Soil Water Retention Is Key to Farming Productivity

February 22, 2019

Soil Water Retention Is Key to Farming Productivity

Water is vital to carrying on a plant’s most basic and essential functions. Water helps carry nutrients throughout the plant, keeps cell walls strong, and is a crucial component in carrying out photosynthesis. Without water, plants cannot survive, so optimizing soil that is able to effectively store and retain water will help you keep your crops happy and healthy.

Employing soil that is able to hold a high amount of moisture can help you reduce the negative effects of droughts, floods, erosion, and degradation while also improving the quantity and quality of your crop yield. If you can effectively manage and optimize the water retention in the soil on your farm, you can create a more sustainable and productive agricultural space that is minimally susceptible to periods of extreme weather.

What Is Soil Water Retention?

Soil water retention is the soil’s ability to hold water inside its pores and hold onto moisture rather than allowing it simply to obey gravity and pour through the earth’s surface. Soil’s ability to effectively retain water is largely attributed to its porosity, texture, and structure, according to the Noble Research Institute (NRI). Porosity measures the open spaces between soil particles, texture refers to particle size, and structure has to do with how the soil particles arrange to create stable units called aggregates.

Soil Water Retention by Soil Texture

Fine soil, like clay, is characterized by smaller particles and more numerous pores, while coarser soils, like sand, have much bigger particles and less space in between each one. Water likes to stick to fine particles with lots of smaller pores, while coarse soils offer less water retention as moisture can percolate and drain past large particles and through open pores with ease.

Each type of soil has a finite amount of water it is able to hold, which is called its water-holding capacity, which is largely determined by the soil’s texture. Soils with higher percentages of fine particles like those of clay and silt and thus more surface area will have a higher water retention capacity than those largely made up of sand particles.

Photo courtesy of Noble Research Institute

How To Improve Soil Water Retention

As a farmer, it may seem as though, at times, that working to alter soil’s porosity, texture, and structure to optimize its soil retention abilities is a daunting and even insurmountable task. When dealing with complex, living ecosystems found in soils, it is only appropriate to feel like our efforts to enhance soils are too insignificant to make a meaningful impact and result in a return on investment. Although, if we aim to take simple steps each season and work to support soil’s naturally occurring cycles over time, our seemingly insignificant steps will ultimately lead to giant strides down the road. So let’s start with a few small steps to enhance our soils to improve water retention efficiencies.

A common way to raise water retention capacity on your farm is to increase levels of soil organic matter (SOM), which is decayed material that originated from a living organism. Organic matter can hold 10 times its own weight, and increasing SOM by just 1% helps soil hold 20,000 gallons more water per acre, according to the Natural Resources Conservation Service (NRCS). The Cool Terra® soil amendment exists as a tool to increase soil organic matter. It is a carbon-based material that is highly structured and resists breaking down biologically over time like other carbon-based soil amendments. Other practices such as cover cropping can also aid in promoting soil organic matter levels through residues the crops deposit back into the soil.

You can also take preventative measure to protect your soil against natural erosion and degradation that breaks down the integrity of your soil’s structure and lowers its water retention abilities. Tilling, for instance, breaks up particles within the soil, creating large pores that water can easily pass through without sticking to the soil itself. Reducing tillage or employing no-till methods will help sustain effective soil structures.

It’s great to see an increase in the acres of American farmland using cover crops and reduced disturbance practices. This is a step in the right direction and will aid in the development of a robust food system that can feed our increasing population. However, if we want to make additional environmental and productivity gains, it is time to consider a third strategy when trying to improve SOM levels – adding Soil Organic Carbon (SOC).

Evidence for Soil Water Retention Improvements

Cool Terra's Impact on Soil Water RetentionSoil Organic Carbon (SOC) consists in three forms – Labile, Humic, Recalcitrant – each complimenting the other to improve soil health. Labile is rich in nutrients and highly degradable, which is mostly delivered in compost or manure. Humic, such as humus and fluvic acids, are complex organic compounds that are highly degradable, and play a major role in the organic fraction of soil.  This brings us to Recalcitrant, also known as fixed carbon. Cool Terra® is a durable, granular, fixed carbon material that can be added to soils as an amendment to optimize soil water retention capacity, create a beneficial environment for microbial growth, improve the root structure of the soil, and enhance the carbon level balances of a grower’s soil by sequestering carbon. In many environments, the Cool Terra biochar-based soil amendment products can optimize water-holding capacity in the soil, lessen evaporative water loss and, most importantly, increase plant “available” water – the water that plant roots can actually access – when compared to controls. For growers who desire to be more efficient with water, Cool Terra® can be a highly effective tool to help your soil do more with less.

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