Control of soil-borne plant diseases by the “rigolen” method of plowing means the careful inversion of the surface soil (usually about the first foot) with soil from below. Knowing that crops generally produced less and less when grown repeatedly without rotation in the same soil, but not knowing why, an unknown farmer developed the rigolen or soil-inversion technique over a century ago to counter diminishing yields. Thus, rigolen plowing (spades were used in the early days) was developed before the causes of soil-borne plant diseases were known. Actually, rigolen plowing is a method for controlling soil-borne diseases by rotation—but the soil, not the crop, is rotated. This three-year study was conducted to determine whether the rigolen method would control soil-borne diseases today—and especially Verticillium wilt of cotton.

Research from which the: progress report was prepared was sup ported in part by the California Planting Cotton Seed Distributors