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This is Gwen Outen with the VOA Special English Agriculture Report.

Clay soil is a problem for soybean farmers. When the soil is dry, the clay shrinks and breaks up. This condition damages the root system of the plants.

A few years ago, two United States Agriculture Department researchers made a discovery. They found a simple way to grow more soybeans in dry soil that contains a lot of heavy clay.

Soybean farmers with heavy clay soils usually till the earth about ten to fifteen centimeters deep. The researchers found that preparing the soil to a depth of thirty to forty centimeters is better. The seeds are still planted about two to three centimeters below the surface.

The system of preparing the soil this way is called subsoiling. It breaks up hard areas of soil that form when the clay dries. And it does not harm crop materials on the surface.

Subsoiling is done with a device that looks something like a large hook to catch fish. Farmers pull it through the ground to break up the soil structure.

Subsoiling permits water to reach areas below the surface quickly. More water is stored in the soil than would be with traditional ways.

Increasing the ability of the soil to hold water produces bigger crops. It also helps the environment. Less water runs off the land. And less soil is washed away. The researchers said that subsoiling is probably not needed every year.

Richard Wesley and Lowrey Smith made their discovery at an Agricultural Research Service laboratory in the state of Mississippi. They found that farms with deep subsoiling produced almost fifty percent more soybeans than farms with traditional methods.

The farms with subsoiling produced, on average, more than four hundred seventy kilograms of soybeans per hectare. Farm with traditional planting, but without watering systems, produced three hundred twenty kilograms per hectare.

Lowrey Smith also found improvements with cotton. Studies in the past showed that subsoiling clay soil in the spring does not improve cotton harvests. In the spring, the soil still holds rainwater. So the subsoiling process is unable to change the soil structure to prepare it for cotton production.

Mister Smith did his studies in the fall, when the soil was dry. He found that subsoiling in the fall increased harvests of cotton, just as with soybeans.

This VOA Special English Agriculture Report was written by Avi Arditti. This is Gwen Outen.