Microdosing research helps farmers in Africa

A farmer who worked with the team weeds a field near Cotonou, Benin. The researchers took samples of the soil before and after amaranth and solanum crops were planted to analyze the impact of the crops on the soil. This image is from before the crops were planted.  |  University of Saskatchewan photo

A project at the University of Saskatchewan has determined how 
to fertilize at less cost and with greater sustainability

Fertilizer microdosing after plants have emerged is helping farmers in Africa grow more food, save money and help the environment.

It was part of a seven-year research project by researchers at the University of Saskatchewan to help farmers in West Africa’s sub-Sahara region grow vegetables less expensively and more sustainably.

“Instead of broadcasting fertilizers, we combined them with manure and put them in the soil after plants emerged,” said Derek Peak, professor of soil chemistry in the College of Agriculture and Bioresources.

“We found that we could probably take the amount of fertilizer that farmers were using, cut it about a fourth and still double yields compared to what their local practice was,” he said.

U of S researchers along with agronomists in Nigeria and Benin explored the effects of fertilizer microdosing on four popular green vegetables widely eaten and marketed: amaranth, solanum (African eggplant), ocimum (African basil) and telfairia (fluted pumpkin).

Soil conditions included dry savanna and rainforest including the Sudano-Sahelian region in Nigeria.

Normal agriculture practices there involved spreading fertilizer (urea) across the field and irrigating, however irrigation can wash away much of the fertilizer and cause large scale algal growth in bodies of water.

“When you put a lot of urea on a tropical soil, it drops the pH to the point that you start seeing the aluminum toxicity and other problems. To provide enough nutrition for the plants to really grow, you were limiting your yields due to acidity. So by having the manure in that system, it buffered the pH but also complexes the aluminum and lowers its toxicity,” Peak said.

However, when it comes to applying small amounts of fertilizer to soil, a key question is if it is sustainable and if large yields are coming at the expense of long-term soil health.

University of Saskatchewan researcher Derek Peak works at the Canadian Light Source synchrotron, where the team used the SXRMB beam line to analyze their samples. | Canadian Light Source photo

“Are you going to end up mining nutrients or damaging the ecosystem by your activities,” said Peak.

After initial field studies, samples were brought back to the Canadian Light Source at the university to specifically look at the molecular level of how vegetable agriculture was changing the soil organic carbon, nitrogen and phosphorous.

The synchrotron allowed the scientists to quickly identify what was happening to the phosphorus in the soils during the growing season.

In both systems, the addition of nitrogen fertilizer to the soil changed how phosphorus cycled, causing potentially detrimental effects, but each region’s soil had sharply different results overall.

Much of the modelling for the African research is based on the 4R (right source at right rate, right time, right place) nutrient stewardship approach practiced in North America.

“We band apply most of our fertilizer in this part of the world. That more or less was what we were doing in Africa — just a really low-tech version.

“You’re injecting it into the soil. People even band apply manure. So we’ve really moved away from broadcasting and I think that was really one of the big advantages of our project too,” said Peak.

“You get way more performance when you put the fertilizer in the soil where the plant is going to be able to access it and not have it lost to erosion.”

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