I’m a big fan of topography maps, the lay of the land as seen from above, of geological shapes, patterns, of colors of the terrain in the landscape. It is no surprise that I love the patterns made by farming and in particular ones that use the Center Pivot Irrigation system to irrigate the fields. Perhaps it is the random quality of the patterns, the pace, the line breaks, and the unexpected end revelations.
The center pivot irrigation systems is said to be the most significant mechanical innovation in agriculture since the replacement of draft animals by the tractor. In many states like Nebraska, where rainfall is unpredictable, 7.6 million acres are under this irrigation method.
From above, the fields roll out in an quilt of circles and squares. An efficient grid of crops without sight of trees. What have we learned from our past, where is the older agricultural practice of planting trees as "shelter belts" along with food crops? I was taught that trees reduce evaporation from soil and transpiration from crops while reducing wind erosion...
One of the drawbacks of center pivot systems was that the circles of well-irrigated land they produce are usually forced to fit into a square system of land parcels and roads. When the first pivot systems were being installed in the 1950s and 60s, most farmers were working quarter-of-a-mile sections of 160 acres. The center pivot systems were able to reach only 133 acres of that "quarter," and the corners inevitably produced poor crop yields.
One way to solve the problem of wasted land is to buy enough land to break the square pattern of land distribution and install the circles in a hexagonal pattern that minimizes the space between circles. This approach was used in the 1960s in Libya, but it doesn't work very well in most of the U.S. where land is already divided into square and rectangle parcels.
Some farmers tried to solve the problem by planting more drought-resistant crops on the corners. The main field would typically be planted in corn and the corners planted in milo. But those different crops have different water, chemical and harvesting needs, so it was an imperfect solution (herbicides, fungicides, and pesticides are chemigated through the pivot system).
Thoughts from a 747 window over Western USA
If I can’t train my eyes to love, how else can I praise the farmers who shape the land, a tessellated blanket of parched hope and tired soil.
A crop circle in the Saudi Arabian desert. An installed quarter-mile-long center pivot system costs about $70,000 to $120,000 on average. The pivot’s speed is adjustable. It takes 36 hours to make a full circle on 167 acres, putting down a half-inch of water.
The majority of our food is made up of the same genetically-modified crops, just four crops — corn, rice, soybeans and wheat. The irony is that this harvest is not eaten, directly, it is milled and processed into flours or starches, or used to fatten animals on feedlots. Washington determines how our farmers farm. They do it through the farm bill, a mammoth piece of legislation that designates American agricultural policy every five years. It’s really a FOOD and Farm bill, a sweeping bill in every sense — nutrition, conservation, genetic engineering, food safety, school lunch programs, water quality, organic farming...
Resembling a work of modern art, variegated green crop circles cover what was once shortgrass prairie in southwestern Kansas. Corn, wheat, sorghum, each of these crops is at a different point of development, accounting for the varying shades of green and yellow. Healthy, growing crops are green. Corn would be growing into leafy stalks by late June. Sorghum, which resembles corn, grows more slowly and would be much smaller and paler. Wheat is a brilliant gold and the fields of brown have been recently harvested and plowed under or lie fallow for the year.
I see our extraordinary stamp of on nature. I think of language, I hear music – whose rhythms are fragile –
the pattern is percussive, a score, a chart, a test, a work of architecture…
Agricultural fields south-west of Perdizes, Brazil. Central pivot irrigation draws water out of a single well in the center of the field. Long pipes perched on wheels rotate around the pivot, showering the crops with water. Because the water falls directly on the crops instead of being shot into the air as occurs with traditional sprinklers, less water is lost to evaporation and more goes to nourishing the growing plants.
Central pivot irrigation also creates perfectly circular fields. The larger fields shown here in Colorado are 800 and 1,600 meters (0.5 and 1 mile) in diameter.
The Wadi As-Sirhan Basin in Saudi Arabia. For scale, the agricultural fields in the images are about one kilometer (0.62 miles) across.
The thirsty plants that rise out of the Arabian desert are quenched by water that dates back to the last Ice Age. In a more temperate past about 20,000 years ago, this “fossil” water filled aquifers that are now buried deep under the sand seas and limestone formations. Saudi Arabians have reached this underground water source by drilling wells through sedimentary rock, as much as a kilometer beneath the desert sands.
Although no one knows how much water lies beneath the desert—estimates range from 252 to 870 cubic kilometers—hydrologists believe it will only be economical to pump it for about 50 years. Rainfall averages just 100 to 200 millimeters per year and usually does not recharge the underground aquifers, making the groundwater a non-renewable source.
In 1953 while drilling for oil in southern Libya, workers found instead a huge freshwater sea beneath the sands, a vast ocean called the Nubian Sandstone Aquifer System which stretches beneath Libya, Egypt, Chad and Sudan. The water had accumulated during the last ice age. Its reserves are estimated to be the equivalent to about 500 years of Nile River flow and are expected to last a thousand years.
Near Santa Cruz, Bolivia, the radial-pattern fields are part of a planned settlement scheme in a rainforest area. At the centre of each unit is a small community, which is surrounded by fields. A small buffer of forest separates the settlements from one another.
South of Khartoum, Sudan, where the White and Blue Nile rivers join, a dizzying arrangement of irrigated fields stretches out across the state of El Gezira. Given the semi-arid climate of the surrounding area, this geometrical spectacle of fertile green fields depends on thousands of miles of canals and ditches that connect the region to the Blue Nile in the west. The man-made rivers and streams are part of an irrigation project called the Gezira scheme, which the British started in the colonial era to grow cotton for export back to Europe.
The Orange River between the border between Namibia and the Republic of South Africa. Along the banks of this river, irrigation projects take advantage of water from the river and soils from the floodplains to grow produce, turning parts of a normally earth-toned landscape emerald green. A network of bright rectangles of varying shades of green contrasts with surroundings of gray, beige, tan, and rust. Faint beige circles reveal center-pivot irrigation fields apparently allowed to go fallow.