High-tech equipment used to evaluate soil fertility
Portable X-ray fluorescence spectrometry is normally a process used by those in the metal industry, but a study funded by the Louisiana Soybean and Grain Research and Promotion Board is using the equipment to look at fertility issues in corn and soybeans.
LSU AgCenter soil specialist Beatrix Haggard is taking samples of young corn and soybean plants as a first step in calibrating this portable equipment to correspond to the equipment in labs on the LSU AgCenter campus in Baton Rouge.
“What we’re doing is looking at how we can get vital information to growers in a matter of minutes that currently can take up to a month,” she said.
This year most of the work will involve gathering data for calibration so she is sure the field results correspond to the lab findings, she said. “This is the first year of what will probably be a four-year study.”
The machine uses X-rays to scan plant samples, and the color of the reflected light indicates the amount of the elements being analyzed.
“Soil scientists have been using this technology for the past 10 years in soil,” Haggard said. “They have been using it for environmental remediation, looking at heavy metals like arsenic and lead in the soil.”
This machine has never been used with plants, she said, but it is commonly used in steel manufacturing to look at impurities in metals like gold and silver.
“Some dried, ground plant samples have been scanned,” she said. “But no fresh, green samples from the field.” This is why this first year of the study will require extensive calibration because it’s never been done before.
“It’s not that we don’t trust the machine,” Haggard said. “We’ve done great correlations with the lab results, but moisture affects those results a lot.”
When plant samples are sent to the lab, they are dried, ground , and then analyzed. This has to be taken into account when analyzing fresh samples in the field because of the moisture differential, she said.
“You get different variations by slight amounts, so all we’re trying to do is correct for that,” she said.
The equipment used in the study is not something that the average farmer will go out and buy because the price is prohibitive, Haggard said.
“At $37,000 per unit, this will more than likely be something that would be used by LSU AgCenter agents and crop consultants,” she said.
The analysis will allow growers to know immediately what may be wrong with plants and what needs to be done to correct the problem.
Haggard said the key to the process is to get the analyses done while the plants are young so fertilizer applications can be made in time to affect yields of the current crop instead of providing information for the next year, as the situation is now.
“This is the first step in this study,” Haggard said. “The second part of the research is looking at a variable-rate application for residual nitrogen across soil types.”
In Louisiana, soil types can change across a single field, so growers need to know how much of each fertilizer nutrient needs to be applied, and where.
In this study, Haggard is using GPS, GIS and other technologies to change application rates on the fly.
“The software determines how much material to apply without the farmer having to make any adjustments,” she said.
The GPS system determines exactly when an application rate needs to change and makes the adjustment automatically.
Haggard said the overall purpose of her research is to help corn and soybean farmers speed up the process for making decisions in order to maintain or improve yields.
She said the portable X-ray fluorescence spectrometry equipment can be used in other crops, but she is focusing on corn and soybeans because they are the two main crops being grown in north Louisiana.