Severe flooding in the Midwest is a reminder of one of the social benefits of healthy soil. Dick and Sharon Thompson's 300-acre crop and livestock farm in Iowa is like a huge sponge. Rain and melting snow sinks into their absorbent soil. Millions of earthworms per acre perforate the soil so rain can quickly penetrate, and a high level of organic matter from the Thompsons' careful management of livestock manure and crop residue gives the soil outstanding moisture-holding capacity. As a result, the ditches between the Thompsons' fields and the road are virtually free of silt.
In contrast, their neighbors' ditches must be dug out nearly every year. In their fields, insecticides kill most of the earthworms, and the soil surface is crusty. Rain puddles and forms gullies, washing the sickened soil away in a torrent of runoff water, filling the ditches with silt and swelling the already overflowing creeks and rivers.
Healthy soil is the key to healthy crops and health-enhancing foods. A Japanese tomato grower using Nature Farming (as taught by philosopher Mokichi Okada) provides an outstanding illustration. Conventional tomato growers never plant tomatoes in the same soil two years in a row because the accumulated disease pathogens will destroy the roots of the second crop. Consequently, less profitable crops must be grown for two to five years before tomatoes are reintroduced to the field.
But a Japanese farmer using the Natural Farming technique has harvested his 19th consecutive crop of beautiful and delicious Nature Farming tomatoes, and often gets outstanding yields (100 tons per hectare)! How does he do it?
After each tomato crop is finished, he removes and composts the tomato vines, applies last year's finished compost to the soil, and plants a cover crop of sesbania, a fast- growing tropical legume. When the cover crop is five to six feet tall, he flail-chops it and turns it under the soil surface as a green manure.
Later, when he transplants the new tomato crop, he also plants an onion, leek, or garlic plant next to each tomato. The roots of these Allium-genus plants growing among the tomato roots support a beneficial bacterium (Pseudomonas cepacia) that repels and inhibits root pathogens, such as fusarium, thereby protecting the tomato plant and ensuring a healthy crop. The secret is keeping the soil healthy and interplanting with a plant that provides habitat for the natural enemies of the disease-causing organism. Just like a healthy person who rarely needs medicine, healthy soil rarely needs synthetic chemical pesticides and fertilizers.
For a long time, scientists were puzzled by the fact that crops on organic farms in rain-fed areas are less vulnerable to moisture and heat stress on hot, dry days in late summer, than the wilted fields of their conventionally farming neighbors. Scientists now explain this seemingly mysterious phenomenon as the result of a symbiotic relationship between farm crops and a beneficial fungus called VAM (vesicular arbuscular mycorrhizae).
VAM harmlessly infects crop roots, then spreads far out into the soil, helping the plant reach moisture and nutrients far beyond the grasp of the roots. Scientists have found that the mass of the VAM can be 100 times greater than that of the roots.
In return for providing abundant water and nutrients to the crop, the VAM take from the plants small amounts of sugar photosynthesized by the leaves. It's a splendid partnership. And it explains why organic farms and Nature Farms get crop yields far higher than agronomists predict based on the nutrients available in the soil and those added in compost or manure – without resorting to chemical fertilizers. Crop rotations and other practices used on organic and Nature Farms enhance VAM activity.
The soil is a living organism. With proper management, the soil thrives, breathes, drinks in the falling rain, and supports healthy crops.