Strip cropping is an agricultural conservation practice defined by planting different crops in alternating, relatively narrow bands on the same field. This technique systematically alternates between erosion-susceptible crops, such as row crops, and resistant ones, like grasses or legumes. The method was developed in the United States during the 1930s in response to the severe soil loss of the Dust Bowl era. Its fundamental purpose is to establish a natural barrier that interrupts the forces of wind and water. The practice stabilizes the soil, promoting long-term land productivity.
Understanding the Physical Layout
The effectiveness of strip cropping depends on adapting the physical layout to the specific landscape and environmental challenges.
Contour Strip Cropping
This common application uses alternating bands of crops that follow the natural elevation contours of the land. Used primarily on sloping fields, the strips are oriented perpendicular to the direction of water flow, which is crucial for controlling runoff.
Field Strip Cropping
Where the land is relatively flat or has only a slight slope, this method uses parallel bands across the field. It is designed to mitigate wind erosion, with tall crops acting as a windbreak to protect the adjacent, more exposed strips.
Buffer Strip Cropping
This variation involves establishing permanent, non-harvested vegetation, such as perennial grasses or shrubs, on particularly steep or highly erodible sections. These permanent buffers are strategically placed between the farmed strips to provide maximum long-term protection.
Strip width is also carefully determined, often sized to accommodate multiple passes of farm equipment for efficiency. The width must also be narrow enough to ensure the protective crops effectively shield the erosion-prone ones.
Primary Role in Soil and Water Conservation
The most direct purpose of strip cropping is the physical mitigation of soil loss caused by both water and wind forces.
Controlling Water Erosion
In areas prone to water erosion, strips of dense, close-growing crops—such as hay, small grains, or forage—function as natural sediment filters and small dams. When rainfall causes surface runoff, the dense canopy and extensive root systems of these protective strips slow the water’s velocity. This reduction in speed causes suspended sediment particles, including valuable topsoil, to settle within the dense vegetation before they can be carried off the field.
By slowing the runoff, the strips significantly enhance water infiltration and soil moisture retention. The protective strips effectively reduce the formation of rills and gullies by interrupting the sheet flow of water down a slope. This mechanism also limits the transport of dissolved nutrients, such as nitrogen and phosphorus, and any associated pesticides into adjacent waterways.
Controlling Wind Erosion
For wind erosion, the purpose shifts to utilizing the height and density of alternating crops to physically reduce wind speed across the soil surface. Tall, upright crops, like corn or sorghum, act as aerodynamic windbreaks that dramatically lower air velocity near the ground in the adjacent strip. This reduction prevents the wind from detaching and carrying away fine soil particles.
Broader Ecological and Economic Benefits
Beyond the immediate protection of soil, strip cropping provides a suite of broader ecological and economic advantages.
Ecological Benefits
The practice of planting diverse crops in close proximity enhances local biodiversity by creating varied microhabitats within the field. These strips of vegetation, particularly the perennial grasses and legumes, offer shelter and foraging areas for beneficial insects, including pollinators and natural predators. This increased habitat diversity aids in natural pest suppression, reducing the pressure from harmful insects and diseases on the cash crops. The physical separation provided by a non-susceptible crop strip can limit the spread of a disease or pest from one strip to the next. This natural pest control can lead to a reduced reliance on chemical inputs, which lowers production costs.
Economic Benefits
Economically, planting multiple crops in a rotation provides risk management against market fluctuations or weather-related crop failure, as the farm’s income is not dependent on a single commodity. Furthermore, the inclusion of nitrogen-fixing legumes, such as clover, enriches the soil, leading to improved soil fertility and structure over time. This improvement in soil health and moisture retention contributes to more robust and stable crop yields.