Pretend you, the weed seed, didn’t get eaten. It’s time to think about germinating. But you, the weed seed, can only germinate if you get the right ‘cues’. Weed seeds are incredibly smart. A lot of weed seeds will only germinate when they sense ‘pure light’. Light changes as it passes through green leaves. Weeds don’t want competition, so they will wait until there are no other living plants around before they germinate. So, what if you planted a cover crop? The cover crop, alive or dead, is blocking that pure light from hitting the soil, where you and your weed seed friends live. You might never get the cue to germinate.
Are you sold? Here are three ways you can start integrating cover crops into your garden.
First, let’s think about the life of a weed seed. Better yet, let’s pretend we are a weed seed trying to grow in your garden. We’ll start sitting in or on the soil. One of the biggest threats to a seed is something most people don’t normally think about: getting eaten. Mice, crickets, beetles, ants, birds (including chickens) – these things all love to eat the seeds sitting in the soil. Often the seed-eaters are themselves constantly in danger of getting eaten. A cover crop provides protection for seed-eaters. It’s harder for a hawk to see a juicy mouse running along the ground if there’s a cover crop. The mice protected by the cover crop will eat a lot more seeds.
Let’s say you managed to get all the cues you needed to germinate. Congratulations, you are a weed seedling! But your fight is just beginning. The cover crop is hogging a lot of the things you need – light, water, nutrients – it’s stealing resources. And the cover crop is bigger than you, you’ll most likely just get the ‘leftovers’. The cover crop is making your life hard, so you are not going to flourish. And again, there is the threat of being eaten. Mammals love to eat tender little seedlings, and again they love to hang out under the protection of the cover crop, so your chances of survival aren’t great.
Materials high in organic content may reduce the nitrogen available to plants as these materials will require nitrogen during the decaying process. Apply about 2 pounds of a nitrogen fertilizer (such as ammonium sulfate) per 100 square feet prior to mulching. This will ensure that adequate nitrogen will be available to the mulch and crops. If the ammonium sulfate is applied on top of the mulch, much of the beneficial nitrogen will evaporate into the air.
Place a sheet of clear plastic one to four millimeters in thickness over the area. The plastic must lie very close to the soil surface as this maximizes the high soil temperatures necessary to kill seeds. Anchor the edge of the tarp by burying it in a small soil trench around the plot. Be sure to repair any rips in the plastic to insure an air-tight cover and maintain maximum soil temperatures. Soil solarization should be done during the summer months to best utilize the high temperatures and high light intensities. Wait three to four weeks while the sun heats the soil and roasts the weed seeds. Remove the plastic and allow the soil to dry slightly before planting. Do not cultivate soil deeply as this will bring more viable weed seeds to the surface.
Mulches, whether organic or inorganic, are placed on top of the soil to prevent sunlight from reaching weed seeds, therefore preventing germination and growth. Mulching offers an efficient means of weed control, and it also conserves soil moisture. Examples of organic mulches are weathered sawdust, compost, rotted manure, bark chips or other such materials that you know have not been contaminated with chemicals or weed seed. Mulches should be applied 2-4 inches deep on the soil surface.
Some nonchemical methods of weed control are: cultivation, proper site preparation, solarization, mulching, and preventive seed production.
This is a technique that can greatly reduce the number of weeds and weed seeds in a garden area by capturing sunlight to heat the soil to temperatures that kill germinating weed seeds. Irrigate the area to a depth of 3-4 inches. This will encourage the weed seeds to sprout. Cultivate and rake the soil level.
Remove weeds, by hoeing, hand weeding or digging with a shovel or trowel. Weeds are easier to pull with their root systems intact if the soil is moist. This is best done just after a rain or irrigation. Be sure to remove any part of the weed that can regenerate. Shallow cultivation and hoeing control the weeds in the surface soil. When soil is worked deeply new seeds are brought to the surface. The potential weed population is almost endless.
Proper site preparation
Turn the soil with a shovel. Break up clods, rake surface and level. Irrigate and allow weed seeds to germinate. Remove the weeds and repeat the process again before you plant.