Renewable Farming

Turkeys in the driveway

More crop diversity, fewer crop pests

Finally, researchers have actually counted aphids, beetles and other insects in a wide array of actual farm cornfields to confirm — statistically — what many agronomists have long observed:

Wider crop diversity on a farm increases diversity of arthropods and thus reduces economic losses from runaway populations of damaging insect pests.

Amazingly, USDA-ARS entomologist Jonathan Lundgren and South Dakota State University economist Scott Fausti actually counted 37,185 arthropods (insects and spiders) of 106 types on 53 cornfields widely distributed across South Dakota. The diversity surrounding these farms varied widely. Using careful statistical measures in a two-year project, the researchers analyzed the impact of crop diversity on these farms in terms of insect pressure and variety.

Their research report, linked below, is written in scientific terms. But the bottom line is this: As diversity increased in crops surrounding the cornfields studied, pressure fom damaging pests such as aphids and beetles decreased. A wide range of crops and plants increased the range of competing insect species, and the competing species prevented runaway outbreaks of economically damaging insects.

The scientific summary of the research report puts it this way: “Our results show that increased species diversity, community evenness, and linkage strength and network centrality within a biological network all correlate with significantly reduced pest populations. This supports the assertion that reduced biological complexity on farms is associated with increased pest populations and provides a further justification for diversification of agroecosystems to improve the profitability, safety, and sustainability of food production systems.”

The authors point to the economic benefit of their study with this observation: “Our research suggests that agronomic practices that promote high levels of arthropod diversity fundamentally require fewer agronomic inputs.”

They suggest management practices to increase biodiversity such as lengthening crop rotations, including cover crops in rotations, intercropping, managing field margins and developing minimal-till organic agriculture.

You can read the entire study as a PDF (portable document file) at this link.

Their study is the first statistical analysis we’ve seen which confirms many “Renewable Farming” consultants’ observations. Dave Larson, founder of AgriEnergy Resources, maintained that one of the most important measures of “fertility” was the widest possible spectrum of species in the soil food web. That included microbes, micorrhizae, earthworms and the entire range of insects and spiders (arthropods). 

More recently, retired USDA-ARS soil scientist Dr. Robert Kremer reminded farmers at a December 2014 seminar in Overland Park, KS that adding cover crops or more diverse rotations to a corn-soybean program rapidly amplifies the diversity of soil microbes.

We’ve found that on our own research farm. This season we planted corn, soybeans, sweet corn, spring wheat, grain sorghum, sunflowers and proso millet. After the wheat and sweetcorn, we’re planting tillage radish blended with red clover as a cover crop.

We’ve never used glyphosate or insecticides. Since 1972, we’ve also planted a wide array of trees. Now, as the only non-GMO and diverse farm for many miles, our place looks somewhat like a wildlife reserve. We have a herd of resident deer, dozens of bird species and what appears to be a very generous allocation of skunks, possums, rabbits and raccoons. Beaver migrate up and down our creek, occasionally building dams and harvesting entire patches of corn. Muskrats have learned to ignore our tractors as they browse for sweetcorn the raccoons left behind.  This afternoon when we drilled tillage radish and clover into wheat stubble, a flock of about 200 doves rose up from the wheat field. 

This season, a flock of 14 wild turkeys has moved in. They’re a bit wary, but brave enough to wander into our back yard, near the chicken house. See photo below.

We haven’t counted the variety of bugs here, but we’d be willing to assure Lundgren and Fausti that we probably have a wide diversity out here. We’ve not seen a single aphid on our soybeans until this week. This evening, there are just a few showing up; one or two on the upper leaves. Rather than insecticide, we will lay down another foliar feeding of trace elements and Seed Set from BRT, “amplified” with WakeUP Summer.

Farmers all around us started spraying aphids with insecticides about a week ago. We’ve seen only a few Japanese beetles. No signs of corn rootworm, either.

Our approach to crop protection is the one documented by John Paull at the Fenner School of Environment and Society, Australian National University, Canberra.  “Pests shun healthy plants. Pesticides weaken plants.”   You can read Paull’s well-documented argument by downloading a PDF summary at this link.


Turkeys in the driveway
Our resident turkey flock likes our crop diversity  Photo by Blake Carlson