Q: After two years of trying to grow a vegetable garden, I am almost ready to give up. You know—three strikes and you are out. I have been doing some reading and am now more confused than ever, but it appears that the soil is the problem. The garden is in full sun, and I use a drip hose to keep it watered. There are so many things I could buy and add to the soil. What do you think?
A: You are right; there are a lot of products out there that may or may not be useful. Some are unnecessary or even harmful. A soil test may help. Talk to your local university extension office to see where they recommend you send a sample.
In the meantime, remember, as I say in my book: Soil is not dirt. Plants need four things to grow: air, sunlight, water, and soil. Dirt is unwanted debris. Soil is a combination of air, water, chemicals, minerals, living organisms, and organic matter arranged in a stable structure. Soil is partly solid, partly liquid, and partly air.
The ideal Goldilocks “thrive range” soil depends on what you are trying to grow. An ideal soil for a cactus is different from an ideal soil for a waterlily. The cactus soil will have a very high pore space volume and low water retention. The waterlily soil will have all of the pores filled with water.
The ideal garden soil for most vegetables and many annual flowers is about 50 percent solid material (45 percent mineral and 5 percent organic matter), up to 1 percent living organisms and the rest pore space. The pores will vary in water and air content depending on rain and irrigation.
How often do plants use water? The answer is pretty much all the time. Chemicals in the soil move into the plant with the water. Water evaporating off the leaves cools the plant and helps move the chemicals around in the plant. The reason we don’t have to water plants constantly is that the soil acts like a sponge. Like a damp sponge, soil holds water in the small pores and allows air circulation in the large pores.
Most suburban and urban topsoils are too thin and too compacted. Imagine a small sponge being squeezed: It will not hold much water or air. Plants that are growing in these kinds of soils are often growing in the survive range and not the thrive range of good soil conditions. They will grow some and produce some fruit but not at the level they would if the soil were better. It is hard to give the plants the proper amount of water if the soil sponge isn’t big enough to hold water and the pores that should be filled with air are filled with water, drowning the roots.
Just about every type of soil can be improved with just one product: organic matter. As mentioned above, it doesn’t take much organic matter to make a difference. Sandy soils that drain too fast because they have too many large pores are helped because the organic matter adds a lot of spongelike small pores and nutrients that are lacking. Compacted soils benefit from being loosened up with the compost. Soils lacking in nutrients benefit as the compost breaks down into nutrients plants can use. High pH soils benefit as the compost is most often acidic.
Compost and organic matter come in several different kinds of bags and in bulk. When I am trying to improve soil, I like using several different kinds and mixing them all together to get the biggest benefits from each one. Cover the existing soil with at least 2 inches of compost and mix it into the top 6 to 8 inches of soil. In the long run, don’t rototill the soil, as that hurts more than it helps.
For a lot more information on garden soil, check out the videos in “Chapter 2 Plants and the Environment” on the Greener View YouTube channel.
