By Scout Nelson
A recent Field Notes podcast by UMN Extension focused on the role of cover crops in nutrient cycling and water use. The discussion emphasized how management should adjust based on weather, soil, and crop goals.
Researchers observed that cereal rye is a strong option due to its winteriness. However, the timing of termination plays a major role. Early termination of rye produces less biomass, while delayed termination increases biomass but also water use in spring. This can be risky in dry conditions, as excessive water use can reduce soil moisture for the next crop.
Garcia y Garcia shared that termination timing affects biomass more than the seeding rate. For example, rye planted at about 30 lb/acre can yield similar biomass to higher seeding rates if terminated late. Delayed termination boosts nitrogen uptake, with rye at 12 inches tall holding about 3.5% nitrogen.
A key study showed that 60% or more of the nitrogen in rye can become available within 10 days after termination. However, high carbon-to-nitrogen (C: N) ratios in root biomass can delay nitrogen release, affecting nutrient availability.
Different cover crops serve different purposes. Rye is great for nitrogen scavenging. Radish and turnip cover crops also capture phosphorus and potassium. Legume cover crops can add nitrogen, but only if they grow long enough.
"Terminate when rye is less than 8 inches tall to minimize the risk of N immobilization and reduced corn yield potential."
Cover crops can impact corn yields, so nitrogen management must be adjusted accordingly. If biomass exceeds 1,000 lb/acre, using starter nitrogen or sulfur near the planting row is advised.
Overall, flexible management and thoughtful planning are essential for making the most of cover crops.
Photo Credit:gettyimages-eugenesergeev
Categories: Minnesota, Crops, Weather