Naturally Bug-Free (13 page)
Read Naturally Bug-Free Online
Authors: Anna Hess
Healthy soil in a no-till garden will be dark and will hold together due to the work of microorganisms.
Why is it so important to increase the organic matter levels of your soil? Organic matter acts like a buffer, evening out all kinds of problematic soil conditions. Soil high in organic matter will suck up excess water during rains without becoming waterlogged, then will let the moisture drip back out to keep plants healthy during ensuing droughts. Organic matter clings to soil nutrients that otherwise might be washed away, and it feeds microorganisms that help your plants. That's why good gardeners crave dark, aerated soil high in organic matter and do everything within their power to increase their organic matter levels over time.
Unfortunately, if left to its own devices, mainstream agriculture generally decreases the amount of organic matter in the soil every year. Microorganisms slowly break down organic matter into food, some of which they pass on to plants, and this process can lower your organic matter levels very quickly if you add lots of air to your soil by tilling the ground. Although the decomposition process is slower in no-till gardens, even these spots lose organic matter every year unless you add compost or other amendments to top off the soil's organic-matter supply.
Especially in the early years of a garden, it's handy to add a lot more organic matter than the soil will use up that year, since the residual organic matter will stick around and increase the quality of your growing area. While I recommend compost to keep established soil in good condition, you'd have to add quite a lot to bring poor soils up to par, and all that compost-moving will be hard on your back (and probably on your wallet). To boost organic matter levels quickly, sustainable farmers turn to cover crops.
How much organic matter can you add with cover crops? Quite a bit—you'll likely see darkening of your soil within a year or two of including cover crops in your rotation. My favorite cover crops clock in at 6,000 pounds of dry matter per acre (for buckwheat), 8,000 pounds of dry matter per acre (for oats), 11,700 pounds of dry matter per acre (for oilseed radishes), and 10,000 pounds of dry matter per acre (for rye) when grown in optimal conditions. (Sweet potatoes are a less-traditional cover crop, so data on their dry matter accumulation isn't readily available.) The actual amount of organic matter you grow will depend on your soil conditions, but those pounds of organic matter will definitely add up to a healthier garden.
How to kill cover crops
After deciding between growing nitrogen and growing organic matter, the other main factor to consider when choosing cover crops for a no-till garden is—how will you ensure your cover crop doesn't keep growing as a weed and out-compete your vegetables? While you
can
dig up cover crops or till them in if you're desperate, it's better to choose crops that are easy to kill without disturbing the ground.
If not killed correctly, cover crops can turn into a weed problem in your garden.
In the summer, mowing is the best way to kill cover crops in a no-till garden. Only a few cover crops are easily mow-killed, though, and even with those that mow-kill well, you'll want to plan your garden season so you can allow the crops to reach full bloom (but not set seed) before cutting them down. Depending on the size of your garden, you may use a lawnmower, weed-eater, or scythe to do the mowing, or might simply yank up handfuls then lay the roots on top of the leaves on a sunny day. The latter method is actually my favorite with buckwheat in the summer garden since I can often pull up a bed of buckwheat by hand in the same amount of time it would take to put the blade on my scythe or to get the gas mower started.
My other favorite method of killing cover crops in a no-till garden is to let winter do the work for me. Here's where those of you gardening much further north or south than my zone-6 garden will have to do some experimenting (although
Managing Cover Crops Profitably
does provide zone-related tips on where certain crops will winter-kill). When I plant oilseed radishes and oats in the fall, cold weather naturally wipes out nearly all the plants during the winter, producing a mulch that rots into the soil by early spring (for oilseed radishes) or by early summer (for oats). Later sections will provide planting dates for those of you who want to experiment with winter-killing.
Laying down a kill mulch is a sure-fire way to get rid of cover crops that didn't die when you asked them nicely.
After a month under cardboard and straw, annual ryegrass was fully dead and partially rotted into the soil.
Although mow-killing and winter-killing are my favorite ways to kill cover crops, it's worth having a couple of other techniques up your sleeve in case your experiments don't go as planned. A kill mulch is an easy way to kill just about any plants as long as you have a month or two to wait before planting the next crop. Simply mow your cover crops as close to the ground as you can, lay down corrugated cardboard (being sure to overlap the edges by at least four inches so plants can't sneak up between layers), then top it all off with straw (or another vegetable-garden-appropriate mulch). Lack of sunlight will kill all but the most ornery plants in short order, at which point you can either cut holes in the cardboard to plant directly into the soil, or can move the cardboard to kill mulch a new garden area.
If all else fails, pull your cover crops up by the roots.
If you don't have time to kill mulch and you really need to get rid of those cover crops, you'll be forced to pull them up by the roots. I actually use this method often with buckwheat, as I mentioned above, but weeding out most other cover crops will be a lesson in patience. Good planning ensures you won't need to pull up cover crops by hand very often.
Table of Contents
Chapter 1: Pest-invertebrate identification
Chapter 2: How to promote the good bugs
Part 2: Ecosystem-level bug control
Chapter 4: Letting nature take its course
Chapter 6: Choosing resistant plants
Chapter 7: Keeping plants healthy