Field and Garden: Should I be using 'biologicals'?

In 1893, William P. Brooks conducted a classical experiment at the Massachusetts Agriculture Experiment Station.

Brooks filled pots with soil that had never been exposed to soybeans. To one group of pots, he sprinkled a pinch of dust collected from the floor where soybeans had been threshed. The remaining pots were left untouched.

The outcome was remarkable: Soybean plants in pots with added dust were greener, more vigorous, and higher yielding than plants without dust.

Although the mechanism wasn’t fully understood, Brooks’ experiment demonstrated that soil inoculation could dramatically improve soybean growth and yield.

Within the next decade, the USDA launched a program to bolster agricultural production by providing farmers with free inoculants for soybeans. The tradenames of some these products were Farmogerm, Nitro-germ, Radicin and Legume-aid.

Of course, we know now that the improvements that Brooks observed in soybean growth were caused by rhizobia bacteria present in the dust that he sprinkled into the pots.

Residing in nodules on soybean roots, the bacteria extract nitrogen gas from air and convert it into a form that soybean plants can utilize.

Over the decades, scientists have continued searching for naturally occurring substances and microorganisms that enhance crop growth when applied to seeds or plants.

Called “biologicals,” these agents are thought to work in harmony with nature to improve nutrient use efficiency and increase tolerance to environmental stress.

Many biologicals are now on the market. The problem is that we don’t know if they really work.

To address this issue, NDSU scientists recently joined with researchers from other land-grant universities to conduct experiments examining the effects of biological products on crop growth.

In the first study, researchers tested the effects of seven biologicals on corn, wheat, canola and sugar beets in ten north central states, including four sites in North Dakota. Biologicals increased yield in just two of 61 trials.

The second study examined the effect of biological seed treatments on soybean yield and profit at 25 locations around the U.S. Two trials were conducted in North Dakota. The biologicals had no significant effect on soybean yield either in 2022 or in 2023.

More research will be done in the future, and new products are certain to come on the market.

For now, NDSU Extension soil scientist Dave Franzen urges caution. He recommends that farmers conduct strip trials on parts of their farm before purchasing new products to use on all their land.

Franzen also points out that millions of naturally occurring microorganisms are already present in soil, actively engaged in organic matter decomposition and nutrient cycling. He advises farmers to work towards harnessing the power of these native microorganisms.

The adoption of no-till practices can help. No-till creates a soil environment that promotes microbial activity and the release of nitrogen from organic matter.

Research indicates that farmers with continuous no-till fields need 40 to 50 pounds less nitrogen per acre to grow corn than farmers with conventionally tilled fields.