Why Should We Put Decomposed Plants Back Into the Soil?

Soil Conditioning

• Adding compost to soil improves soil quality in countless ways, which is why it is a soil conditioner. Compost improves soil texture and structure. The steady addition of compost eventually makes both heavy clay and light sandy soils loamier, helping soil drain well but also holding adequate moisture, nutrients and air for improved plant growth and health. Soil with good structure is easy to turn over during cultivation.

Soil Nutrition

• Compost slowly improves soil nutrient levels. It contains the basic nutrients that plants require for healthy growth including nitrogen, phosphorous and potassium, and essential micronutrients including copper, iron, manganese and zinc. Unlike instantly available nutrients of chemical fertilizers, those in compost are bound up inorganic compounds, which means these nutrients break down slowly and steadily and are taken up by plants just as slowly and steadily as needed. Well-aged compost releases stored nitrogen in the spring after soil warms up, 25 percent in the first year, 10 percent the second and third years and more slowly after that. Adding compost regularly reaps full nutritional benefits.

Soil Chemistry

• Finished compost has a neutral pH, so adding compost to garden soil helps maintain an optimal pH for nutrient absorption and other biochemical processes. According to University of Illinois Extension, high levels of organic matter in soil also help minimize plant injuries due to high salt content and other soil toxins.

Soil Life

• Adding compost to soil improves the overall "life" of soil, which has a positive effect on all soil processes. Compost provides earthworms, centipedes, sow bugs and other active soil creators with a good diet. Their presence indicates healthy soil ecology, meaning that active decomposition and nutrient release are still occurring. Compost also helps check diseases and insect pests. Rich levels of organic matter also support healthy levels of microorganisms critical to nutrient release and other soil processes.