to 8,000 gal. on many fields because of switching from N- to P-based rules.

Will switching to P-based rules hurt yields? Erb doesn't think so because many producers have been over-applying fertilizer for years. So, there's plenty of banked P available in soils and producers can supplement N.

In Minnesota, the issue of manure application gets down to two issues: the phosphorus index and the University of Minnesota's recommended application rates. So fields with low phosphorus indices would still be allowed to apply manure based on an N basis, says University of Minnesota Extension specialist Kevin Blanchet.

Minnesota is now in the process of converting to a computer-based phosphorus index guideline formula, as are some other Midwestern states, Blanchet says.

So what do producers think of the new rules? Meinholz says they make some sense, although there's a paperwork burden by having to keep detailed logbooks field by field of how much fertilizer is applied. But he doesn't like the idea that “manure is treated as a toxic waste rather than the sustainable resource that it is,” while commercial fertilizers are not.

In time, though, experts think commercial fertilizers probably will have to meet the same standards that manure now does — a requirement European farmers are now forced to meet. But so far, experts say those rules are at least a decade away.