Cover Crop Part 3
Thinking Ahead for Terminating Options
We can all be thankful for the recent rains that came just as harvest wrapped up! While we all like long soaking rains, too often, poor soil structure from tillage, compaction, over-grazing, low soil organic matter (SOM), or deficient soil microbial life results in soil erosion and run-off, or ‘puddling’ (low infiltration). The rain ‘puddles’ on the field from a combination of factors including compaction or the lack of porosity, preventing all the rain from soaking in – at least not in a timely manner.
It’s never too late to change the situation by planting cover crops. Our soil can recover organic matter & increased infiltration by applying soil health principles, reducing costs, while increasing ROI. At least cover crops planted during the drought of this September and October, finally germinated in November. Depending on temperatures through early December, the cold hardy crops will inch out their crowns before the ground freezes. By early February when things start to thaw, the covers will take off!
Are you ready? Late-winter grazing may be an option in March…. But do you have a plan for terminating those green covers by April or May? It’s been standard to spray an herbicide at termination, prior to planting. Practical Farmers of Iowa, completed 8 years of trials comparing combinations of practices, roller crimping and reduced rates of herbicides.
As discussed in the previous article last fall, “planting green" is a manner of terminating the green standing cover crop prior to, during or after planting with the use of a roller crimper. There are various options and considerations, summarized in this video clip: The Low Down on Roller Crimpers. Roller crimping is the process of rolling over the vegetative stems and leaves of the cover crop with a cylinder having chevron or horizontal blades or crimpers. The crimpers flatten and crush the plant stems to leave behind a thick mulch layer. Though not without risks & benefits, there are some keys to success.
Roller Crimpers leave behind a thick green layer of biomass on the soil surface, available to microbes in the soil. First fed by the cover crops’ root exudates, these microbial digesters are the same microbes (bacteria, algae, fungi) that help build water-stable soil aggregates, increasing porosity and water infiltration, while cycling soil mineral nutrients through plant rhizophagy. While suppressing early weed growth and allowing a slightly cooler soil temperature throughout summer, laying down green residue will encourage increased microbial activity and nutrient cycling as microbes and fungi decompose it. The microbes will boost bioavailability of (free) organic nitrogen, ahead of the following cash crop.
If the crop is terminated with an herbicide, the ‘no-longer-green’ residue is not as bioavailable because it’s been killed, (the fancy word, ‘desiccated’ means removing the moisture, or life, in the plant tissues).
Tinkering & timing are usually required to get the right set up working for your production system, as in all adjustments with all new implements. But what better way to spend some time in the shop this winter with a neighbor or family member building a roller crimper?