Biomass Thresholds for Cereal Rye Cover Crop Goals

Abstract

Cover crops can provide a wide range of benefits in dairy and grain production systems, but no single cover crop species or management approach can deliver every benefit at once. One of the keys to making cover crops successful is starting with a clear goal. Common goals include:

scavenging nitrogen that might otherwise leach away reducing erosion and nutrient runoff suppressing troublesome weeds Once a goal is established, choose the cover crop species best suited to achieve it. Equally important is managing the cover crop so it has the time and conditions needed to deliver on its purpose without compromising the cash crop. A clear goal minimizes risk, helps measure success, and keeps expectations realistic.

Other goals, like building soil health or promoting beneficial insects, are also valuable. However, they tend to develop more gradually and are harder to directly measure on an annual basis. That said, goals like erosion control, nitrogen scavenging, and weed suppression often contribute to long-term improvements in soil health and promote beneficial insects, even if those aren’t the primary targets.

Ultimately, the effectiveness of a cover crop depends on one critical factor: the amount of biomass it produces (1). The biomass required is different depending on the goal for the cover crop. What’s adequate for erosion control may not be enough for weed suppression. It’s also essential to consider the trade-offs between increasing cover crop biomass and managing the cash crop.

To help farmers set realistic biomass targets, researchers in Wisconsin have studied one of the most widely used cover crops—cereal rye (also known as winter rye or annual rye, but not to be confused with annual ryegrass)—and identified biomass thresholds that align with three common cover crop goals: reducing nitrate leaching, minimizing erosion and runoff, and suppressing weeds.