Big Picture Agriculture

In the Rodale Institute’s 30 year farming systems trial, they found that organic outperforms conventional in years of drought as shown in the photo above. Organic fields increased groundwater recharge and reduced runoff as compared to industrial farming. The organic farm fields had 15 to 20 percent higher water volumes “percolating” through their soils. When rain falls, the organic soils absorb the water instead of running off the surface and taking soil with it. During periods of drought, healthy crop roots can access the stored water present in the organic field soils. And by practicing crop rotation, soil retains more water, reducing erosion and the need for irrigation.

In conservation agriculture or natural farming systems, zero tillage, crop rotations, manure fertilizer, cover crops, and residues help to protect the soil and increase organic matter. During rains, healthy organic soils absorb water and store it better. Good soil structure with macropores allows the water to go deep into the soil where it can be accessed by roots and is less prone to evaporation.

The Nelore cattle breed is of the Zebu species from India and has been raised extensively in Brazil. It does better than most other cattle breeds in conditions of heat, poor range quality, and drought. Its hallmark is the prominent hump behind its neck. Other breeds of the drought tolerant zebu are found in Africa.

In the U.S., the Texas longhorn is gentle, provides lean meat, and is heat and drought-tolerant.

Sheep are very drought tolerant, requiring as little as two gallons of water per day. During the cooler season they require little or no supplemental water beyond their forage intake. Navajo-Churro Sheep are a drought-resistant breed which is tolerant of temperature extremes and can subsist on marginal forage with minimal grain. The Dorper sheep (see photo) is a hardy, popular breed in South Africa. Originating in arid conditions, it is highly adaptable to many environments. Dorper’s have been popular in the U.S. since 1995.

Free range chickens are also efficient meat producers requiring little, but adequate water.

Drought tolerant crops should be consumed in drier regions, such as dried beans, lentils, wheat, millet, and squash. Rainfed or drip irrigated fruit and nut trees produce water efficient food. Some tuber crops and root vegetables are also water efficient.

Much of today’s food transportation system is extremely efficient, allowing for easy trade from the regions that are best suited for growing certain crops. But we need to pay attention to where food comes from when buying at the market, casting an important vote with each dollar spent.

We can save water by taking care to reduce food waste on a personal level. Don’t buy more than you need, store it appropriately, and compost the waste to recycle it into future food.

Thankfully, there is an enormous amount of resilience and adaptability in the human diet.

Biofuel production competes with food production. In the energy-water-food nexus, the IEA (International Energy Agency) predicts that biofuels production will attribute 30 percent of the new demand for water by 2035. It would create the second largest new demand for water, next to coal. (Fracking requires less water than biofuels production.)

The IEA anticipates a 242 percent increase in water consumption for biofuels by 2035. Ethanol and biodiesel now account for more than half of the water consumed for primary fuel production while they only provide less than 3 percent of the energy used to fuel our transportation fleet.

The IEA estimates that corn ethanol uses 4 to 560 gallons of water for every gallon of corn ethanol produced, varying by region. This compares to gasoline which uses .25 to 4 gallons of water per gallon of fuel produced. Furthermore, precious aquifer water should not be permitted to provide irrigation for corn grown for fuel. According to one study, consumptive water use for ethanol production in the U.S. increased 246 percent between 2005 and 2008 and has particularly gone up in the Ogallala Aquifer region. The GAO estimates the average water consumed in corn ethanol production at 324 gallons of water per gallon of ethanol, 88 percent from groundwater.

Wastewater can be recycled and reused for agriculture. Urban wastewater that is treated adequately can be recycled into rivers where it can be reused downstream.

Nations which reclaim the highest percentage of their wastewater include Israel, Spain, Australia, Japan, Middle Eastern nations, Mexico, Latin America, Caribbean, and the U.S. states of Florida and California. Reclaimed water is used for agriculture and irrigation.

Costs for large scale treatment of wastewater are much higher than having available freshwater, even for crops which are not directly consumed by humans. For urban wastewater reuse, the agricultural production needs to be reasonably close to the city providing the water source.

Untreated wastewater is the only option for irrigation in many poor farming regions. Affordable treatment technologies need to become more available to these areas which maximize benefits with the lowest possible risks. Unique and regionally appropriate solutions should be used.

Domestic graywater (laundry, dishwashing and bathing water) can be collected and recycled through a setup of wetlands and aquatic plants which purify it so that it can be used in the garden.

Qanats are old Persian water management systems which draw upon underground water sources, often at the base of mountains. They allow for the creation of a living oasis in the midst of deserts. They are made up of a series of well-like vertical shafts, connected by gently sloping tunnels. Large amounts of water are brought to the surface without pumping by using gravity. Qanats as a water source are nearly as reliable in dry years as in wet years. Qanats allow water to be transported over long distances in hot dry climates with minimal loss of water to evaporation. They are used to provide irrigation in hot, arid and semi-arid climates and many are still in existence today, operating in regions from China across to Morocco.

To learn more about the construction of Qanats and their history, I recommend this site.

(Left) The city of Santa Rosa, California offers a rebate for each gallon of rainwater stored.

(Below) The city of Raleigh, North Carolina worked together with its fire department to set up a rainwater collection and storage system that helps the fire department use less of the city’s drinking water supply.

Some gardeners set up rainwater collection systems which are used to water their vegetable gardens, often employing them in drip irrigation plans.

In addition to harvesting rainwater from roofs, there are methods to harvest rainwater in the soil. The goal is to prevent runoff by encouraging water infiltration into the soil, and then minimizing evaporation. One way to do this is by planting a “rain garden,” which is a collection of shrubs or native plants located in a depressed spot that collects runoff. These collect up to a third more water from roofs, sidewalks, driveways, and lawns that would otherwise enter waterways. Urban rain gardens filter out pollutants to help keep local streams cleaner.

Rainwater may be harvested on a small scale to grow fruit trees, water small livestock, or support fish ponds. The collected water can be stored in small tanks above or below ground, in drums, or in small reservoirs.

On a farm, in situ rain harvesting and filtering are accomplished through having buffer strips, grassy areas, terraces, off-stream storage reservoirs, and natural wetland areas.

Canal irrigation is a surface flooding irrigation method, the most common type of irrigation in the world. Because surface flooding accounts for most irrigation, it is very important to develop and promote methods or technologies which improve the efficiency of canal irrigation.

This is a method of transferring water from a water source to fields. Canals, ditches, basins, furrows, borders, pipes, and surface flooding provide ways to move the water by gravity. Surface flooding can lose more than 50 percent of the water used through evaporation and runoff. Furthermore, soil salinity, loss of nutrients, and runoff pollution can occur. Laser leveling of the land helps improve efficiency.

Seepage from canals or ditches can be reduced by reinforcement of the canal banks and by sealing or lining the canals. Roughly 60 to 80 percent of the water that is lost in unlined canals can be saved through hard-surface lining. Lined canals and ditches may use concrete, concrete blocks, bricks or stone masonry, sand cement, compacted clay, or membranes made of plastic or other materials to line the bottom and sides.

Canal maintenance should be a priority. Inspections are helpful, and keeping the systems weed-free greatly improves their efficiency.

(Note that the top photo, taken here in Colorado, shows a concrete lined ditch with siphon pipes to be placed in furrows for irrigation. The photo on the right, also taken here in Colorado, shows a ditch lined with black plastic.)

Gated Pipes made from aluminum or plastic can be used in the arid West instead of ditch irrigation and they can also be used on laser leveled land. Gated pipes reduce evaporation and leakage, saving 30 to 45 percent of water used, while reducing erosion. The gates can be opened and closed, allowing for watering only the areas, or furrows selected.

The system is set up by delivering water into the pipe using a concrete box containing a tight screen or filter which keeps debris out of the water entering the pipe. Pipes may range from four inches to 15 inches in diameter. Every two feet, the pipe has a plastic slide, or “gate” that can be opened or closed using an irrigating “shovel”.

This is a form of flood irrigation, or gravity irrigation. It is popular in the U.S. and Latin America for growing corn, soybeans, fruits, nuts, vegetables, sugar cane, and pasture land. The cost and operating expenses are comparatively low for this system of irrigation.

Some methods within this category can conserve both water and soil while requiring little capital investment. Terracing, contour bunds, infiltration pits, tillage, integration of tree crops, and green manuring all help to increase water inflitration and storage in the soil.

Bunds: On land with slight or moderate slopes and light to medium weight soils, bunds can be constructed to reduce rainwater runoff, gully formation, and soil loss. Bunds are raised earthen barriers which must be constructed by machine or by hand. They require a significant amount of labor and take a small amount of land out of production. They help rainwater to percolate into the soil. Bunds are used in terraced rice farming to retain water in the paddies.

Half Moons: By constructing half moon structures on slight slopes, rainwater is collected and erosion is stopped. Like bunds, they are appropriate for lighter soils that form surface crusts. They help enable the production of drought resistant crops like millet, where there is little rainfall. Half moons can be used for forage crops in rangeland degraded areas, too.

Terraces: These serve as small dams on sloped farmland and prevent gully washing. While expensive to construct they help preserve soil and water quality and grassy buffer strips provide nesting habitat for wildlife.