A heavy fog blanketed much of Ohio one early March morning as the long winter freeze was just starting to give way to the warmer temperatures of the coming spring. A thin top layer of the soil had thawed, but a deep freeze remained below. This, combined with persistent rains and a significant snowmelt, set the stage for nutrient and sediment loss from farm fields.
The Duling Farm in Putnam County has spent generations preparing the fields to withstand exactly these kinds of challenging situations with long term no-till, cover crops, closely scrutinized manure management, meticulous soil testing and analysis of results, injection of nutrients into fields with living crops, buffer strips, waterways, gypsum use, drainage management structures, and other practices to minimize soil and nutrient loss. If it can protect the soil and reduce nutrient loss, the Dulings have probably tried it.
Nonetheless, the thick fog that hung in the air on that murky March morning was not enough to obscure the flow of water containing some soil sediment and nutrients through the cover cropped fields, destined for the nearest waterway and a trip north to Lake Erie.
“Mother Nature still rules. You can’t beat her. I don’t know what else I can do to stop it,” said Jeff Duling. “The field hasn’t been tilled for years and it was in a red clover cover crop. The water was picking up that thin layer of soil that wasn’t frozen.”
The week prior, Duling quietly sat in the back of the room at the Conservation Tillage and Technology Conference in Ada and listened intently to speaker after speaker share the water quality improvement gospel. Based on the practices he has implemented, Duling has it covered when it comes to water quality, yet he knows for a fact that he still has not eliminated soil and nutrient loss from his farm that is contributing the growth of harmful algal blooms in Lake Erie.
“I don’t think this problem is solvable with agriculture. There are too many other factors contributing to this,” he said. “There are septic systems that are shot and people are fertilizing their lawns all over the place. I feel like I am already doing everything I can possibly do. Everybody is on the hunt, but nobody is giving us that golden nugget. You just ain’t going to beat Mother Nature.”
Yet, at the same meeting in Ada, a panel of some of the very best minds working on this challenging issue agreed that the problem of harmful algal blooms in Lake Erie and other bodies of water could be solved with agricultural efforts in front of the crowd of both skeptics and believers. The science and the data being gathered on this issue opens the door for hope that agriculture can bear the burden alone; the cold in-field realities of a foggy March morning, though, provide a healthy dose of doubt.
Few have more thoughtfully and thoroughly assessed this challenge from an agricultural and scientific standpoint than Kevin Elder, with the Ohio Department of Agriculture. He also farms in Fairfield and Perry counties.
Elder pointed out at the Ada meeting that great strides have been made in agriculture for reducing total phosphorus loss through tremendous increases in conservation tillage and nutrient management from the surface of the soil. The problem with the comparatively small losses of dissolved phosphorus now being blamed for the harmful algal blooms, however, needs to be addressed below the surface.
“We haven’t been unsuccessful. We have made progress and that sediment reduction has made a difference in the Maumee River. We have decreased total phosphorus loss and sediment loss, but dissolved phosphorus levels have increased since the mid 90s and have doubled in the last 15 to 20 years,” Elder said. “We’ve had 60 years of research on sediment, with dissolved phosphorous, not so much. With dissolved phosphorus, we are talking about needing only two to four pounds per acre loss on average and you can’t see that. It is less than 5% of the use of a crop. I do not like to have things mandated by the legislature. Some of that may be good, but the ability to use agronomics and commonsense is a lot better.”
Proper soil testing, and the subsequent interpretation of the results, is an important step in the process of combating dissolved reactive phosphorus losses.
“Start with a soil test and understand how to interpret them. Consider more intense testing by soil type with grid mapping,” Elder said. “What is a high soil test? If it is at or higher than Bray P1 over 50 parts per million or Mehlich-3 over 70 parts per million, do not add phosphorus.”
There are a number of other ways farmers can take steps to improve water quality.
“Understand that not everyone can do everything, they don’t need to,” Elder said. “It has to fit your soils, management and operation. It is important to note that zero is not the goal. Water will always flow downhill. We need to commend those who are already doing these things and work on the situations where things are not so good.”
With this in mind, additional suggestions from Elder include:
• Do not apply nutrients on frozen or snow-covered ground.
• Put nutrients below the surface and get them closer to the seed.
• Band more phosphorus two-by-two with the planter.
• Do strip fertilization and come back and plant.
• If you surface apply phosphorus, limit rates to only what crop rotation requires based on soil test and time any broadcast applications to match tillage. Even chisel plowing only mixes the nutrients a third as deep as the depth you are chiseling.
• Look closely at the soil moisture and watch the weather. Incorporate it as quickly as possible to get it out of that rainfall path. Keep records.
• Water control structures should be considered. Those are not suitable for all places and if you put them in, be prepared to manage them. They can reduce nutrient losses and improve yields.
• Put filter strips and buffers where they make sense. Consider harvesting vegetation off of that buffer to keep it active. They get saturated with nutrients and don’t do any good. Keep or plant new riparian areas where possible.
• If there are enough cover crops in a watershed, they can reduce peak flows and keep water for the crop. Water holding capacity is critical. If you can increase your water holding capacity you may not need a drainage control structure.
• Consider increasing organic matter in the soil. Every 1% of OM you add is an inch of water holding capacity.
• Reduce compaction with timely field activity and controlled traffic.
• Denitrifying bioreactors can be used with water control structures to filter nutrients.
• Replace surface tile risers with blind inlets.
• Wetlands don’t fit everywhere, but in the right place they can be very effective for reducing sediment loss.
• Consider nitrogen additives for preventing loss. Calculate available residual nitrogen and variable rates. Thinking about the N application methods is critical.
• Don’t wait, there are always things to be done to improve.
These are all ways to address the complete range of nutrient loss both above and below the ground, which is a crucial strategy moving forward, according to Kevin King, with USDA’s Agricultural Research Service in Columbus.
“We cannot ignore tile drainage. It is a primary player in the amount of phosphorus that is moving out of the ag systems. The recommendations that I make are disconnecting the hydrologic pathways — so putting drainage water management structures in place to disrupt those pathways and keep that water back in the field,” King said. “We also need to make sure we adhere to soil test phosphorus levels. Too many times we are putting way to much phosphorus in these field where we don’t need it — on the surface. If we base application rates on soil tests in the two- to eight-inch range rather than the zero- to eight-inch range, it may have a large impact. Then we need to think about subsurface placement of those nutrients. That is not saying we need to till that in necessarily. We can do that in a no-till fashion. But get those nutrients down three or four inches deep and that will go a long way in reducing what we see coming off the sites.”
Widespread adoption of these practices can significantly reduce loss of dissolved nutrients through tile lines and can make dramatic improvements in water quality, King said. But there is still much to learn.
“We can start to get an idea of what is out there. This is not absolute. We are in our infancy of collecting data,” he said. “If we use the suggested target rates for dissolved phosphorus and average that over the cropland in the Maumee, each producer would be allowed a quarter of a pound per acre of phosphorus coming off of their fields. Some farms are below that and some are well above that, so not every site is going to be the same. From a total phosphorus standpoint we are doing pretty well, but drainage water management has significant potential to reduce the losses of dissolved reactive phosphorus. The solution is the interface between science and implementation. How do we make sure the best science is properly implemented in the field?”
That is a challenge because the science is not quite there yet. Cover crops, for example, have been proven to do a number of positive things in the soil, but may contribute to the problem of loss of dissolved reactive phosphorus.
“Cover crops are great and I believe they are directionally correct, but I think we need to be careful. They can increase infiltration and improve soil health, but if reducing dissolved phosphorus is the primary goal they may not be the best solution,” King said. “For example, the phosphorus concentrations around radishes are much higher in he soil. Then when they die you have a macro pore in the soil going down toward the tile line with enriched phosphorus. We need to be aware of the tradeoffs and make our cover crop selections based on the best science.”
At the same time, though, Jennifer Tank with the University of Notre Dame is doing work with cover crops in Indiana and found a 30% decline in nitrogen loss and a 50% reduction in dissolved phosphorus loss with the use of cover crops.
As farmers consider implementing some or all of these practices on their ground in the coming years, it may be worth targeting specific problem areas of the farm with practices designed to address the unique challenges.
“There are critical zones for phosphorus management that have high potential for transport,” said Andrew Sharpley, a soil scientist with the University of Arkansas. “We often see 80% of phosphorus loss coming from 20% of land area. Target these areas where, in many cases, the right rate for phosphorus is zero.”
These most problematic parts of a farm can be identified by soil test phosphorus levels and the potential to lose soil and nutrients. Areas of field with high levels of legacy phosphorus in the soil, old pastures for example, should be considered a priority for increased management.
“Factors for high transports include runoff, erosion, and flooding frequency,” Sharpley said. “We need to start treating environmental health like we are treating human health. You need to get the diagnosis right first by assessing each case individually and aim for overall improved health. Then we need to get the treatment right and make sure the remedy works. Consider all the benefits and risks, then tweak the system as you go along and learn more.”
In addition to all of the other discussion, gypsum use was also mentioned at the Conservation Tillage and Technology Conference as a potential component to the solution to tie up soil phosphorus by addressing low sulfur levels in the soil.
“Seldom is there a major change implemented when there are not unintended consequences. We eliminated acid rain. That is the good news, but now we have created rainfall with a mobilizing effect. Rainfall used to have an immobilizing effect with acid rain,” said Joe Nester, with Nester Consulting. “Phosphorus is a lot more mobile nutrient than we were dealing with 20 years ago.”
Nester stressed that gypsum has the potential to help keep phosphorus in the fields in the right situations.
“No-till soybean stubble on Hoytville type soils might be a really good place to look at using gypsum,” he said.
Needless to say, there was plenty for everyone to think about with regard to water quality after the two-day event in Ada. There is no doubt that improving water quality is a complex problem that agriculture needs to play an important role in addressing. The details of implementing the right solutions on individual farms may be as clear as a foggy March morning, but everyone can agree on one very simply complex answer as to what needs to be done by Ohio agriculture to clean up the water: more.