New soil test technology could improve water quality and boost profits

By now, there is probably no one left in Ohio who is not at least somewhat aware of the important relationship between nutrient management and water quality — excess nutrients in fields lead to excess nutrients in water. The trick, of course, is knowing the amount of nutrients actually needed in the soil to maximize crop profitability.

This perennially vexing question has been the subject of recent research by the USDA’s Agricultural Research Service at the Grassland, Soil and Water research Laboratory in Temple, Texas. Rick Haney is an ARS soil scientist at the facility and he visited Ohio this spring to share with farmers the innovative changes in soil testing that he has been working with recently to benefit both water quality and farm profitability.

The research combines the old and the new when it comes to soil testing.

“We’re going kind of old school on some of it. We are extracting the soil with water because that is what the soil actually sees out in the field. Then we’re doing a microbial respiration test that we haven’t really had the ability to do before. We’re looking at organic nitrogen compounds out of soil from the water extract that we weren’t able to see before, but we can see it now because of the technology,” Haney said. “We’re using a more integrated approach to try to understand what is happening in these systems. Instead of trying to figure out a whole lot of things from one thing, we’re using a whole lot of things to figure out one thing. Since we are looking at the organic nitrogen compounds in the soil as a whole, we’re seeing $15 to $20 per acre savings in nitrogen.”

With the new soil testing methods, Haney can get a more accurate handle on how much nitrogen is actually available to plants.

“We haven’t been able to account for it before because we haven’t been able to see it,” Haney said. “Since we haven’t seen the water extractable organic nitrogen pool before, we are shocked at what we are finding, especially if you have been applying poultry litter or manure. We see this huge shift from inorganic nitrogen to organic nitrogen pool and that is really important. We’re starting to understand why manure supplies nutrients for years instead of just one growing season. That pool is four times bigger than we thought it would be. “

The per acre savings in nitrogen use have clear environmental benefits, but they also have significant economic benefits.

“Even if it is saving just $5 or $6 an acre, if you are farming 1,000 acres, that is a significant amount of money,” Haney said. “We’re trying to help you get as much out of nature as you can and then supplement the rest you need. We need to accurately measure what is there begin with because that is better for everything.”

In one of Haney’s recent studies, three fertilizer rate treatments were evaluated: no fertilizer (control), traditional rate, and reduced rate based on his enhanced soil testing method at nine sites in Texas. At each location, fertilizer data (formulation, rate, cost, and application date) and crop data for wheat, corn, oats, and grain sorghum (yield, price, and harvest date) were recorded, and the net profit for each crop was determined. In the four-year study, fertilizer rates were reduced 30% to 50% and fertilizer costs were reduced 23% to 39% based on enhanced soil test method recommendations, but yields were not significantly reduced (0-6%). The oat yields actually increased 5%.

The profitability decreased less than 1% for corn and increased 7% to 18% for wheat, oats, and grain sorghum with reduced fertilizer rates.

“Although these changes were not significant, they do represent potential benefit through increased profit and decreased input cost and production risk,” Haney said. “In only 6% of the time was the traditional fertilizer rate the most profitable, compared to 51% for the unfertilized treatment and for the 43% for the enhanced soil test treatment. These results do not indicate that fertilizer application should be avoided, but that fertilizer rates should be carefully chosen considering all sources of plant available nutrients to ensure that fertilizer is applied at the optimal rate.”

Haney is looking to expand his research into other areas, including Ohio.

A PowerPoint presentation from Haney is available at

ftp://ftp-fc.sc.egov.usda.gov/ID/technical/rick_haney_soil_chemistry2.pdf. To learn more, contact him at 254-770-6503 or rick.haney@ars.usda.gov.

 

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