How to Turn a Spent Cover Crop Into Compost Mulch Or Sheet Mulch In Place

Weeds that go to seed can serve as an effective cover crop that protects and feeds the soil, provided they’re cut before they sprout and spread.

Start with plain brown cardboard (bike shops and kayak or canoe stores often provide huge boxes that you can collect free). Next, add a layer of carbon such as manure or straw.

Composting

Sheet mulching is a method of building soil with layers of organic material laid directly over an existing garden bed, providing an easy and clean way of composting without all the mess and smell typically associated with traditional compost piles.

Launch with a layer of cardboard (plain brown corrugated, non-glossy and unprinted), wet it down, and cover with 3-inches thick layer of manure or green waste without seed heads – or any other source of nitrogen for maximum fertilization.

Follow your nitrogen layer with an equal-sized layer of carbon material such as straw, wood chips, hay, paper and cotton mulches, hedge clippings (not laurel or cedar), sawdust, shredded barks, tops from perennial plants (if they’re not too weedy), buckthorn branches, sassafras and bracken fern dregs from pond bottoms etc. Once again a handful of finished compost will help inoculate this layer with beneficial organisms to accelerate decomposition process and kick start decomposition processes.

Sheet Mulching

Sheet mulching is a gardening method in which a layer of cardboard, newspaper and other organic materials is spread over soil in order to cover weeds while simultaneously decomposing into it over time, creating an ideal growing medium.

Start with a layer of nitrogen-rich materials, such as composted manure, shredded grass clippings, spent annuals, fruit/vegetable scraps, coffee grounds and alfalfa pellets. Place this layer above a carbon layer consisting of cardboard, newspaper and dried leaves (another great use for those fallen leaves!).

Next, sow a nitrogen-fixing legume such as hairy vetch or crimson clover to enrich the soil’s biomass, improve structure, and allow better water infiltration. For best results, sow these seeds early fall so they have time to grow over winter before being worked in as soon as spring arrives. Use a harrow or rototiller with short, chopping motions when cultivating these into your soil; this increases seed-to-soil contact which is key for successful germination.

Spreading

Sorghum sudangrass is an excellent way to capture any nitrogen that might otherwise be consumed by other plants in your garden, making it an ideal option after food crops have been harvested for the year. Furthermore, this species makes for one of the easiest cover crop species to cultivate in small spaces; you can let it reach full height before cutting it when pollen shed occurs in early summer (around May here) for mulch or carbon for your compost pile, plus saving its seed as mulch or new plants for next season!

Mix grasses like winter rye or wheat with legumes such as hairy vetch, crimson clover or Austrian winter peas for an attractive mix. Add weed suppressants like alyssum or white clover as an additional measure to attract pollinators while protecting your crop from potential threats like drought. Make sure the mulch remains moist during germination and initial stages of growth to maximize success!