GO WHERE THE GRASS IS GREENER SS

cycle is immediately disrupted. That’s where continuous cover and crop diversity come into play to alleviate the strain caused by continuous loss of fertility.

Fertility can be assessed in multiple ways including tissue sampling, soil tests, pre-plant and side-dress nitrate testing, and cover-crop-biomass testing. The cover-crop-biomass test from AgSource is the one I use most often.

I put conservation practices to the test in 2022, with assistance and resources from University of Wisconsin-Discovery Farms, our local watershed group Eau Pleine Partnership for Integrated Conservation and several growers with whom I work. On a nitrogen-use-efficiency trial we were able to produce corn silage that yielded 25.8 tons per acre on only 60 credits of nitrogen with 277 percent nitrogen efficiency using no-till and terminated cover crop. Comparing nitrate soil tests at pre-plant and preside-dress, the plot gained 80 percent more nitrogen – even though we didn’t add any.

How could that have happened? The cover crops stayed active through the winter and into spring, drawing up nitrogen. When the crop was terminated it gradually released it. The cover-crop mix had a carbon-nitrogen ratio of 12:1 to 15:1, which means nutrients were released from the decaying cover crop gradually through spring and into summer That fed the corn just enough along the way, instead of all at the beginning.

In a separate instance, that phenomenon of fertility uptake was seen again in a wheat field harvested for grain and straw. It was then planted with a wheatbrassicas-spring-peas cover-crop mix. Comparing biomass, cover-crop tests taken 12 days apart – Sept. 28 and Oct. 9 the cover crop gained 287 percent dry matter per acre along with extra fertility. In that span the cover crops also brought in 101 credits of nitrogen, 28 credits of phosphorus and a massive 164 credits of potassium.

To put that into context, that’s about the equivalent of 100 pounds of urea, 50 pounds of monoammonium-phosphate fertilizer and 98 pounds of potash. And all that happened within less than two weeks of growth, sampled at the end of September and in early October

What makes this all more fascinating is that the mix performed better than a single-species seeding. In the same field the combine head left a thick strip of volunteer winter wheat. In a snapshot of time in early October, the diverse mix had more accumulated fertility – most notably, 38 more credits of nitrogen and 49 more of potassium. The difference is the diversity of growth and root types interacting with the soil