Minimizing soil disturbance also helps control weeds
. A soil can have all the nutrients in the world, but weeds can destroy its productive capacity by outcompeting tender crop plants for nutrients and other resources. Frequent disturbance by digging or hoeing perpetuates the problem by dragging weed seed reservoirs from the deeper soil layers to repopulate the surface. By reducing or eliminating surface disturbance, organic growers can exhaust the seed bank in the surface layer and create a more productive soil environment. Mulch, key to reducing temperature and moisture extremes in the soil, can also improve soil quality by shading the soil surface and putting surface seeds into dormancy until they can be decomposed by the well-fed soil fauna.
Crop rotation is the practice of growing a sequence of different types of crops on the same field or garden bed over several years. While the prime reason to follow broccoli with bell peppers might be to control cabbage moths, crop rotation also helps maintain an appropriate balance of nutrients. The result is healthy plants that can better resist disease. For example, too much soil nitrogen
makes tomatoes more vulnerable to late blight than those growing with more appropriate nitrogen levels. Rotation also aids in cleaning out diseases
like fusarium wilt, which can live in soil for up to 7 years. To reduce pathogens in the soil and maintain optimum soil health, Cornell University plant pathologist Margaret Tuttle McGrath, Ph.D., recommends a rotation that is longer than 7 years.
Organic soil health is complex, but the tools used to implement or restore it are simple.
Alison M. Grantham is the Research Manager at the Rodale Institute