Best Phosphorus Management Practice

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On-Field Ohio! project to evaluate/revise the Ohio Phosphorus Risk Index (P Index) 

Farmers have every incentive — economic and environmental — to do what is right with regard to nutrient management and water quality.

The challenge is that no one out there is quite sure what the right things to do really are, at least not yet. This is where the extensive effort of the On-Field Ohio! project to evaluate/revise the Ohio Phosphorus Risk Index (P Index) comes into play.

Identified as the key nutrient in the formation of harmful algal blooms in Lake Erie, Grand Lake St. Marys and other bodies of freshwater, phosphorus is the primary focus of efforts to improve water quality. The P Index takes a broad look at various on-farm management practices and scores them based on the risks and benefits they contribute to improving phosphorus management.

“The Ohio P Index is intended to provide a field scale estimate of phosphorus runoff risk. It is based on field physical characteristics as well as farmer management practices,” said Elizabeth Dayton, a soil scientist with the Ohio State University School of Environment and Natural Resources who leads the project. “The P index concept has been around since 1993. The P Index considers risk factors for phosphorus transport that affect runoff like slope, infiltration rates and risk factors for phosphorus sources such as tillage, fertilizer placement method and soil test P.

“It all started with the creation of the P Index framework in 1993 where USDA-NRCS in collaboration with Land Grant universities developed state P indices. Since then, there has been a revised Nutrient Management Standard from USDA-NRCS that puts a big emphasis on validating/updating state P indices. Luckily, just as that new standard was released, we were putting this project together so we are very much in line with what needs to be accomplished moving forward.”

Since its creation, the P Index has been offering farmers insights into the decisions they make with regard to the phosphorus management on their farms with a scoring system for management practices. The problem is that the Ohio P Index has never been validated for accuracy with on-farm tests to see if the system reflects P runoff risk from farm fields.

“Ohio’s P risk index had never been validated. If we don’t have an accurate assessment of the risk then we don’t know if the index is functioning correctly,” Dayton said. “There has been a lot of small plot work nationally and states borrow from each other, but we really hadn’t done much field work in Ohio, so that is why we are doing this. We aren’t the only state looking to revise their P index. Ohio is really joining the conversation on this with the work we are doing now.”

More than $1 million has been invested in On-Field Ohio! by Ohio agricultural organizations, including the Ohio Soybean Council, Ohio Corn and Wheat Growers Association and the Ohio Small Grains Marketing Program. This major investment is being used for conducting on-farm, edge-of-field testing through a partnership with The Ohio State University, OSU Extension and the U.S. Department of Agriculture’s (USDA) Agricultural Research Service. The USDA-NRCS matched the $1 million investment, creating a total of $2 million for the on-farm research.

“The sampling equipment alone is $1 million and it costs $500,000 a year to collect the samples,” Dayton said. “Our research relates the field management practices and the soil chemistry to the field runoff. This will allow us to help farmers make management decisions to go along with what they already know about their agronomics.”

The help of agricultural commodity groups got the process started, but it would not have continued without the cooperation of farmers throughout the state. After the funding was in place, the next step was to find the fields that would most closely meet the project’s parameters and then get permission from the producers of those fields to set up the necessary equipment, which includes a station for surface runoff and a station for tile runoff.

After runoff water is collected at each station, the samples are taken to the lab and analyzed for phosphorus, nitrogen and sediment content.

“Thanks to Greg LaBarge, OSU Extension field specialist, we collect a tremendous amount of information about farmer management to compare to the runoff so we can relate the on-field practices and storm events with what we see in the runoff,” Dayton said. “That is what is helping us to revise the P index.”

Terry McClure’s farm in Paulding County is one of the research sites for the project. McClure is very comfortable with the process now that the stations are in place, but admits it took some consideration before putting his farm and farming practices under a microscope.

“You try and think about all of the ramifications of being involved in a project like this,” McClure said. “I worried a bit and then thought to myself that this needs to be done. We don’t know what is causing the issues in Ohio and agriculture needs to be one of the first ones to know. If some of this run-off is coming off of my farm, I need know how and what we can do to change that. That is lost nutrients for farmers and we need to understand it.”

McClure hopes this research will help many farmers in his area and hopes that he can benefit firsthand from having this research station on his farm. He wants to be sure he is applying the nutrient at the right time, doing the best job with the right amount, and going through the rest of the 4R thought process at a very local level.

“Let’s face it, we all have a system that we get in to,” McClure said. “Is my system the best? Can I make small adjustments to apply the nutrient that is needed to make better use of it and make sure I keep it on the soil when it belongs?”

The research is now being conducted on 29 farm fields around Ohio with 15 different farmers.

“We have 14 fields in the Western Lake Erie Basin and eight in Grand Lake St. Marys watershed and seven in Scioto River Watershed,” Dayton said. “We really appreciate our participating farmers. They just farm the fields as they had been doing. We have a broad range of farmer management practices represented. Some of our farmers use long-term no-till and some of our farmers are using lots of tillage. We have surface broadcast, banding, and combinations represented in our farms. We interviewed them ahead so that would be built into the study. This wouldn’t be possible without their help and the support we have received from Ohio agriculture. Ohio ag is really committed to being a part of the solution here.”

So far, data has been collected on more than 1,000 runoff events generating more than 8,000 runoff water samples with more than 24,000 analyses completed. More than 1,500 soil samples have been taken resulting in more than 6,000 soil analyses.

“Our first year was really consumed with just doing the sampler installation and we still don’t even have a full crop rotation for some of our participating farmers. If we really want to see the results of some of these practices we need more opportunities to see some working,” she said. “We are looking at the resiliency of these practices to these big rainfall events. We’re in our third year of collecting data. It was initially a three-year project and we just put in a request for a three-year extension.”

Moving forward, the key objectives of the research are to begin to summarize the vast amount of information to:

  1. Evaluate the Ohio P Index so that the scores accurately reflect transport runoff risk.
  2. Increase the number of management options integrated into the Ohio P Index for fields with high scores.
  3. Implement the revised P Index on a broad scale to protect Ohio surface water quality.
  4. Create a Web-based tool so farmers can easily calculate and manage their transport runoff risk.

Source: OCJ

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