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Farming: Is your soil compacted? Is water run-off a problem?

27 Feb 2020

Regenerative farmers reckon they improve their soil’s ability to absorb water in a big rain event.

They do this by seeding pastures with up to 20 different species of plant, some of what are purely designed to open up the soil to the air thereby increasing their soil’s ability to absorb water.

Some of the plant species in the pasture have roots that are creating pathways for air and water while other plants are designed to create organic matter stimulating the soil’s own pathway creators –worms.

Either way, a regenerative pasture increases the amount of rain that moves into the ground while reducing or eliminating the run-off of water with the subsequent loss of soil as sediment into waterways.

How does it work?

According to Gabe Brown, farmer and author of Dirt to Soil, One Family’s Journey into Regenerative Farming, water holding capacity depends upon three things:

  1. Having natural pathways through the soil from the action of roots and worms.
  2. Improved soil structure from an increased number of soil particles, known as aggregates. Soil holds onto water via a capillary film around each soil particle.
  3. Increasing the amount of organic matter in the soil.

When Gabe purchased his farm in North Dakota, USA, in 1991 his soil had poor water absorption. In a water absorption test it took one hour to absorb 13 mm (half an inch).

By 2009, after 14 years of regenerative farming, the water infiltration rate had improved to 250 mm (10 inches) in an hour.

In 2015 the infiltration rate had increased to absorbing 25 mm (1 inch) in 9 seconds. The second 25 mm was absorbed in 16 seconds.

Gabe tells us that for every 1% increase in soil organic matter he can store an extra 60,000 to 95,000 litres of water per acre. On Gabe’s farm, he went from 2% organic matter to over 6% in 21 years of regenerative farming.

By that stage Gabe’s land can store over 380,000 litres of water per acre which he says is absolutely critical to his operation.

In Gabe’s talks to disbelieving farmers across the States, it is not the amount of rainfall in an area that is relevant (disgusted looks all round), it is the ability to hold on to that water and store it underground that matters. What he calls effective rainfall.

It reminds me of Doug Avery’s system of storing water underground in the roots of his lucerne for the next crop he plants over the top.

How exactly does Gabe achieve this? He calls it his five principles of soil health:

  • No tillage. He direct sows his pasture and all crops.
  • Build diversity using a wide range of cover and cash crops. He encourages a diverse range of insects and birds too with his pollinator/predator strips of perennial grasses and flowers.
  • Quick rotation of grazing animals.
  • Never leave the soil uncovered by organic matter or plants.
  • Keep living roots in the soil for as long as possible over the annual cycle. Don’t leave the land empty. Plants feed the soil microbes, the soil microbes depend on plants, and if there are no plants the soil microbes starve.

Get your own copy of Gabe’s book, "Dirt to Soil". It is available on all the main book websites.

You won’t be disappointed.

Keep asking great questions …

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