A quick, a step by step guide to bringing life and nutrients back into dead and exhausted soils.
Pictured above is an unassuming little patch of mixed cover crop thriving in the cold, wet soils of early spring at Giving Ground Farm. Here we see a mix of triticale, hairy vetch, winter rye, and winter peas quietly accomplishing the life-sustaining processes of fixing nitrogen, protecting soil from erosion, and adding organic matter to the soil in the form of green manure. Learn more about applying this most economical method of soil building to your garden below!
Building Healthy Soil
So you've removed a sod or weed patch and exposed the soil you want to start growing your vegetable garden in. Now some soil building is almost certainly in order. Nothing exhausts and compacts soil quite like growing year after year of lush grass, being walked on, driven on, and mowed, and with only chemical fertilizers for a nutrient source. But never fear! While the process of rebuilding the soil to a healthy, living ecosystem takes time, it won't take much of your time because most of the work will be done by soil-dwelling bacteria, fungi, and insects. And you can still grow your vegetables in the steadily improving soil!
Before you begin, its good to have an idea of where you are going, so here is a quick list of what a healthy garden soil contains and what you are facilitating when you are building soil.
1. Oxygen: Plant roots, beneficial bacteria, fungi, and soil dwelling insects all need oxygen in the soil to survive.
2. Organic matter: Organic matter feeds beneficial organism and holds nutrients and water where plant roots can access it easily.
3. Nutrients: A healthy soil contains a reservoir of slow release nutrients to feed soil organisms and plant roots.
4. Water: A healthy soil can hold water and make it available for roots, but still drains well and does not become water-logged.
Step One: Add compost
Organic matter in the form of finished compost helps improve soil structure by creating large pore spaces through which air and water can flow, and serves as the nutrient reservoir for your growing plants. If you don't have a finished compost pile of your own, the bagged stuff from the store will do for a small garden. Composted poultry manure or steer manure are most commonly found in this form and will work just fine for this, so long as it is not too woody.
Applying compost is easy. As a general rule, the first year you will want to apply about two inches to the soil and rake it into the top six-eight inches of the soil. You don't need to turn it any deeper than that, compost is naturally found in the top layer of soil where there is the most oxygen. Year two you can reduce it to 1 inch of compost, and a 1/2 inch every year or every other year after that. Contrary to popular belief, you can definitely apply too much compost, throwing soil nutrients out of balance in the process, so stick with these amounts until you would like to do a soil test and make your application more exact. *I've learned a lot about over-application of compost from Steve Solomon's The Intelligent Gardener-
https://www.permaculture.co.uk/book-reviews/intelligent-gardener-growing-nutrient-dense-food. It's a must-read for anyone who would like to start their growth of great produce with caring for and balancing the soil.
As your soil now contains more organic matter you should see the texture gradually begin to improve, becoming more "crumbly" to the touch as soil particles are bound together by beneficial bacteria, fungi, and their by-products. Now that we have seen some results we want to keep going, this is fun.
Step Two: Cover-crop
Cover-cropping consists of growing a crop solely for the improvement and protection of the soil which is not harvested, but is instead incorporated into the soil. "Green manure" is another handy name for cover-crop that may help illustrate its purpose further.
When planting a cover crop, it's often best to grow a mixture of crops together in order to achieve all your diverse soil-building goals. When we cover-crop in the winter at GGF we grow a mixture of triticale, hairy vetch, winter barley, and winter peas. When we cover crop in the summer we grow buckwheat. Lets break your seasonal options for cover-cropping down a bit.
Winter: Winter cover-cropping consists of planting in early fall when there is still enough light and heat for the seeds to germinate and begin growing a bit. We sneak our cover-crop seed in a row as soon as our main season crop in that row is finished, planting into the crop stubble. This time frame can range from late August to late October. It is typically advised to get the cover crop in earlier than that, but I like to harvest my main crop for as long as possible. Though later planted cover crop doesn't get as much of a head start as is "ideal", it still continues to grow in spring and the later planted rows just end up being the rows I choose to plant later in the spring, so it all works out.
Anyway, during the winter growth basically stops, and then resumes in spring. What is happening during this time? Fibrous roots of winter-hardy grains like triticale, rye, barley, and wheat hold on to the soil and help prevent erosion during winter and spring precipitation. Roots of nitrogen-fixing winter-hardy legumes like peas and vetch work with bacteria to convert atmospheric nitrogen to plant-available nitrogen in the soil, becoming the nitrogen next year's crop will use. In spring, prior to needing that space for planting your crop or prior to the cover-crop flowering (whichever comes first), the cover crop is tilled into the soil. Fibrous roots and green tops break down, releasing nutrients and adding organic matter.
Summer: We grow a buckwheat cover crop in the summer. Because most of our field is occupied, we use our buckwheat only in areas where the crop is out by midsummer and we'd like to begin working on the soil there- like the garlic patch. Once the garlic is out in July, we rake in the buckwheat seed. One drawback to summer cover cropping is that you have to irrigate it, and buckwheat needs a lot of water. However, it's just a quick 4-6 weeks before it's incorporated and we let it grow densely to help supress weeds. Buckwheat is very frost sensitive and short days cause it to flower, so it really is just an all-star mid summer cover crop and nothing else.
Cover cropping is very economical if you find the right seed source. We generously cover crop an acre area for around $24 by getting our custom seed mix from Idaho Grimm Growers: https://www.idahogrimmgrowers.com/
Maintenance: Institute a soil-building schedule within your yearly growing schedule
Decide what time of year you are going to apply compost and in what season you will cover-crop. You can alternate which portions of your garden get cover-cropped so the soil is occupied by either the crops your growing or a cover-crop, or cover crop in the winter only.
At Giving Ground Farm we apply our finished compost in the fall, once all harvesting and field clearing is done. We make our own compost, and that schedule works well for us because that is when our compost is done. We also cover-crop about half of the field over the winter. We leave half vacant so that we have bare space to plant our early spring crops. We then summer cover-crop with buckwheat where spring crops, early potatoes, and garlic come out in mid summer. This way, every area in the field gets cover-cropped at some point in the year.
Maintenance: Refrain from using chemical fertilizers and herbicides, overzealous tilling, and working the soil when it is very wet/dry.
Chemical fertilizers contain salts which are toxic to soil-dwelling bacteria and fungi- which are the basis of the entire soil ecosystem. Remember, these guys turn the organic matter you apply into plant-available nutrients so without that food web in a healthy state you will become dependent upon chemical, quick-release fertilizers to feed your plants.
While tilling can be an effective partner in organic weed control and cover-cropping programs, too much tilling can kill beneficial soil organisms, speed the breakdown of organic matter and the release of carbon from the soil into the atmosphere, and destroy soil structure. How much is too much will vary with soil type and climate, but we try to till a certain area no more than once a year, usually in the spring. We plant our fall cover crop into our crop stubble, thus avoiding fall tillage.
Don't work or walk on the soil when it is wet if possible. This compacts and crushes soil pores. The same goes for for very dry soil. Even raking soil when it is very dry can cause erosion- if you can see the dry soil blowing away right before your eyes stop working it! We live in an area where the agricultural fields around us are tilled in the dry fall once the potato crops are out in preparation for a winter cover crop. The potatoes have been drying down so the fields have been not been irrigated and are very dry at this point. By this process, particles of dusty, dry soil are released into the air. And while this dusty air makes for spectacular late summer sunsets, each represents the erosion of a precious resource- the soil!
Read more about dusty western sunsets in the news here: https://www.kuer.org/post/soil-erosion-west-getting-worse-and-air-getting-dustier