Can Mixed Cover Crops Double as a Weed Control and Soil Health Builder?

Contributed by Doug Finkelnburg, University of Idaho

Driving a hundred miles on icy roads for a presentation sparks some interesting thoughts. “Why am I doing this?” crossed my mind more than once, alongside musings that surely, this was what teleconferencing was made for. But as the miles rolled by, a deeper question emerged: Are we approaching cover crops and weed control from the wrong angle?

Cover cropping, with its myriad benefits, is no stranger to those of us navigating the unique challenges of the moisture-limited, wheat-dominant cropping systems of the Pacific Northwest. Our Mediterranean climate throws a wrench in strategies that work elsewhere, like planting cover crops post-summer harvest. By the time we get enough moisture, we’re running low on the heat needed to grow anything substantial before winter sets in. And let’s not even start on the dilemma of spring planting—taking a field out of production for a season is a tough sell without clear benefits, like water banking in summer fallow.

The adoption of cover crops, especially those multi-species mixes lauded by enthusiasts for supercharging soil biology, faces significant hurdles here. Between residual herbicides nixing half your species and the absence of in-crop herbicide options, weed control reverts to the hope that your cover crop can outcompete the weeds through sheer growth.

But what if there was a way to mesh the worlds of mixed-species cover crops and in-crop weed management? As I pondered over whether my rear axle had enough bags of sand for adequate traction, an idea took shape. What about leveraging our RoundUp Ready and Clearfield systems? These systems allow for the use of herbicides within the crop, offering a strategic advantage in integrated weed management. Imagine a spring-planted mix of RoundUp Ready canola, sugarbeet, alfalfa, and corn, with the option of a glyphosate sweep to keep weeds at bay. Or a Clearfield concoction of sunflower, lentil, corn, and canola, allowing for a timely Beyond application while championing soil health.

As an oncoming semi-truck veered a tad too close for comfort, my thoughts took a pragmatic turn. What about the aftermath? Multi-species mixes bring the challenge of varied maturation times, magnified by field heterogeneity. Soil depth, moisture—every variable affects crop maturity, raising the specter of herbicide-resistant plants seeding out before the grand finale of crop termination.

Embarking on this mixed cover crop venture demands meticulous planning, especially in managing termination to prevent any “escapees.” It’s an intriguing concept, ripe with potential yet bristling with challenges. Can we navigate these complexities to harness the dual power of cover crops for both soil health and weed control? The road ahead is as uncertain as a winter drive through the Pacific Northwest, but perhaps, just perhaps, it’s a journey worth embarking on.