Why Better Soil Means Better Vegetables
The fascinating story of the innovative, nontraditional, often surprising things some scientists and farmers are doing to revitalize depleted soil.
It isn't just dirt
Kris Larson, who was head farmer at La Vista CSA for four years, talked frequently about the quality of the farm’s soil. He marveled at its richness and with good reason. Years before La Vista came into being the property was owned by a family whose cow pasture was once located where our fields now stand.
There’s nothing like good ol’ manure to keep the soil fertile and lush.
Before I really knew anything about the farm and growing vegetables, I would think, “What’s with all the talk about the soil? Dirt is dirt.”
Ah, but it isn’t.
Just as you wouldn’t build a house on a weak foundation, you don’t want to plant your garden in poor soil. You want as strong a foundation for your plants as you can make. And making soil – building your garden from the ground up – is going to reap rich rewards in the long run. Good garden soil provides roots with the nutrients necessary for plant growth.
The building blocks of soil
The texture of soil, soil pH and the nutrients in soil all play a factor in how well plants grow.
The amount of clay, sand and organic matter makes a difference in the soil texture and affects how well it holds moisture and nutrients. Pick up a handful of soil and squeeze it. If it remains a clump in your hand, it has too much clay. Conversely, if it slips through your hands, it’s too sandy.
The best soil is rich in organic matter, holds moisture and is full of air pockets. This type of soil will hold nutrients longer, unlike sandy soil in which water drains away, taking nutrients with it.
Some of the best soil I encountered was when my husband and I lived in Virginia. The earth was black and rich and we had a marvelous garden the two years we were there that produced so much we had trouble giving it away.
Soil pH measures how acidic or alkaline the soil is. The optimum pH level for growing vegetables is between 6.5 and 7.0. At this level, beneficial bacteria and fungi occur at the greatest number. These bacteria and fungi help release nutrients from organic matter in soil and provide protection to plants against disease-causing microbes.
The most important plant nutrients are nitrogen, phosphorus and potassium. Plants draw upon these nutrients to grow. If the soil lacks these nutrients, the plants will do poorly.
Nitrogen (N) helps plants with rapid growth, increasing seed and fruit production and improving the quality of leaf and forage crops. It is a part of chlorophyll, the green pigment of the plant that is responsible for photosynthesis.
Phosphorus (P) also is essential for photosynthesis. It helps with the transformation of proper plant maturation, encourages blooming and root growth and effects rapid growth.
Potassium (K) is absorbed by plants in
larger amounts than any other mineral element except nitrogen. This nutrient
also helps in photosynthesis, fruit quality and reduction of diseases.
Getting your soil tested
Soil should be tested before starting a new garden or if it’s an established garden, soil should be tested every three to five years. The best time is in the fall so that any changes in the pH can be worked over the winter. Your local Cooperative Extension office or agribusiness can test the soil for you. Digging 6-8 inches deep, take a trowelful of soil in 10 different spots in your growing area. Mix them all in a bucket and remove a cup of soil. Let it air dry. When it’s dry, put the soil in a clean ziploc bag and send it off for analysis. You should get results back in a couple weeks.
If test results show that the pH is less than 6, it will be necessary to apply ground limestone to raise the pH and reduce acidity. The test lab will make recommendations on the amount to add. Work the limestone in the top 6 inches of soil.
If your soil turns out to be too alkaline, you need to increase its acidity, which isn’t as easy. The most common additives are granulated elemental sulfur and sphagnum peat moss.
As the worm turns
Earthworms are one of the most important soil-building creatures a garden can have. They are the primary consumers of organic matter and their fecal matter – called castings – is rich in carbon, a product of decay of plant material. Carbon is a key building block for fertile soil.
Castings provide a way to keep carbon in garden soil as well as also improving its structure, keeping it loose and crumbly. When castings are numerous, you can assume the soil is rich and productive.
The best way to keep earthworms around is to create a better environment for them. Do this by increasing the amount of organic matter in the soil, watering during dry periods, tilling the soil and using mulches.
Starting in February, each of our farmers, past and present, has built the soil used for sowing seeds in the greenhouse. Eric Stevens, our current farmer, uses the following when building soil at La Vista.
- Rice hulls – a 1 to 3 ratio. This is a good alternative to perlite and is used for drainage
- Peat moss – a 2 to 3 ratio
- Worm castings – should be between 5% and 15% of the mix
- Lime – 1 quart
- Bone meal – ¼ cup – about a large yogurt cup
Kris practiced biodynamic farming. He recognized that the soil itself is alive and this vitality supports and affects the quality and health of the plants that grow in it. Without healthy soil, you won’t have healthy plants.
This is the second in a series of monthly hubs I’ll be writing in 2011 about La Vista Community Supported Garden in Godfrey, Illinois. I joined La Vista in 2005 and became a member of its board of directors a year later. This series – La Vista: Nurturing land and people – will take the reader through a year at the farm, sharing the struggles and triumphs of operating a CSA and the benefits of membership. I hope you find this series useful and interesting and, as always, feel free to leave a comment.
Next month: Spring Greens