Turning Soils into Sponges: Mitigating Drought and Reducing Flooding

posted in: Water | 0

 by Christina Allday-Bondy (copyright 2019 – 2020)

Soil science is making great strides in understanding the ecology of the soil and it’s influence on the water cycle and the atmosphere. There is increasing interest in a more resilient agriculture, one that more successfully withstands climate change.

Innovative farmers and ranchers have already found (or rediscovered) some management solutions that increase the capacity of soils to hold water resulting in blunting or delaying the effects of drought and decreasing runoff that floods fields; erodes soils and damages communities.

In New Mexico, the JX Ranch increased soil carbon 38% with planned grazing. The water infiltration rate increased 33% and static well measurements improved by 1 – 2 feet. Well flow rates at the ranch headquarters increased from ¼ gallon per minute to 1.5 gallons per minute. As a bonus to the water retained, nitrogen increased 11%.

In North Dakota, with an average annual precipitation of 16 inches, farmer and rancher Gabe Brown has improved soil conditions from a rain absorption rate of one-half inch per hour to eight inches per hour.

In central Texas, on the Kerr Wildlife Management Area, which is closely managed with cattle for the benefit of wildlife – particularly two Federally endangered birds — an overnight 6-inch rainfall dumped an estimated 90 million gallons of water in a small catchment. A 60-foot water gap (fence crossing of the drainage) was still standing the following morning and the minimal runoff water was clear.

On one acre a 1% increase in soil organic matter increases the water holding capacity of that acre by 20,000 to 27,000 gallons. Let that sink in (pun intended.)

What does this mean for New Mexico?

On State Trust Lands alone (9 million acres) a mere 1% increase in soil organic matter would capture 225 billion gallons of water – about one third of the capacity of Elephant Butte; more than three times the capacity of El Vado Reservoir; nearly 14 times the capacity of Cochiti Reservoir; and almost 10 times the annual water usage of Albuquerque.

According to the 2017 US Census of Agriculture, New Mexico has about 41 million acres in agriculture. Improving soil organic content by 1% on these would store about one and a half times the capacity of Elephant Butte. That’s a lot of water that isn’t lost to runoff, flash floods, and evaporation; and available to grow crops and pasture.

Another way to think about this is in terms of rainfall. At 27,000 gallons of water per acre per inch of rainfall, a one-inch rainfall event could almost completely soak in.

And we’re only talking about increasing soil organic content by 1%. There’s every reason to think it could grow from there, since beneficial practices tend to be self re-enforcing and compounding.

Organic matter in the soil is carbon based. It comes from plant residues and the billions (in healthy soil) of organisms comprising the soil food web. Water follows carbon. More evenly moist soil fosters increased populations of microorganisms that process and deliver many nutrients to plants. When these organisms thrive, plants thrive.

The Union of Concerned Scientists recently released a report, Turning Soils Into Sponges: How Farmers Can Fight Floods and Droughts that summarized their review of over 150 field experiments across six continents – looking at various methods to understand their “ability to improve soil health and increase resilience to droughts and floods.”

In both crop and animal agriculture, approaches that maintain living cover, particularly incorporating perennials, are most successful at absorbing and holding water. No-till, intercropping, more diverse crop rotations, use of cover crops between crop seasons, applications of organic material, improved livestock grazing and, diversified farming systems that incorporate perennials were all successful to varying degrees.

Increasing organic matter also adds carbon, nitrogen, phosphorus and other nutrients to soil. Farmers can use fewer inputs of fertilizer, fossil fuels to power tractors, irrigation, and time as a result. Decreasing costs may save many family farms.

But wait, there’s more good news to the story: carbon drawdown. Remember basic biology? Plants take in carbon dioxide (CO2) from the atmosphere; store energy in glucose; build leaves, stems, flowers, fruits and roots; and give off oxygen. Left alone they decompose on, and in (roots,) the soil.

Plants can literally pump carbon into the soil if we pay attention to what we’re doing. NMSU scientist David C. Johnson at the Sustainable Agriculture Institute suggests that taking advantage of plants’ ability to capture carbon is a vital component in combating climate change. Dr. Johnson is not alone.

Many well-recognized leaders in the climate and soils communities (Bill McKibben, Bill Hansen, Rattan Lal, and Christine Jones) have come to the same conclusion. The Rodale Institute, and others, believe that carbon sequestration in soils could completely offset fossil fuel emissions. The Paris Climate Agreement (COP-22) included the 4 per 1000 initiative that calls on nations to increase the carbon content in the top 40 cm of soils by 0.4% per year.

Every tiny bit of land — even your backyard — offers an opportunity to store water and reduce flooding; drawdown carbon and blunt climate change.

Several states, including New Mexico, have created programs that encourage and support resilient or regenerative agriculture. The New Mexico Healthy Soil Program offers incentive payments to farmers, acknowledging the public good that these practices offer. A number of resource materials are offered here: https://soil4climate.org/resources/

What if we could rehydrate New Mexico?  

(This article was revised from an earlier version originally published by Green Fire Times in 2017, www.greenfiretimes.com)

About the author: Christina Allday-Bondy has degrees in botany and natural resources policy. She had the good fortune to work on climate change for Commissioner Jim Hightower at the Texas Department of Agriculture; and own a land and wildlife management consulting company. She is currently a member of the New Mexico Healthy Soil Working Group and the New Mexico Food & Agriculture Policy Council. She also serves on the Estancia Basin Water Planning Committee and the board of the Soil Carbon Coalition.


County-by-county breakdown:

CountyAcreage in Agriculture* 
Increased Water Capacity Increased Water Capacity
in thousands of gallonsin acre feet
Bernalillo221,495 5,537,375 16,994
De Baca1,182,22429,555,60090,703
Dona Ana528,27013,206,75040,530
Los Alamos
Rio Arriba1,362,06234,051,550104,500
San Juan2,551,47063,786,750195,754
San Miguel2,269,55456,738,850174,125
Santa Fe717,70417,942,60055,064
* 2017 US Census of Agriculture

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