Mowing Sorghum Sudan & Cowpea Cover Crop – Wow That’s Alotta Mulch!

I’ve spent this whole weekend mowing our cover crop on our neighbor’s 25 acres, and I’m still not done!  Wow, the sorghum sudan got away from us big time!  The average height was around four feet, but in some areas, it was starting to form seed heads, and the tops reached up to 10 feet.  It was kinda terrifying mowing stuff this tall, especially on a slope, but fun at the same time.

When sorghum sudan gets this tall, its stems can get close to an inch in diameter.  This isn’t good for our plan to rotovate (shallow-till) all the plant matter into the soil so it can decompose and eventually transform into organic matter.  Stems this thick are very fibrous and will take a long time to break down, and we need good decomposition so rough plant matter won’t foul the planter when we plant our winter cover crop in late August. We’ll see what happens!

Thankfully, our bush hog is a good shredder.  Alfred at AgVerra advised us to bush hog the crop twice.  The first time we set the bush hog at the tallest setting, going very slowly in our tractor’s second-lowest gear.  The second time we drove faster with the bush hog at the lowest setting to get a good shred on the thick standing stems.  This worked really well.  It takes forever, of course, but the huge amount of plant matter will hopefully be worth it!

Going so slowly on the tractor gave me plenty of time to observe the crop.  The cowpeas looked really good in most places.  Even though they were getting shaded by the soghum sudan, the cowpeas were dark green, healthy, and just about to flower.  I’d definitely plant this combination again, using more cowpeas and not letting the sorghum sudan get so tall!

It’s nice to think about how much good this cover crop is doing for the soil!  The size of plants above ground are mirrored in the size of their roots below ground.  With a crop this tall and thick, that is A LOT of root mass below ground!  When the crop dies, the roots will decompose, transform into some organic matter, and create lots of channels in the soil.  These channels are nice airways, allowing for better water infiltration and making good tunnels for earthworms.  Also, since plants are photosynthesis factories, shredding all of this plant matter and giving it to the soil means we’re feeding the soil all the carbon, hydrogen and oxygen that the plant has assimilated from air and water, not to mention all the plant goodies – carbohydrates, vitamins, plant hormones, etc.  Since we’re not removing anything from the fields, the net benefit to the soil is huge!

We’ve heard that after a good cutting, sorghum sudan will send down even deeper roots and put on more leafy growth.  This will be great for rotovating some green matter into the soil to mix with all the brown mulch material.  We plan to rotovate in early August.  We’re working on making a front-mounted boom sprayer for our tractor.  We aim to spray the mulch with microbes, enzymes and sugars to speed the decomp process and to rotovate all in one trip across the field.  We’ll let you know what happens!


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