Strip cropping is a method of farming used when a slope is too steep or too long, or otherwise, when one does not have an alternative method of preventing soil erosion. Strip cropping alternates strips of closely sown crops such as hay, wheat, or other small grains with strips of row crops, such as corn, soybeans, cotton, or sugar beets. Strip cropping helps to stop soil erosion by creating natural dams for water, helping to preserve the strength of the soil. Certain layers of plants will absorb minerals and water from the soil more effectively than others. When water reaches the weaker soil that lacks the minerals needed to make it stronger, it normally washes it away. When strips of soil are strong enough to slow down water from moving through them, the weaker soil can’t wash away like it normally would. Because of this, farmland stays fertile much longer. The term strip cropping also refers to a method of dry farming sometimes used in areas including parts of the Great Plains of the United States and the Prairies of Canada. To accumulate moisture in these dry areas, cropland is periodically left fallow.
The facilitative version of strip cropping can be independent from or a rotational adjunct to the agrobiodiversity version. In alternating strips of productive and non-productive species, nutrient gains are often coupled with some form of insect control, e.g., repellant plant. The non-productive biomass can be hand cut-and-carried or machine mowed-and-tossed onto the productive strip.
The advantages, other than these being farm machine friendly, are enumerated in this chapter (under cut-and-carry systems). The economic answers lie in the vast array of species and spatial possibilities as well as the timing of the cut and carry. Some facilitative strips can be revenue oriented, others cost oriented, depending on whether the strip biomass is directed toward higher yields or economizes on imported nutrients.
Under strip-cropping conditions, alternate parcels of different crops are grown on the same field. The strips with the greatest surface vegetative cover capture soil eroded from upslope areas. Strip widths are dictated by farm implement requirements. To improve erosion control, the strips are usually planted on the contour in a rotation that shifts crops annually from one strip to the next. The most effective strip-cropping rotations include perennial grasses and legumes that alternate with grain and row crops. In arid and semiarid regions, strips may be placed perpendicular to the prevailing wind direction for wind erosion control.
Strip cropping also tends to filter out the soil in the runoff through the strip with the closely grown crop. On the negative side, one crop may tend to harbor (host) plant diseases and pests which are detrimental to the other crop.