The purpose of this paper is to introduce swale-and-pond irrigation (SPI) as a solution to topsoil erosion and precipitation retention within agricultural systems. After months of research and many sleepless nights, the evidence for agricultural adaptation abounds. Humanity should not hope for continuation with crop failures, increased natural disasters, and a growing global population. A case will be presented that establishes that current practices are causing added stress to our dying ecosystem. This case is meant to prove that current agricultural practices need to be abandoned in order for farmers to continue future crop production. Furthermore the case will demonstrate that SPI is a solution to these failing agricultural practices, as it works with nature to heal the already damaged systems. When SPI is properly implemented its regenerative nature can increase a site’s ability to resist climate issues better than non-adaptive sites. Not only is it regenerative it also becomes a better production system.
Keywords: swale, pond, irrigation, climate change, sustainability, biodiversity, micro-climate
An increase in floods, droughts, fires, and desertification due to climate change is affecting human food security. Intense storms are drowning crops, delaying time-sensitive harvests, and eroding topsoils. Longer dry spells are weakening nature’s ability to resist fires, pests, and pathogens, giving way to barren, unproductive land that once sustained abundant life. Humans either flee their new desert-like habitat to stress another system or stay to live out a bleak existence.
As a species, humans have no known genetic ability to control the weather, but we do have the ability to manipulate our environment to sustain our basic needs. According to an article from History.com (2018) “The Neolithic Revolution started around 10,000 B.C. in the Fertile Crescent, a boomerang-shaped region of the Middle East where humans first took up farming,” beginning with simple tools and limited knowledge the first steps in agriculture were taken. Those first steps have advanced so far, that now most people have no idea how to produce their own crops. Agricultural practices now rely mostly on machinery, chemical soil treatments, and good weather to produce enough food for the ever-growing population.
As the global temperature rises and the weather becomes less predictable, we have to ask ourselves if our current agricultural practices are going to sustain us? The introduction of machines for tilling and chemical applications has led to soil erosion and soil contamination, which we correct with more chemicals and deeper tilling. It is not sustainable yet we continue to produce this way because the demand for food grows yearly with population increases. So, how can we adapt our agricultural practices to fit our changing environment? We need to look back at what has worked for thousands of years, our practices need to become more natural and less disruptive to the environment. Just one of numerous regenerative agriculture techniques is SPI which can dramatically reduce erosion, keep precious topsoil where we need it, retain water, and build our soil fertility in a more natural way.
Diminishing Food Security
The agriculture industry is struggling to meet the needs of consumers as some regions receive less rain than is required for certain crops. Trnka et al (2019) conducted an international study on “severe water scarcity (SWS) and its effects on rain-fed crops particularly wheat, a major human food source. The study concludes that simultaneous (SWS) will increase from the current 15% to 60% by the year 2100.” This will lead to the increasingly growing global population to further food shortages.
Other regions face an overabundance of precipitation and early cold snaps from the changing wind patterns. Laura Reiley (2019) of the Washington Post, reports that “Idaho, North Dakota and Minnesota, as well as the Canadian provinces of Alberta and Manitoba, experienced enough adverse weather from September to November to significantly affect this year’s potato harvest.” Reports like these are becoming far more common in news feeds, and concern more than just the food producers, as its implications affect the entirety of the human race.
SPI is a site-specific design system that harvests rainwater and snowmelt, allowing farmers some control over our second most important basic need, water. Swales themselves are trenches that slow gravitational water as it travels downhill, acting like a small dam, pooling water rather than letting it flow freely away. Swales are built on contour, usually on the sides of hills or slopes. They are dug into the soil at a consistent angle and depth so the swale fills at an even pace and only spills over once the entire swale is full to capacity. Once the swale exceeds capacity, the water flows into another swale, or into ponds for later use.
Ponds are the collection points for water, and, unlike swales, generally retain water indefinitely. Ponds are typically located at the lowest points on any site. However, as we design the SPI we can strategically place ponds at different elevations on-site, which allows ponds to be used to pump water onto crops in times of drought. Both swales and ponds hold water, soaking it into the soil and effectively irrigating the area. With the increased water holding capacity of the soil, trees, shrubs, and groundcovers must be planted to slow erosion and eventually eliminate it altogether as the roots become established.
From the Ground Up
The first step in implementing SPI is site analysis, watching and recording how the water on-site moves and where it goes. This data is crucial for design because it gives the farmer a clear idea of how to utilize the water while still having room for crop production. At the same time, the farmer should take notes on micro-climates across the site. This analysis should not be rushed, each site has different climates. The region may receive little annual rain or it might have heavy snow in winter, time to observe each season may be needed. During this time the farmer should also assess what they intend to produce.
After the analysis is complete the swale can be dug by finding the contour of the slope with a map. The important part of digging the swale is making sure it is consistent across the base, a level is helpful for making sure the whole swale is level. Just like the site analysis, each swale will be site-specific. Digging can be done by hand or machine. All of the excavated soil will be placed downhill from the swale itself and be utilized for planting. To complete the swale, plants will be added to the berm to minimize soil erosion and become a productive part of the system.
PSI and Crop Diversity
Plant species will be chosen that have higher water requirements and functional agricultural use. Swales hosting plants with strong roots that will anchor topsoil in place, and ponds hosting the most aquatic plant species. Together the swales and ponds are a water harvesting, irrigation system, but because they host different plant species they also attract different species of wildlife. This relationship is known as biodiversity, and it includes more than just SPI. Most sites will include field crops such as wheat, potato, corn, etc. and these attract and provide habitat for other forms of wildlife. Some sites include wooded lots or are used for grazing. As biodiversity increases on a site, the system becomes more natural and requires less human input, while at the same time it produces a more diverse selection of food. In addition, ponds can be stocked with fish, swales can host apple, peach, and pear trees.
Established swales produce their own leaf mulch, helping to hold the moisture in the soil longer and return carbon to soil microbes and other soil organisms. Diversity in plant species along the swale will help return a diverse quantity of nutrients to the soil as the leaves drop. Shrubs and groundcovers can be pruned and left on the ground to supplement the leaf litter, a practice known as chop-and-drop. Some might say that this will increase pest populations but actually it balances out because beneficial wildlife also needs a food source.
Because sites have different slopes, soil types, amounts of precipitation, and climates, each site requires a close look during the PSI design process. A swale on the south side of a hill will resist frost and wind damage better than a pond at the base of the north side of the same hill. And that same swale will warm quicker in the spring. These two different areas of the same site are known as a micro-climate. As part of the design process, farmers have to consider micro-climates when designing the PSI system. Micro-climates can increase a crop’s growing season or production, and it can provide habitat that shelters livestock from extreme heat, wind, or cold weather.
Resilience through micro-climate options and biodiversity. The benefits of SPI multiply as the farmer selects and places plants that are resistant to drought, fire, disease, salt, or pollution. Each plant is given its own place on the site and a fire-resistant tree may be used along the property edge, where a neighbor may not be maintaining their property at all. The swales themselves build the resistance of the site to drought and fire by soaking the water into the soil making it more available to tree roots. In times of excessive rain, SPI will channel the water as designed and recharge ponds, possibly beyond capacity but not across field crops or pastures. One of the biggest benefits to resilience is that no matter if it’s a flood, drought, fire, disease, or pollution the biodiversity of the system, should leave the farmer with a harvest of some sort.
The Sad Truth of Our Future
What happens if we don’t implement SPI? Topsoil will continue to erode and contaminated runoff will further pollute freshwater sources. Eric Verso (2015) of Stanford University says, “Soil erosion makes it more difficult for the soil to store water and support plant growth,” gives a little perspective on where we were four years ago, and the progress we’ve had. Time is not in our favor as the global temperature continues to rise, lack of action on our part has pushed us closer to the end of the carbon countdown. Nick Evershed (2017) of The Guardian writes “Our countdown clock shows one estimate of how long it will take to reach an amount of greenhouse gas emissions beyond which 2C of warming will be likely,” the estimate is at 17 years and counting down.
Estimations should be taken with a grain of salt nowadays as researchers such as Jem Bendell author of Deep Adaptation: A Map for Navigating Climate Tragedy and Catherine Ingram author of Facing Extinction both deduce that the window for making significant changes is already closed. Their articles go into great detail about greenhouse gases trapped in the atmosphere and how they will continue to increase the global temperature for years to come. Differing opinions means that critical thinking and independent study is a personal responsibility that everyone should participate in.
Farmers who implement SPI are going to retain topsoil and water on-site allowing them to continue producing even during adverse conditions. The biodiversity will help keep the system healthy and ensures that the farmers don’t have all of their eggs in one basket. Farmers who chose not to adapt are going to continue to see yields decrease as topsoil erodes, precipitation becomes unreliable, and temperatures rise.
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