Soil for Water is a project of the National Center for Appropriate Technology (NCAT), which began in 2015 and is focused on increasing efficiency of water usage on farms of all kinds. The program, which focuses on input from producers in order to share learning experiences farmer-to-farmer, hosts a forum to encourage innovation.
The program is free and voluntary, and features events, technical assistance and the website hosts an online map (“The Regenerator’s Atlas of America”) of those farmers who want to identify their operations as being regenerative and share their story of enhancing water usage.
Mike Morris, NCAT Southwest regional director and director of the Soil for Water Project, explained that while information on irrigation and water management for crops often focuses on the technical aspects of getting water to the crops, soil health is also a major factor.
Increasing the water carrying capacity of soil is the “new angle” in irrigation, Morris said. “Soil health has a lot of relevance to drought. It (soil health) can be one of the most effective things people can do on their own place to cope with dry times and low water availability.”
With increasing periods of extreme drought, the drying up of aquifers across the U.S. and the fights over water rights, utilizing available water efficiently and effectively for crop yield and quality is going to be of growing importance. Morris and fellow NCAT Specialist Katherine Favor addressed irrigation efficiency in relation to soil health in a recent NCAT podcast.
Soil Health Impacts on Water
“When we create a healthy soil structure, it can capture and hold more water,” Favor said. Soil microbes release exudates which hold soil together, creating a “fluffy” tilth with porous spaces which can hold water.
“Connecting soil biology to irrigation” is the link that has been missing in much of the discussion of irrigation management, Morris said. As soil health increases, “everything in irrigation gets easier.”
As water is better able to infiltrate the soil, and the soil is better able to store that water, the greater the efficiency of any irrigation strategy, as less irrigation will be needed. Decreasing soil compaction through low- or no-till farming, and leaving living roots in the soil with cover crops, enhances water infiltration creates channels in the soil, allowing water to flow. Mulching the soil via leaf litter, crop residues or cover crops also helps to keep the water in the soil.
And as soil organic matter increases, so does plant available water, Favor said. Although it’s hard to quantify the relationship between the two, as soil type and other variables factor into the equation.
Irrigation doesn’t have to be high-tech to work efficiently. There are systems that fit every farm. But no matter what technique is utilized, farmers need to know where their soil is now and how it compares to heavy, compacted soils. The goal is to enhance soil health year-to-year, which will increase irrigation efficiency, Favor said.
Farmers can easily measure soil water infiltration by using a shovel or a push rod, digging or pushing it into the ground to determine how deep the water is actually penetrating into the soil. A ring test, performed by placing a metal ring in the soil, then filling it with water, to observe how long it takes the water to fully filter down is another low-cost way to monitor water infiltration.
Tensiometers are a low-cost technology and measure soil water tension, which correlates with soil-water content. Neutron probes are high-tech (and high cost) and are typically used with high-value crops to determine the soil moisture content.
“These tools are out there. There’s really something for everyone,” Favor said. “Just start monitoring at some level.”
While the crop’s rate of water use depends upon evapotranspiration, which changes with the temperature, humidity and the particular crop being grown, getting the correct amount of water to the crop at the right time will increase yield and quality while decreasing water usage. As plants evapotranspire, water from the soil is pulled up through their vascular system, depleting soil moisture. Adding back the amount of water that the crop is actually taking up is the key to efficient irrigation.
Micro or drip irrigation systems, often considered the most efficient systems, deliver water directly to the plant’s root zone, eliminating waste. But they can be expensive to install, emitters can become clogged and emitters need constant monitoring to ensure they’re all delivering the same amount of water uniformly to the crop. Efficiency drops quickly if the system is not maintained properly.
Microbes in the soil need water too. Drip irrigation concentrates water in one spot, which could leave soil microbes outside that zone without adequate water, which may be a drawback to micro irrigation, Favor said.
Sprinkler systems, pivot systems and flood irrigation can all be done effectively and efficiently. Morris noted that those using pivot systems often under-irrigate the crop, however.
“When you start to monitor your soils, you can really have it on the exact amount of water your crop is needing,” Morris said, no matter which type of irrigation system is used.
Whatever way you apply irrigation water, it’s essential to maintain equipment, monitor soil health, know how much water is being applied and know how much water the crops being grown actually need, Morris said.
Awareness of the role soil health – which encompasses soil microbiology, soil physical and chemical properties, and which influences and is influenced by the interaction of plants with the soil – is known to play a significant role in managing the amount of water needed to grow a healthy, high-quality and high-yielding crop.
Soil health factors into the equation when optimizing irrigation efficiency, while enhancing soil health leads to more efficient water usage and decreases the need for irrigation.
NCAT has updated publications on irrigation available at attra.ncat.org/?s=irrigation&post_type=attrapub.
by Tamara Scully