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What does the future hold for nutrient management practices?

Progressive Dairyman Editor Karen Lee Published on 09 January 2018

Not a single speaker at the University of Wisconsin Discovery Farms Conference claimed to be in possession of a crystal ball, but that didn’t stop them from hypothesizing about what might be next in terms of nutrient applications. Looking to the future is important because today’s best still isn’t good enough.

“Implementing current best practices is not enough. We will not achieve water quality goals if you do everything right,” Dr. Josh McGrath said.

“That’s a bitter pill to swallow, and I think we’ve denied it for too long. We need to do everything right, I’m not arguing against that, but I’m saying we need to do more,” he continued.

McGrath, an associate professor and soil management specialist, University of Kentucky, opened the Dec. 12 conference in Wisconsin Dells, Wisconsin, by explaining how maximum yield, maximum profit and environmental protection are competing interests when it comes to nitrogen application in corn.

“At the beginning of the season, we have difficulty predicting the nitrogen rate that is going to be most profitable, highest yielding or protect the environment,” he said. Knowing they are in competition with each other makes the rate selection even more complicated.

Nitrogen requirements are complex. They are based on plant responsiveness, potential yield, amount of nitrogen in the soil, soil type, climate and many other factors. The requirements can change across a field and from season to season.

“Even if you follow the recommendation that’s appropriate for your situation, you’re still leaving a surplus of environmentally risky nitrogen because we can’t precisely predict it right,” he said.

Based on data from Delaware, McGrath reported farmers came in close to meeting recommendations when applying nitrogen, but in really dry or really wet years, a surplus occurred.

These recommendations are accurate because they are based on data sets over many years and many fields. “They are right on average,” he said, “but in every spot, in every year, they are wrong. That’s imprecision.”

McGrath called for new methods to making rate decisions for nitrogen application. Engineers have developed machines that can apply at different rates, and enhancements have been made in soil measurements and yield mapping. These technologies were not around when current recommendations were developed.

Phosphorus is very different than nitrogen. Less than 15 percent of applied phosphorus is available in the first year. Very small portions are lost in runoff, but it can still be well beyond the environmentally critical value. Legacy phosphorus, or the amount held in the soil, can be quite high and a source of contamination as well.

Managing phosphorus requires a long-term focus on balance, McGrath said. Different sites require different answers, as direct injection and no-till don’t work well in every instance.

For better practices in the future, “we need to understand the underlying processes that contribute to nitrogen surplus and phosphorus transport,” he said. “We need to do research in new ways with new tools.”

After pointing out that his smartphone is 4 billion times faster than the computer used to put man on the moon nearly 50 years ago, Dr. Raj Khosla said, “The devices we are working with today are phenomenal, and we are not necessarily taking advantage of what they can do for us.”

Combining devices, data and decisions is the backbone of precision agriculture. For years, farmers have used their eyes, ears and nose. Today, we have sensor technology, and we are storing data on a cloud server.

This professor of precision agriculture at Colorado State University said that in any given year, close to 30 different data layers could be collected for a single field. The question becomes: How do farmers decide which layer is more important than others?

“It will get more complex before it gets easier,” Khosla said. Farmers are using the latest technology with algorithms that don’t match up with what the technology can do.

He backed McGrath’s statement about how averages don’t work well in a world with precision technologies. “When you are chasing the average and the average only exists in 10 percent of the field, you are off target 90 percent of the time,” Khosla said. He cited one example where 40 percent of the field ended up being under-fertilized and 24 percent was over-fertilized.

“It's not only about farming the land, it's also about farming the data,” he said, noting the same yield map can be used to create a profit analysis map. “Your most profitable acres may not be the most productive,” he added.

Finding our way forward in precision technology will be done in small steps, Khosla said.

Amber Radatz, co-director of the University of Wisconsin Discovery Farms, provided several manure management steps farmers could adopt today that may help determine whether or not they have a license to continue farming in the future.

Manure management is not in sync agronomically and environmentally. “You’ve got to find somewhere in the middle,” Radatz said.

She also noted that these steps are suggestions and not endorsements or silver bullets.

The first step is to consider timing. In the Upper Midwest, February and March is a risky time to apply manure due to snowmelt and heavy rains that increase the likelihood of runoff events. Newer techniques – like cover crops and irrigation – can be added to a manure management system and allow manure to be spread when runoff is less likely.

The next step is looking at the placement of nutrients in the soil. “Nutrients should be placed below the soil surface, but not with so much disturbance that soil loss becomes an issue,” Radatz said.

Rate of application is another step for farmers to watch. “There is no relationship between yield and the amount of nitrogen supplied,” Radatz said. “What we saw in the data was that as nitrogen rates increase, yield does not change.”

She compared nutrient crediting to online shopping, where you order something and then wait for it to arrive. If the item you ordered doesn’t arrive on time, you start investigating what may have happened to it along the way. The same goes for nutrient crediting from manure, she said. If you put your manure order out there and it doesn’t arrive, maybe you should investigate why that happened before placing another order.

“Because there is variation in nutrients in manure, doesn't mean you shouldn't credit them,” Radatz said. A better approach is to verify your own situation. Test the nutrient content of the manure and develop realistic yield goals through record keeping and nitrogen use efficiency calculations. Then adjust your nutrient applications and repeat the process every year.

The final step is to consider the final products you have or could have through mechanical separation, treatment or composting. The added benefits for hauling, odor control or nutrient availability could be useful to farmers or the people around them.

Even if the future is unknown and more work needs to be done to adjust current recommendations with new precision technologies, there are steps that farmers can take today to improve manure and nutrient management.  end mark

Karen Lee
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