On October 2, 2019 Mr. James ADKINS spoke to us on irrigation practices across the state of Delaware and how they’ve evolved over time. Mr. ADKINS has a Bachelors degree from the University of Maryland and works at the UD Carvel Research Center and is an Extension Specialist with fruits and vegetables. He also worked with Mr. KEE- the man who brought PictSweet to Delaware along with mechanized pickling. Additionally, Mr. ADKINS works with equipment, technology, and irrigation nationally and internally, as well as handling irrigation on Warrington Farm.
The talk began with a brief history on irrigation in relation to the systems used today. Only 20% of the world’s farmland is irrigated but 40% of the world’s food supply is produced with irrigation. Mr. ADKINS traces irrigations humble beginnings to the Towers of Babylon in Machu Picchu, originally pumped by slaves. Irrigation systems requiring man-power could be found in other ancient civilization throughout the world, as well as animal, wind, and water power.
One of the first methods of irrigation Mr. ADKINS discussed was flood irrigation. Also called gravity/furrow irrigation, it is used when a weir controls the water flow. This type of irrigations works best on heavy (capable of holding a lot of water), mostly level soil where 3-4inches of water is applied per application- Delaware is not level enough to employ this method. In California, however, each farm receives this type of water delivery method 4 times per year with a 4 inch application each time. Siphon tubes are used to run water across a ditch with grated pipe, a system used by 30% of U.S. farms. A canal manager/operator oversees the transfer of water between farms as farmers upstream receive the water, then that tailwater is re-used on the next farm down. Mr. ADKINS tells us that there are stockholders in canal water- reiterating the points made by Mr. KEE about the complicated water rights in California. The Homestead Act and combined with the controversy around who owns what means farmers may not even own the water underneath their property.
After WW2 came the advent of the pressurized sprinkler system. With this system came the second method of irrigation, using hand-moved pipe. This pipe was made from aluminum, originally sourced from scrapyards in Washington and Oregon where airplane manufacture had been done. This system was often used in the western U.S. A variation of this system, side-roll wheeled-pipe, could be hooked to 150-200ft risers underground and can be seen in use in Idaho. This system doesn’t work well with corn.
Another pressurized system, the traveling gun, can be used for corn, soybeans, wheat, and other agronomic crops. This device has the spraying power of 10-20 fire hose in pounds per square inch (psi) of pressure. This force is not evenly applied, however, and the machine itself requires lots of power and fuel, meaning it has negative energy efficiency. This device is often used on sports fields, running 6hours at a time to cover 10acres. It is a poor choice to give water to newly plant, fragile, and shallow rooted crops.
Frank ZYBACH’s center pivot irrigation, uses an anemometer powered by water. The crops it is used on are often planted in circles. Mr. ADKINS showed us examples of it’s use in Nebraska, but it is broadly used, even in largely desert countries like Saudi Arabia. The system is used in Delaware and works well with furrow planted crops.
The greatest percentage of irrigated land exists in Asia, where 68% of the farmland receives water via surface water irrigation like dams and hydroelectric. Half of the 60 million acres of U.S. farmland that are irrigated use flood (surface water) irrigation. Mr. ADKINS informed the class that the first source of irrigation is often surface water before acquirers are sourced for water instead- aquifers require more pressure to pump water and therefore more money. Most of the irrigated farms in Asia are small, encompassing less than 5acres. 90% of India’s freshwater is used for agricultural irrigation compared to 65% of China’s freshwater.
After Asia, America comes in at a mere 17% with it’s irrigated farmland, followed by Europe at 9%, Africa at 5%m and Oceana at 1%. The U.S.’s irrigated farm area expanded rapidly from 1950 to 2000, going from 250 acres to 700 acres, or 280% in 50years. This is staggering, compared to the 10% increase from 2000 to 2010. Despite the more modern methods of irrigation utilized in the U.S., many aquifers are struggling. An example would be the large Oklahoma state high plains aquifer that is being depleted faster than it can naturally recharge- the rivers going through aren’t given the chance to percolate. Globally 15-35% of irrigation withdrawals are projected to be unsustainable. In California, irrigation withdrawals were a mere 19% in 2005, with almond trees allowed to die as irrigation water is diverted to the city for people to drink instead.
In Delaware, 30% of the farmland, or 15, 000 acres is irrigated. In Sussex County Delaware, 50% of the farmland is irrigated. In the older properties of the county, many wells are hand-dug and only go as deep as 40ft, when modern wells are often much deeper. Controversy often arises from citizens believing the neighboring farms center-pivot system is pumping out their drinking water, however this is often incorrect as domestic-use wells are deeper than irrigation wells and often tap into different aquifers because the aquifers are ‘stacked’ underground. Companies like Tidewater and Artesian can capitalize on these water disputes by promising new residents in their brand new developments, ‘fresh, uncontaminated drinking water’. When consumers buy a property they purchase water allocation rights, meaning the cone of influence to off-set their neighbor can’t exceed a foot of their well water.
Irrigation can also give locales on brink of disaster a second chance. In Ken BURNS’ documentary, ‘The Dust Bowl’ an Oklahoma city is irrigated after a lack of rainfall due to climactic change and the farmland is able to be recovered. In Saudi Arabia, 16, 000ft. well are dug to pump acquirers in the desert and increase the countries food security in times of conflict. Water desalinating technology is another expensive method used to bring water to the desert.
Lastly, Mr. ADKINS discussed ways in which aquifers are made more effective and efficient. 1 million gallons of water usage equals 10 households per year, 1.5 Olympic swimming pools, and 100 acres of corn in 1 day during the pollination stage. Much of the water applied to crops can be lost to the soil and air in a process referred to as evapotranspiration,or ET. Mr. ADKINS showed us an image of an old dike system where the aquifer was lined with concrete to prevent water loss from water seeping through the salt rock. He shared an interesting anecdote in which, through his travels, he learned that Idaho kids can ride a raft down the river for 20miles to an overpass for recreation. Certain cultivars, like corn, can use copious amounts of water- anywhere from 20-25inches, or an average of 22 in per year. Crop coefficients can be measured and estimated based on crop and growth stage charts and taking variables like humidity, rainfall, and wind into consideration. Increasingly high temperatures can make irrigation even less effective, as water is lost when plants are under heat stress. In Delaware, the sprinkler, drip, and sub-surface irrigation may require more water usage in sandy soil, but still used less water overall that alternative methods. In New Castle County, specific methods like drip irrigation can be better for the general soil type.
New irrigation technology was shown briefly at the end of the lecture. The Warrington Pivot works via SmartPhone and can be turned on remotely, creating added convenience and reducing the need for travel for farmers. When using the corner system and center pivot, zone control can be employed to adjust the water distribution rates for varying soil types on different plots of land- also known as Variable rate irrigation, or VRI, a small system for an area f low variability can cost $25, 000 as opposed to upwards of $30-$40, 000 for a larger, more complex system. To justify the expense, farmers use a free AGIS soil survey with records dating back to the 1940s to determine the needs of their property. For additional support, farmers can seek the help of a Natural Resource Conservation Specialist. Major soil variability will often occur near rivers and swamps, but any equipment for slight variability is usually used as a research tool, instead of a practical farming expense.
As the lecture lasted right up to the end of class, there was little in the way of closing statements or remarks.