A Personal Relationship

Water and Soil

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All agriculture is dependent on the availability of nutrient-rich soil and an adequate supply of water. The climate on the western Great Plains is characterized by a rate of evapotranspiration (water loss from soil and plants) that exceeds the rate of rainfall during critical stages in the growing season. This semi-arid (a semi-arid area or climate (general type of weather) has little rain but is not completely dry) region is marked by warm, dry summers and recurrent droughts where rainfall is on average less than 30 inches per year—well below the amount needed to grow most crops. Yet, the Platte River Valley is one of the most productive feed-grain regions in North America.

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Water

“Crops don't grow without water. I have the responsibility to be a good steward and be conservation minded when it comes to how I utilize and consume water. It isn't just about quantity of water now; it's about quality and timing.” —Roric Paulman

This scenic Nebraska river is a source of surface water for nearby farmers.
This scenic Nebraska river is a source of surface water for nearby farmers.

A combination of unique geological features and human ingenuity make it possible to grow crops like corn and soybeans on the Great Plains. Without adequate rainfall, farmers in the Platte River Valley depend on both the North and South Platte rivers to irrigate their crops with surface water. The rivers’ headwaters begin high in the Rocky Mountains of Wyoming and Colorado at elevations of 8,000 to 10,000 feet and are recharged annually by snowmelt. To supplement surface waters (Water on the surface of the planet such as in a river, lake, wetland, or ocean.) from the rivers, farmers also rely on groundwater (Water that collects or flows beneath the Earth's surface, filling the porous spaces in soil, sediment, and rocks.) from the High Plains Aquifer, also known as the Ogallala Aquifer, pumped to the surface by center pivot systems.

The Platte River and the underlying Ogallala Aquifer (a shallow water table aquifer surrounded by sand, silt, clay, and gravel located beneath the Great Plains in the United States) are important sources of water in this distinctive agricultural region within the Great Plains. After the Homestead Act (The Homestead Act opened up settlement in the western United States, allowing any American, including freed slaves, to put in a claim for up to 160 free acres of federal land.) attracted farmers to the Platte River Valley, it was not long before they discovered that the river was not a reliable source of irrigation during the summer months. Wells and windmills were only a temporary solution as more than one million people settled on nearly 375,000 farms across Nebraska by 1890. Citizens in western Nebraska determined that they would have to work together to bring an adequate supply of water to their cropland and founded the Farmers Irrigation Project. They successfully diverted water from the North Platte River with more than ten miles of hand-dug ditches. But still this wasn’t enough to sustain their expanding crops and the massive undertaking soon overwhelmed them. The federal government offered relief with the passage of the 1902 Reclamation Act, which initiated the Sweetwater Project that would build Pathfinder Dam in Wyoming and deliver—through a massive canal system (human-made channels, or artificial waterways, for water)—enough water to irrigate 150,000 acres in western Nebraska.

Diagram of the HIgh Plains Aquifer.
Diagram of the HIgh Plains Aquifer.

The region relied heavily on surface waters from the Platte rivers until 1897 when N. H. Darton, a government geologist digging wells near the town of Ogallala discovered an extensive aquifer. Darton named his find the Ogallala Aquifer, but we now know that he had found one part of a larger aquifer (a body of permeable rock which can contain or transmit groundwater) system, the High Plains Aquifer, which extends from the Texas Panhandle, into New Mexico, Oklahoma, Colorado, Kansas, Wyoming, Nebraska, and South Dakota. This vast groundwater (Water that collects or flows beneath the Earth's surface, filling the porous spaces in soil, sediment, and rocks.) source could be accessed with wells and pumped to the surface with windmills, but each well provided only enough water to irrigate 5 acres or provide enough water for 30 cattle.

It wasn’t until 1948 that a dryland (characterized by a scarcity of water, which affects both natural and managed ecosystems) wheat farmer in Colorado named Frank Zybach found a way to make use of the aquifer. Zybach, who was originally from Columbus, Nebraska, invented center-pivot irrigation (a method of crop irrigation in which equipment rotates around a pivot and crops are watered with sprinklers) and together with Robert B. Daugherty, the owner of Valley Manufacturing, developed a lasting technology to draw irrigation water from the Ogallala Aquifer. By the 1970s, the Great Plains had more than 48,000 center pivots that irrigated more than 20 million acres of cropland. If you’ve ever looked out your airplane window and seen green, brown, and yellow circles of various sizes dotting the landscape, you’ve seen center pivot irrigation from a bird’s-eye view. A fixed four-legged pivot tower draws groundwater from a well at the center of a crop field and then pumps it through to a long, wheeled sprinkler system that rotates around the field, watering the crop. The drive systems were originally powered by water, but today are powered by electric, oil-hydraulic, and solar power.

A crop field using center pivot irrigation, from above.
A crop field using center pivot irrigation, from above.
The center pivot accelerator is the water's exit nozzle.
The center pivot accelerator is the water's exit nozzle.

Since the 1990s, smart irrigation systems, using computerized controls, monitor soil moisture to deliver varying and precise amounts of water. Roric Paulman measures soil moisture with sensors called capacitance (the ability of a system to store an electric charge.) probes that are buried in the fields. The probes indicate the moisture levels at 4, 8, 12, 24, 36, and 42 inches below the ground. Roric can monitor the system without being in the field. “We get a report of that to our phones in real time,” he said. “We know exactly what’s going on underneath this pivot.” Watering crops is expensive, so it’s important for farmers to apply just the right amount to be profitable and to conserve resources. Given that some states regulate how much water landowners can pump for crop irrigation, farmers must develop an irrigation schedule to make sure that the plants are receiving the right amount of water at the right time. It is important to apply water at critical growth stages to avoid stressing crops

Plants use water for growth and cooling purposes. The plant’s vascular system (The conducting tissues and supporting fibers of a plant.) absorbs available water at the root zone through the root system. As water moves through the plant from the roots up to the leaves, it is transported to the underside of leaves where it evaporates and is released into the atmosphere through a process called transpiration. To determine the correct amount of water to apply to crops, farmers must also take into consideration water that evaporates from the soil through the inefficiencies of the irrigation system. The effects of water loss from plants and soil is known as the evapotranspiration (The combined processes of evaporation, sublimation, and transpiration of water from Earth’s oceans and lands to the atmosphere.) process. Evapotranspiration rates change over a growing season. When crops are small, evapotranspiration is low. As the growing season progresses, the leaf area expands and evapotranspiration rates increase until they meet atmospheric demand, or the atmosphere’s thirst for water. Just how thirsty is the atmosphere? That depends on temperature, humidity, wind, and solar radiation (Radiant energy emitted by the sun from a nuclear fusion reaction that creates electromagnetic energy.). Calculating atmospheric (relating to the atmosphere of the earth or (occasionally) another planet. "atmospheric conditions such as fog, snow, rain") demand helps farmers limit crop stress, conserve water resources, and maximize yield.

Modern farmers, like the Paulmans, also inject aqueous (Of or containing water, typically as a solvent or medium.) chemical inputs, such as herbicides (A substance that is toxic to plants and is used to destroy unwanted vegetation.), fungicides (A chemical that destroys fungus.), and insecticides (A substance used for destroying insects or other organisms harmful to cultivated plants or to animals.) (chemigation), and fertilizers (fertigation) into the center pivot system for more efficient application. Roric uses fertigation ( the injection of chemicals into an irrigation system) to help precisely meet the demands of his crops and avoid over application, “When we soil test, or when we make these zone prescriptions, we basically spoon feed the crop, whether it's corn, whether it's edible beans, whether it's popcorn. We basically just feed it what it needs. It would be similar to a nursery or a greenhouse.” Roric monitors the system with computers, and even an app on his cell phone, to program and make adjustments to inputs in real time.

Closeup of a center pivot head.
Closeup of a center pivot head.

The precise application of water and chemicals controls the volume and frequency of application, which makes it possible to meet crop needs while preventing soil and water quality problems such as soil erosion, salinity (The salt level of water.), and the leaching of nutrients or chemicals.

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Soil

“The soil is the foundation of any farm.”—Roric Paulman

Today, modern farmers understand that healthy soils grow healthy crops. Not all soils are the same, there are several soil types found on the Great Plains. Their physical characteristics range from sandy soils to dark, fertile soils rich in organic matter (matter that contains a large amount of carbon-based compounds or dead matter). Minerals, nutrients, organic matter, and microbiological (The study of microorganisms, which are unicellular or cell-cluster microscopic organisms.) diversity strengthen soil structure and help grow a range of foods. No-till farming, crop diversity, cover crops, and crop rotation are important best farming practices that help maintain healthy soils. Roric does not till his land as his father and grandfather once did. “We try to plant right back in that residue and disturb as little as we can,” Roric says, “so that we can maintain the integrity of all the organic matter that’s out there.” After the crops are harvested, the remaining corn stubble (the short stalks which are left standing in fields after corn or wheat has been cut) and organic matter are left on the fields to hold in moisture and protect and enrich the topsoil. Microbes (A microscopic organism which can be single-celled or a small colony of cells.) and invertebrate (An animal without a spinal column or backbone.) animals help break down the organic matter into available nutrients that will help next season’s crops grow.

Closeup of soil and roots.
Closeup of soil and roots.

“There’s biological activity in these fields,” explains Roric. “There’s earthworms and all kinds of good microbes feeding on the organic matter, and so you mix that in the soil and that makes the soil nutrient-rich. We value the residue, the corn stalks, and the shucks (an outer covering such as a husk or pod, especially the husk of an ear of corn), and the leaves, and the tassels.

Illustration showing soil bugs and microbes.
Illustration showing soil bugs and microbes.

We value that as a cover to keep down that soil erosion from wind or from evaporation on a hot summer day.” To maintain active and diverse microbiological communities that support productivity and sustain a healthy agricultural ecosystem, modern farmers manage crop residue, practice no-till crop production (also called zero tillage or direct drilling, is a way of growing crops or pasture from year to year without disturbing the soil through tillage), and maintain cover crops.

Components to good soil.
Components to good soil.

The residue, or organic matter, left in the field after a crop is harvested protects the soil from wind and water erosion, and evaporation. Paul Jasa, Extension Engineer at the University of Nebraska-Lincoln’s Institute of Agriculture and Natural Resources, explains how it works: “Residue protects the soil surface from water erosion and crusting by absorbing the energy of raindrop impact . . . Crop residue also protects the soil surface from the sun and wind, reducing wind erosion and soil moisture losses through evaporation. In addition, residue and growing plants keep the sunlight energy off the soil, which reduces the soil temperature in the heat of the growing season, further reducing evaporation.”

The no-till system (also called zero tillage or direct drilling, is a way of growing crops or pasture from year to year without disturbing the soil through tillage) not only reduces erosion and runoff from spring rains and snowmelt, it also increases infiltration of that water into the soil. Later in the season when it is hotter and drier, the roots of plants absorb the water stored in the healthy soil.

Diagram of the layers of good, healthy soil.
Diagram of the layers of good, healthy soil.
Illustration of a springtail insect.
Illustration of a springtail insect.

For more information, watch the following video "Careers in Agriculture" with Paul Jasa, UNL Extension Engineer.

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