Farming is one of the oldest and sustainable human activities. As societies evolved from simple to sophisticated lifestyles, human beings began to till land and farm in order to produce their own food. As time passed, man discovered different ways of tilling and farming on different landscapes, including slopes that are notorious for soil erosion. Some of the methods used to date include windbreaks, planting cover crops, planting grass on waterways, and contour cultivation among others. Contour cultivation (contour farming, contour plowing, or contour bunding) is a sustainable way of farming where farmers plant crops across or perpendicular to slopes to follow the contours of a slope of a field. This arrangement of plants breaks up the flow of water and makes it harder for soil erosion to occur.
How Does Contour Farming Work?
Plowing and planting across slope contours create man-made water breaks that not only allows enough time for the water to enter the soil, but also to settles the topsoil without washing it down the slope. On slopes with no contours, water runoff quickly without the soil properly absorbing it and carrying the top fertile soil with it, therefore, leaving a non-fertile land up the slope. Contour farming also creates water breaks that reduce the formation of gullies and rills when a place experiences heavy rains and water run-off which is the leading cause of soil erosion. For contour farming to be effective, the resulting curved furrows around the slope ought to be on equal levels. Contour farming can have one crop on the farm or a mixture of several crops through strip cropping.
What Is Strip Cropping?
Strip cropping is a type of contour farming where farmers plant different crops in alternating strips of different levels. This method equally prevents soil erosion and can improve soil fertility through crop rotation. For example, a farmer may plant different crops on different strips of land during alternating farming seasons, such as rotating strips of legumes and corn enables the corn to use nitrogen that the legumes left in the soil.
Benefits of Contour Plowing
First, contour farming maintains soil fertility by preventing downwash of the fertile topsoil of a farm and consequently enabling betters yields. When done right, this method reduces erosion by more than 50%. With the reduced loss of fertility comes the reduced use of fertilizer and a reduced cost of purchasing fertilizers. In most cases, rainwater washes farming fertilizers downstream and consequently contaminating freshwater systems. Secondly, contour plowing increases the soil’s water retention ability to ensure that enough water soaks into the soil for good health of the plants. Furthermore, water retention improves soil quality, irrigation, and water conservation thus reducing labor that would have gone into physical fetching of water. Other benefits are and time efficiency and reduced use of machines which in turn reduce the wear and tear. In summary, the method tends to promote sustainable agriculture and reduce most of the ills associated with soil erosion on slopes such as habitat destruction.
Early Origins of Contour Farming
During the period of Ancient Greek, a thalassocratic ancient Semitic civilization, the Phoenicians, who originated from the Eastern Mediterranean, practiced some of the earliest forms of contour farming. The farmers in Phoenicia (land of the palm trees) helped spread contour farming throughout the Mediterranean region and eventually many farmers in present-day Israel, Lebanon, Syria, Gaza, and parts of Turkey adopted the method, however, the Romans at the time preferred straight furrows. Over a period, societies who embraced irrigation farming adopted this method of plowing and planting. This practice eventually spread to different parts of Europe who also introduced contour farming to some of their colonies. The first ever recorded contour farming in the US came at the turn of the nineteenth century but the country did not fully embrace this method until during the twentieth century. During the time of Thomas Jefferson’s term, farmers called this system “horizontal plowing” and his relative, Randolph, developed a plowing technique that caught water in ridges of upturned land unlike plowing down like roof shingles. Randolph’s invention amazed Jefferson because of improved water retention capability. This method did not really take off during this time because farmers had little knowledge on erosion.
Modern History of Contour Farming in the US
In a bid to control soil erosion, the US Department of Agriculture established the US Soil Conservation Service, currently the Natural Resource Conservation Service, and started promoting contouring in the 1930s. This move was after a realization that soil erosion, just like desertification, was a threat to agricultural sustainability in the US. In 1934, the Yearbook of Agriculture wrote that “more than 35 million acres of previously cultivated fertile land were destroyed and could no longer yield enough crops.” Furthermore, the book also noted that 100 million acres of the then cultivated land had lost most or all of the topsoils that contained humus and over 125 million acres of the then cultivated land were losing their topsoil in an alarming rate. The consequences of that trend, according to the yearbook, could have been large-scale desertification and permanent transformation of the agricultural landscape to an arid area. In addition, the book noted that the trend had other consequences including, low food supply, massive loss of jobs and properties, and increased commodity prices.
To roll out a massive campaign for contour farming, the Soil Conservation Service partnered with federal institutions, state governments, universities, and communities in order to promote the method to both small-scale and large-scale farmers as well as to research more on how to achieve the best results with the method. Institutions such as the University of Nebraska rolled out innovative campaigns that challenged farmer perceptions and encouraged them to do contour farming. Within the next four years, the new agricultural techniques reduced soil erosion by approximately 65% although drought prevailed. Most farmers reported between 5% and 10% increase in yields although demonstrations under ideal conditions indicated that the yield can increase by wider margins of up to 50%. As the campaign had anticipated, farmers reported using less fertilizer, reduced erosion, and less energy and resource use.
Ideal Places and Conditions For Contour Farming
The practice of contour farming, though good, is not ideal in all slope and climate conditions. Contour farming is effective on slopes that have gradients between 2% and 10%. Secondly, the area must be receiving a given amount of rainfall in a given period. When the slopes are steeper and rainfall is greater, strip cropping becomes ideal in contour farming because this provides an extra layer of protection.
Experts encourage contour farmers to use additional soil and water conservation techniques to supplement the former in order to yield the best results. Such supplements include strip cropping, use of cover crops, use of windbreaks, grassing waterways, and building terraces among others. Strip cropping is good for long and steeper slopes while irregular slopes need more than a single key contour line. In getting the key line, farmers should use a contour gauge or a hand level and thereafter plant parallel to the key line. Grassed waterways are also important, especially where there is a high concentration of runoff water while grassed strips come in handy where the contour lines are too sharp for farming equipment to plow. Other techniques to include are growing bush or tree borders across the slopes (vegetative barriers), residue management, and mulching to protect the soil.
What Is the Keyline Design?
To better understand the ideal combination of techniques, farmers should have in mind the climate of the region, soil condition, and the angle of the slope. An agricultural land fall under one of the following classifications; extreme, high, moderate, mild, or insensitive in terms of soil sensitivity. P.A. Yeoman devised the Keyline Design that guides contour farming in order to get some minimum ideals.
The Keyline Design looks at how specific topographies link to water flow for an optimum use of water on a farm. In the design, contours ought to be made in specific ways to control rainfall runoff and maximize irrigation of undulating land during fast floods without building terraces. This system also observes that at the end of a contour, the land is always steeper on one side than the other leading to furrows deviating from the true contour when plowing parallel to a contour, thus making rainwater flow to the steeper side and increase erosion. To control this movement of rainwater, Keyline Design uses “off contour” drift when tilling furrows.
Planning ahead helps the seemingly difficult contour farming to become easy. Planning involves surveying and estimating the number of contour lines needed and if other methods would be necessary to supplement. For effective yield, farmers should perform regular check and maintenance. Maintenance rectifies unforeseen mistakes as well as repair areas that elements of nature destroyed.
Contour Farming Across the Globe
Contour farming is popular on all the inhabited continents of the world. In many countries, both small-scale subsistence farmers and largescale farmers try to overcome slopes through this method. In North America, both the US and Canada have extensive farms under contour farming. International organizations such as Oxfam UK and FAO encourage farmers in parts of Africa like Burkina Faso to adopt contour farming.