Micro Irrigation: How to Make Every Drop Count

 

Mike Wissemann is a tenth generation farmer from Sunderland, MA. His farm, Warner Farm, has been an established source of crops for the surrounding towns since 1718. Mr. Wisseman inherited three hundred years of farming techniques and tricks. He spent his high school years working on the family farm and went on to receive a degree in Plant and Soil Science from the University of Massachusetts Amherst. Mr. Wisseman successfully expanded the farm and his crops from potato/onion crop to a wide variety of fruits and vegetables (Schwarzenbach, 2017). However, no amount of experience or education stopped him from losing tens of thousands of dollars when the Northeast experienced one of its worst droughts in decades (Kaufman, 2016). Farmers all over the Northeast were left scrambling to find enough water for their crops–some were even reduced to bucket brigades to get enough water to their acres of farmland (Shea, 2016).

Despite their best efforts, farmers could not plant their second round of crops. Even generally fertile farm areas such as those by rivers had major problems trying to irrigate (Schwarzenbach, 2017). When your entire livelihood depends on a natural resources (such as water), climate change and increasing drought years are a direct danger to your livelihood.

As climate change continues, droughts like the one experienced by Mr. Wissemann, are going to become more common.  Rising temperatures associated with climate change have impacted approximately 80% of monthly heat records (Coumou, Robinson, & Rahmstorf, 2013). As a rule, as temperature increases, the rate at which an organism produces energy increases as well (Hansen, Smith, & Criddle, 1998). This would be beneficial to productivity, if increased temperatures did not have the additional effect of decreasing the amounts of water available in soil. Think about the application of heat to a pot of water; when the water boils, the water escapes the pot in the form of vapor into the air. The same process holds true when heat is applied to the ground; the water escapes the soil in the form of vapor. This process leaves the soil devoid of water for the plants and leads to drought. The U.S. is a top exporter of agricultural goods and climate change is going to have a significant impact on our agriculture (Joint Economic Committee Democratic Staff, 2012). Between 2000 and 2015, 20-70% of the United States experienced abnormally dry conditions each year (Environmental Protection Agency [EPA], 2016). This does not bode well for the agricultural industry as droughts have an intensely negative impact on crops.

Decreased soil moisture means less water is available for the plants. This both leads to water stress and exacerbates heat stress. Water stress is a variety of plant symptoms that negatively affect plant productivity. It also aggravates heat stress which is when a plant suffers significant tissue damage because of high temperatures or high soil temperatures (Hall, 2017). The same way that humans expect to catch a cold from being overly cold or hungry for too long, plants are more susceptible to disease after being dehydrated and overheated for too long. When leaves of corn are subjected to drought-like conditions, they contained 69% more diseased biomass (Vaughan et al., 2016). When a plant is dehydrated, tiny openings in the leaves close to avoid further loss of water through evaporation. When these openings close, the leaf is incapable of expelling oxygen and taking in carbon dioxide–as if the plant is holding its breath (Osakabe, Osakabe, Shinozaki, & Tran, 2014). Increased heat stress and decreased water availability reduces the plant ability to breathe and thus make food. This results in a weakened plant that is more susceptible to disease (Irmak, 2016; Vaughan et al., 2016).

To get a better sense of the effects of combining heat and water stress, these processes can be related to the human body. Heat stress is similar to running; it elevates your heart rate.  If you run forever without rest, you will pass out, and most likely die without medical attention. Water stress, which is like holding your breath, will also eventually kill you, but can be done for some length of time. When heat stress and water stress occur simultaneously, it is like running a marathon while holding your breath. Such a venture would result in near-immediate loss of consciousness, and death without medical attention. Similarly, a plant under both water and heat stress, sees a drastic decrease in productivity, and eventual death without a change in conditions.

We are exceptionally vulnerable to these effects of climate change on our crops due to our current method of water usage. Current estimates reveal that 70% of freshwater withdrawals go towards irrigation uses (Block, 2017) and a large amount of this water could be conserved. A widely accepted, but inefficient method of irrigation is furrow or gravity irrigation. It accounts for 35% to 42% of irrigation systems in the United States (Subbs, 2016). Compared to a more modern technique known as drip irrigation, it wastes 43.6 % of total water use (Tagar et al., 2012,  p. 792). Furrow irrigation involves planting crops in rows with small trenches running in between them. Water is then flown down the trenches that run alongside the crops (Perlman, 2016). Farmers across the nation use furrow irrigation because there are lower initial investment costs as well as a lower cost for pumping water (Yonts, Eisenhauer, & Varner, 2007). Unfortunately, it also wastes a lot of water. The water is not targeted on the roots and much of it goes to wetting soil around the plant and not the actual root. This is inefficient because the roots are the plant structure that absorb the water (Lamont, Orzolek, Harper, Kime, & Jarrett, 2017). The water that is not on the roots is more likely to be lost as soil evaporation which accounts for over 50% water lost in furrow irrigation (Batchelor, Lovell, & Murata, 1996). Traditional forms of irrigation irrigate the entire field, wasting precious water on soil that will not be in contact with the plant’s roots (Lamont et al., 2017).

Plants need fresh water to survive but, unfortunately, water is a finite resource. Although the water covers 70% of the planet, only 2.5% of it is fresh water. This freshwater is “stored” in places like rivers, lakes, ice, and, perhaps most importantly, in the ground. Surface water seeps down through layers of dirt and rock to recharge groundwater storage areas, more commonly known as aquifers. Aquifers are made up of types of rock particles, such as sand and gravel,  that have enough space between them that the water can happily live. We need freshwater for activities ranging from drinking to manufacturing processes to agricultural irrigation. And about 50% of the freshwater we use for these activities is derived from groundwater (Dimick, 2014).  

The main differing factor between groundwater and surface water as a source of fresh water is the time it takes for these reserves to be recharged. Surface waters, such as lakes, can be replenished with seasonal rains. Groundwater on the other hand can take anywhere from months to tens of thousands of years to build up a reserve because the water has to flow through layers and layers of soil and rock to reach the aquifer. It can also be left untouched for long periods of time as it is not susceptible to the same rules of constant evaporation as surface water.

Agriculture has been using up this resource far faster than it can be replaced. It may take years to build up a water reserve, but it only takes seconds to pump it out. For example, the Ogallala Aquifer, which is located under the Great Plains of the United States, recharges at a rate of less than 1 inch per year (Kromm, 2017). However, over the past decade water has been withdrawn at a rate of approximately 18 inches per year. It is estimated that in the next 50 years, 69% of the Ogallala Aquifer will be gone. This depletion of groundwater resources is happening all over the country from the Colorado River Basin to the California Central Valley to the North China Plain to the Middle East (Dimick, 2014).

We cannot fix climate change, however we can mitigate its effects through effective water usage. Using the method of Micro Irrigation also known as drip irrigation, we can conserve water and mitigate the negative effects of water and heat stress on crops. Micro Irrigation involves using pressurized piping that drips water directly on the roots of the plant. It consists of a mainline distribution, sub-mainline (header), drip lines, filters, pressure regulators, and chemical injectors. Laying down an underground network of pipe which has an opening at the base of each plant. Using a pressurizing system to efficiently deliver water directly to the root system of the plant, which is the part that absorbs water (Lamont et al., 2017).

This decreases the water stress on the plants because it ensures that the plants are receiving enough water. Adequate water leads to healthier and more disease resistant crops (Irmak, 2016; Vaughan et al., 2016).

Not only does this method create better living conditions for the plants, it also conserves an incredible amount of water. This will be especially key as water availability decreases with climate change. Drip irrigation improves efficiency of water on farms by reducing the soil evaporation and drainage losses. In terms of conservation, drip irrigation may require less than half the water needed in a sprinkler irrigation method (Lamont et al., 2017). Since the water is applied directly to the roots, no water is wasted on non-productive areas, resulting in even more water efficiency (Lamont et al., 2017). Drip irrigation was much more efficient than furrow irrigation saving 56.4% of the water in comparison. (Tagar et al., 2012,  p. 792).

However, traditional irrigation wastes water in a way that drip irrigation does not. In terms of the framework of increasing water demand with climate change, agricultural methods that recognize water as a valuable, finite resource need to be implemented.  

Furrow Irrigation is cheaper to install initially, but is far more water and energy inefficient compared to drip irrigation. To install, depending on the type of furrow irrigation and the size of the farm, it will be anywhere from $13 to $70 per acre (Wichelns, Houston, Cone, Zhu, Wilen, 1996). There are more repair costs and maintenance costs for this particular type of irrigation and can be anywhere from $13 to $90 annually per acre (Wilchens et al., 1996). While it is cheaper initially, drip irrigation uses water and energy so much more efficiently, that the long term savings of drip irrigation far outweigh the initial cheapness of the furrow irrigation.

Drip Irrigation costs approximately $500- $1,200 per acre, or potentially more, to install (Simonne et al., 2015). For reference, Louisiana Delta Plantation has over 26,000 acres (Honey Brake Lodge, 2017). An acre is about the size of a football field, which would make that farm the size of 26,000 football fields put together. Even at the lowest cost, converting to Drip Irrigation would cost approximately $13 million for the Louisiana Delta Plantation. Even though the initial investment is hard to grasp in terms of magnitude, eventually the system will pay for itself by maintaining crop yields, even in dry years, and lowering energy and water costs (Stauffer, 2010; Lee Engineering, 2017). How much money will be saved and how many years it will take for the new system to pay for itself is largely dependent on the size of the farm and what kind of crop is being grown, therefore, there are not any specific numbers because of the huge variability of farm types and sizes (Stauffer, 2010). In addition, climate change is very difficult to predict precisely enough for long-term cost analysis, and the type of year-to-year predictions necessary to make those calculations are not presently feasible.

Additionally, the drip method is actually shown to increase crop yields by 22%, which itself is motivation for its implementation (Tagar et al., 2012,  p. 792). California almond farmers have seen their crop yields double as they increased their reliance on the micro irrigation system (Block, 2017). Drip irrigation creates better growing conditions by maintaining the correct moisture conditions favorable for crop growth (Batchelor et al., 1996).

However, if the initial investment cost is offset, micro irrigation will save money in the long run. This method of subsidizing the initial cost has been successful in other situations such as in the case of solar panels. An initial investment cost for switching to solar energy can be anywhere between $10,000 and $50,000 (Maehlum, 2014). It would be reduced by thousands of dollars because of the Federal and state tax credits associated with switching to solar power. Eventually, the solar panels will pay for themselves and even save you money in the long term, much like drip irrigation. Largely dependent on how big the house is, how much power is used, and where the house is located, the payback time for switching can vary, but for an average household with a high regular energy cost would be able to payback the initial investment in as little as 15 years (Maehlum, 2014).

A potential source of funding for this initial cost is the federal government. In a recent publication, the United States Department of Agriculture (USDA) showed that they are willing to fund such advancements in the agricultural industry in the name of invasive species, habitat management, soil erosion, and generalized conservation. Since all these factors contribute to the overall health and wellbeing of a farm, efficient watering is logically a top priority for the government.

These programs fall under The Conservation Reserve Program (CRP) which is a program offered by the USDA Farm Service Agency. The CRP is offered as part of an overall program to address invasive species research, technical assistance, and prevention and control that was set up by the USDA in 2015 (United States Department of Agriculture [USDA], 2015). The CRP specifically is a grant based program where the government is willing to supply money to farmers “for establishment of resource-conserving cover on environmentally sensitive croplands.” (USDA, 2015, p. 4). Among other programs, the Environmental Quality Incentive Program, which gives government aid to farmers who want to use more efficient and conservation friendly tools, and the Conservation Technical Assistance Program, which awards tools for conservation to private, tribal, and non federal lands, show a clear willingness for the government to aid in funding programs geared toward conservation and climate change problems (United States Department of Agriculture, 2015). The method under discussion to more efficiently water our farmland is expensive, but clearly the government is willing and able to encourage and fund conservation of farmlands in whatever way possible, even if that means switching to a more efficient water usage irrigation system.

Currently, despite its ability to conserve water, increase crop yields, and mitigate climate change impacts, the use of micro irrigation is not widespread. This is due in part to its high initial investment cost. With grants from the government to offset the initial costs, the system will eventually save money in the long term. A livelihood for farmers like Mike Wissemann, and food for the public like you, are only going to worsen as temperatures continue to rise. Water efficiency is important now more than ever before.

AUTHORS

Jeremy Brownholtz – Environmental Science

Molly Craft – Natural Resource Conservation

Noah Rak – Building and Construction Technology

Mary Lagunowich – Earth System

 

REFERENCES

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Evan

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