Illinois is conducting a project to resample soil from 450 privately owned farmland sites, where soil was sampled over 120 years ago, in an effort to understand how soil has changed over time. Some of the phosphorus that was put down as rock phosphate in the 1910s may still be present, which could be a resource for crops and can be mined. Soil samples from Illinois counties taken beginning in 1899 have been archived, and researchers are using them to resample locations to measure stock changes. The project will provide new insights into soil fertility management and conservation, leading to updates in the Illinois Agronomy Handbook. Researchers have also repatriated soils from Nebraska, which weren’t being kept at U of I beginning in 1950, and this adds to the longevity of the chronosequence time series.
University of Illinois Leads Statewide Project to Resample Soil from Original Sites
The University of Illinois and its partners have launched a statewide initiative to study soil phosphorus levels and changes in the past 120 years. The project, led by Andrew Margenot, an assistant professor at the university, aims to resample soil at 450 privately owned farmland sites across Illinois that were initially sampled more than a century ago. The researchers intend to contact landowners and farmers to request permission to collect soil samples for the project. The goal of the resampling is to understand how soil has changed over time.
“Our predecessors had the foresight to keep records of soil sampling locations and to store those samples at the university,” said Margenot. “By resampling soil from these same locations, we will gain unprecedented insight on how these soils have changed over 120 years.”
This project is funded by the Illinois Nutrient Research and Education Council (NREC), with additional funding from partners such as the Illinois Farm Bureau and Illinois Soybean Association. The NREC fund has helped to attract over $2.5 million in federal funding, including a $2.2 million National Science Foundation (NSF) grant.
The findings of this project will provide new insights into soil fertility management and conservation, leading to updates in the Illinois Agronomy Handbook. Farmers and landowners will receive anonymized soil data, and the soil sampling process will have minimal impact on their land. Researchers will use a 1 1/2-inch diameter probe to collect soil samples from a 3-foot depth at three points within a 10- to 15-foot area. The location data will be anonymized at the county level to protect privacy.
Margenot highlighted the project’s significance in terms of legacy phosphorus, which refers to the phosphorus that has built up in soil over the years due to the application of phosphorus fertilizer. The researchers can answer questions about legacy phosphorus with the help of soil archives dating back 120 years. “A lot of this was phosphorus put down in the early days when phosphorus fertilizer became a thing,” he added.
The NREC website contains a map and QR code that show the locations of earlier soil testing. Farmers and landowners can participate in the history of soils in Illinois by providing soil samples for the project. This initiative is expected to provide unique insights into how soil has changed over time and how to manage soil fertility and conservation better.
Illinois Researchers Investigate Legacy Phosphorus in Soil
The University of Illinois and its partners are studying soil phosphorus levels and changes over the past 120 years. Andrew Margenot, an assistant professor at the university, is leading the project, which involves resampling soil from 450 privately owned farmland sites in Illinois. The goal is to understand how soil has changed over time.
“One of the applications of a soil archive that goes back 120 years is that we can answer questions uniquely on legacy phosphorus,” Margenot said. “Legacy phosphorus means phosphorus that has been built up in years past and is agnostic to the duration of that. So, it could have been a year ago, it could have been 100 years ago.”
Legacy P and its implications
Margenot noted that the phosphorus content in the soil is about 12% P205 (phosphorus pentoxide) today, but some of the phosphorus that might have been put down as rock phosphate in the 1910s could still be present. This phosphorus is a resource for crops and can be mined. It does not tend to leach or have a gas phase like nitrogen. Therefore, unlike nitrogen, this phosphorus is still there, which has agronomic implications. However, this enrichment of phosphorus in surface soils might be susceptible to being lost as dissolved reactive phosphorus from the runoff pathway or by leaching by tiles, which has implications for water quality.
Legacy P is difficult to quantify, especially at smaller scales of space and time. However, the archive of soil samples will allow researchers to understand, at scales ranging from state to county and 100-year time scales, what the magnitude of legacy P might be.
The Morrow Plots
Using the Morrow Plots archived soils, researchers have demonstrated that potentially large legacy P magnitudes can accrue in relatively short periods of time. The Morrow Plots on the U of I campus were established in 1876 and are the oldest experimental field in the nation. The plots were sampled in 1904 and the soils from that sample are in the university archives. The cores were analyzed for P stocks up to 3-feet deep, and cores have more recently been sampled from that same location.
Margenot said most of the legacy P that was built up today was built up initially in about 1910 to 1920. During this phase, most rock phosphate was being used, about 3,000 pounds per acre. Researchers found that the surplus in these fertilized plots was roughly 1,400 pounds of P per acre, which is not P205 but P. It was mostly found in the surface – the top 12 inches.
The surplus phosphorus has transformed and repopulated in different pools that vary in their availability and loss risk. There is a bit of soil P depletion at depth, which is getting down to about 3 feet and is a bit unexpected. Therefore, researchers have been mining subsoil P.
County and Statewide Magnitude of Legacy P
U of I researchers Mark David and Lowell Gentry reported their findings in 2000 that in less than three decades, roughly 5 billion pounds of P was applied in Illinois and not removed by the crop harvest. The findings of this project will provide new insights into soil fertility management and conservation, leading to updates in the Illinois Agronomy Handbook. Farmers and landowners will receive anonymized soil data, and the soil sampling process will have minimal impact on their land.
Illinois Soil Found to be Naturally Rich in Phosphorus
Illinois croplands are rich in phosphorus, with about 203 pounds of P per acre across the state, according to Andrew Margenot, assistant professor at the University of Illinois. The state is conducting a project to resample soil from 450 privately owned farmland sites, where soil was sampled over 120 years ago. The goal is to understand how soil has changed over time. Margenot noted that some of the phosphorus that might have been put down as rock phosphate in the 1910s could still be present. This phosphorus is a resource for crops and can be mined.
Soil Archives and State Scale Measurements
Soil samples were taken in each Illinois county beginning in 1899, and those same soils that were sampled beginning in 1899 are still present. These samples have been archived, and researchers are using them to resample locations to measure stock changes.
The project is unique because the resampling is happening at a state level. Margenot said, “We are able to go beyond that mass balance and actually verify the balance at state scale, and that’s where our state is unique, and we have a chance to test the how much and the where of legacy P for the Midwest.”
Repatriating Soils from Nebraska
Researchers have also repatriated soils from Nebraska that weren’t being kept at U of I beginning in 1950. These soil samples add to the longevity of the chronosequence time series.
The project will provide new insights into soil fertility management and conservation, leading to updates in the Illinois Agronomy Handbook. All soil data would be provided to the farmer/landowner, and the soil sampling process will have minimal impact on their land.
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