Strip farming
Strip farming, also known as strip cropping, refers to the systematic planting of crops in narrow strips or bands across a field. This agricultural practice aims to address several environmental challenges associated with large-field farming, such as soil erosion caused by wind and water, and the loss of essential nutrients from the soil. By creating a pattern of alternating strips—typically of hay plants or grains alongside cultivated row crops—strip farming helps trap minerals and pollutants, while also providing habitats for wildlife.
Historically, strip farming emerged in response to the enclosure movement in postmedieval Great Britain, where land consolidation led to larger fields that were more vulnerable to erosion. Recognizing the environmental degradation from expansive farming practices, strip farming was developed in the 1930s as a soil conservation technique. This method can significantly reduce soil erosion—by 65 to 75 percent on sloped land—and supports sustainable agriculture by allowing for crop rotation and nutrient replenishment.
The design of strip farming is tailored to the specific characteristics of the landscape, including slope and wind conditions, ensuring that it effectively mitigates erosion and promotes agricultural productivity. Overall, strip farming represents a harmonious integration of crop production and environmental stewardship.
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Strip farming
DEFINITION: The systematic planting of crops on narrow strips or bands of land
Strip farming helps to alleviate several environmental problems associated with large-field agriculture at the same time it improves crop production: It reduces soil erosion from wind and rain; traps minerals, metals, fertilizers, pesticides, bacteria, and pathogens before they leave cultivated fields; and provides habitat for wildlife.
The origins of strip farming can be traced to the enclosure movement of postmedieval Great Britain. Landlords consolidated the small, fragmented strips of land farmed by tenant peasants into large block fields in an effort to increase agricultural production to meet the demands of growing human populations. A peasant plot was typically 0.4 hectare (1 acre) in size: 201 meters (220 yards), or 1 furlong (the distance a team of oxen could plow before resting), in length and 20 meters (22 yards) in width (the total area being the amount of land one team of oxen could plow in one day). After enclosure, fields were 40.5 hectares (100 acres) or more in size. Larger fields were more productive, but the soil in such fields was also more exposed to wind and water and nutritional exhaustion.
As agricultural production gradually shifted to new lands in the Americas and colonial Africa, farmers continued to use large-field farming techniques and developed large-field plantations. By the early twentieth century, all readily tilled lands had been opened by the plow and were suffering the effects of water and wind erosion. Strip farming, also known as strip cropping, was developed as a soil conservation measure during the 1930s. During the 1960s, strip farming became an important tool to prevent water and air and improve wildlife habitats.
Wind erosion begins when wind velocity at 0.3 meters (1 foot) above soil level increases beyond 21 kilometers (13 miles) per hour. Wind moves soil by saltation and surface creep. In saltation, small particles are lifted off the surface, travel ten to fifteen times the height to which they are lifted, then spin downward with sufficient force to dislodge other soil particles and break earth clods into smaller particles. Surface creep occurs when particles too small to be lifted move along the surface in a rolling motion. The wider the field, the greater the cumulative effects of saltation and surface creep, leading to an avalanche of soil particles across the widest fields even during moderate wind gusts.
Water erosion begins when rain or flowing water detaches and suspends soil particles above the surface and transports them down slope by splash or runoff. Water ice crystals expand, then contract when melted, dislodging soil particles and making them available for both water and wind erosion. Water also leaches nutrients and chemicals from the soil, causing the soil to experience both loss and an increase in salts and acids.
The US Department of Agriculture computes annual soil loss from agricultural and developed land using the formula A = RKLSCP. In this formula, A equals annual soil loss, R equals the amount of rainfall on the plot, K equals the erosion factor for the type of soil on the plot, L equals the length of the slope on which the plot is located, S equals the angle of the slope, C equals the type of crop or soil cover on the plot, and P equals the presence of management conservation practices such as buffers, terraces, and strip farming. Soil loss tolerance—that is, the amount of soil that can be lost without any reduction in productivity—is computed for each plot. Farmers and developers reduce soil losses to tolerance levels by reducing soil to wind and rain and by utilizing conservation practices such as strip farming.
Strip farming reduces field width, thus reducing erosion. Large fields are subdivided into narrow cultivated strips. The planting of crops along the contour lines around hills is called contour strip cropping. Another variation is field stripping, or the planting of crops in strips across the tops of predominant slopes. Crops are arranged so that a strip planted with hay plants (which include grasses, herbaceous plants, and legumes, such as clover or alfalfa) or a strip of close-growing small grain (such as wheat or oats) is alternated with a strip of cultivated row crop (such as tobacco, cotton, or corn). Rainwater or blown dust from the row-crop strip is trapped as it passes through the subsequent strip of hay plants or grain, thus reducing soil erosion and pollution of waterways. Contour or field strip cropping can reduce soil erosion by 65 to 75 percent on a 3 to 8 percent slope.
Cropping in the strips is usually rotated each year. In a typical four-strip field, each strip will be cultivated with a for one or two years, grain for one year, and row-crop planting for one year. Each strip benefits from one or two years of nitrogen replenishment from nitrogen-fixing cover crops such as alfalfa, and each strip benefits from one year of absorbing nutrient and fertilizer runoff from the adjacent row-crop strip.
Strip widths are determined by the slope of the land: The greater the slope, the narrower the strips. In areas of high wind, the greater the average wind velocity, the narrower the strips. The number of grass or small-grain strips must be equal to or greater than the number of row-cropped strips.
Terraces are often constructed to reduce the slope of agricultural land. To reduce erosion, at least one-half of the land between terrace walls is cultivated with grass or a close-growing crop. Diversion ditches are often used to redirect water from its downhill course across agricultural land. These ditches usually run through permanently grassed strips, through downhill grass waterways constructed across the width of the strips, and through grassed field borders surrounding each field.
Bibliography
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