Massri uses a syringe to extract the soil solution.

Testing soil solution to gain insights into the 4Rs

In terms of the Right Rate component of the 4Rs, the folks at AgroLiquid are taking a novel approach to finding it through research and unique method of monitoring the fertility in the liquid between the soil particles.

Using a series of syringes attached to tubing placed at varying depths beneath the soil, the soil solution underground can be carefully extracted. The nutrient levels in the solution can then be compared to nutrient application rates to get a handle on what the plants are using and what is being lost.

“We have developed this method of how to test nutrients in soil solutions to see how much is lost. What we are doing has the potential to change how the industry approaches fertility and the loss of nutrients,” said Nick Bancroft, vice president of AgroLiquid. “We test the nutrient solution to see what nutrients are moving in the soil and compare that to what was applied and see what amount was used and what amount was lost. You can figure the math backwards. This lets us compare products in terms of optimal yield and minimal nutrient loss, which is really what everyone is after.”

This unique soil testing method uses micro-lysimeters made of micro-porous hydrophilic Teflon. This enables an improved suction of soil solution to measure plant usable nutrients

Zouheir Massri, with AgroLiquid, stands with a display that shows how the soil solution sampling method works.
Zouheir Massri, with AgroLiquid, stands with a display that shows how the soil solution sampling method works. dissolved in the soil solution.

To test advantages of using phosphorus encapsulated by Falvonol Polymer Technology preventing fixation with soil cations, for example, hydrophilic lysimeters were installed horizontally in solid soil at 10 centimeters and 20 centimeters beneath soil surface (below the corn seed and phosphorus placed in furrow at five centimeters deep). The lysimeters were connected to a transparent PVC tube at the soil surface and extended with a flexible piece of PVC tubing for easy connection-disconnection with 30-milliliter vacuum polycarbonate syringes for suction of the soil solution and measurement of dissolved phosphorus, said Zouheir Massri, who leads the research effort for AgroLiquid. “Knowledge of ion exchange in soils would predict that anions are not retained by the negative charged soil colloids, and move in the soil similar to nitrogen. But phosphorus moves very little, or is relatively immobile in the soil compared to nitrogen and is not lost into the atmosphere. Rarely does it leach beyond the reach of roots, even with large amounts of precipitation or irrigation. This apparent anomaly is that the soil solution contains only a very small amount of available phosphorus in ionic forms at any one time, knowing that the soil solution levels for phosphorus are considered critical for plant growth. That is important because crops take up phosphorus only from the soil solution, and was the core of our testing method to measure the soil solution content of dissolved phosphorus by lysimeters solution suction.”

AgroLiquid is also using unique methods for nitrogen research work. Because nitrogen can be lost through both volatilization and leaching, two tests are conducted for nitrogen loss. There is one for assessment of the nutrients that flow in soil with lysimeters and the other is for ammonia volatilization in the atmosphere. To test volatilization, passive samplers are filled with 20 milliliters of a diluted sulfuric acid and placed in the center of each treatment to trap the ammonia as “ammonia collectors.”

“The solution of the ammonia collectors in the passive samplers continuously absorbs ammonia, and is replaced regularly depending on the expected intensity of the emissions,” Massri said. “The principle underlying this method is that the passive samplers placed in a homogeneous experimental field…have the same NH3 absorption behavior under identical environmental conditions.”

The passive sampler method was developed in the 1970s and proven valid under a wide range of experimental conditions and is recommended to be used under conditions with bare and/or cultivated soils.

Ultimately, the ongoing research at AgroLiquid is showing that the right rate can be significantly lower while maintaining crop productivity if the other three Rs are correct.

“From the beginning we created products that were more effective per pound applied, which allowed growers to apply less total nutrient. It also allows for placement closer to where the plant is going to utilize the nutrients, which prevents offsite nutrients. It allows us to use the right rate and right formulation. at a low rate. It is the right source because it allows you to do the other three Rs,” Bancroft said. “The industry reaction as a whole has been to try and use the products they have always been using. I think it is our responsibility moving forward in educating people that they can get away with reduced rate fertility if they are using the 4Rs.”


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