Friday, January 20, 2012

Hydraulic Soils

I had to do some reading for today's blog. A good friend in Pennsylvania posted a really serious question entitled "hydraulic soils" on Crop Talk.

He is referring to the ability of soil to absorb water, or hydraulic conductivy of soil. Each soil has a natural hydraulic conductivity to move water through it. This conductivity has been greatly altered since man started tilling the soil for food production.

k is the coefficient for hydraulic conductivity, not potassium and usually written as ks. Darcy's Law states that J=Ki.

Where I live, I have two distinct soil formation types. The old Illinoian Glacial Till which is considered to be about 100,000 years old since the Illinoian Glacier created this soil and the Wisconsin Glacial Till which is considered to be about 10,000 years old since that glacial event formed it.

The natural conductivity of the two major soil formation types are quite different. The hydraulic conductivity of the older soil is much less, making it more poorly drained. The newer soil conducts water much more easily, making it moderately drained in most cases.

We have a situation where 60-70 inches of water fell on these soil this past year. Water is both a blessing and a curse. Six feet of water is a lot of weight! One inch of rain on one acre is 27,000 gallons and weighs 13 tons per inch. 72 inches times 13 tons is approaching a thousand tons of weight that fell on one acre this year.

Basically, most soils are not able to conduct all of this water and weight and are damaged by it. Farmers struggled to get the crop out this fall and we still have corn and beans unharvested in Ohio. The best we did on this farm was leave cleat marks the depth of the cleat of the tires. That is compaction.

Some fields are so rutted they look like you could lay tile in the ruts but they are pretty crooked as the farmer fought to keep the combine straight. How do we handle these situations?

No one has an answer but after 60 years of observing, I know for me the least amount of tillage I can do to get the next crop in the better. The soil will have to naturally heal and I have to understand those ruts will probably never fully heal in my lifetime.

Some farmers will try to rip below the depth of the rut but I don't see enough dry weather in our forecast before planting to allow that to happen. You may do more harm than good. Ideally we might take those fields out of production this year and start rebuilding them for notill. Economics is not going to allow that to happen so some tillage will be needed.

Other farmers will try to catch the soil in such condition they can blade or fill the ruts, lightly work and plant the next crop. Each farmer will have his own solution to the problem but none of them will be ideal. Some will just be better than others.

Increased tile installation and cover cropping will help as much as anything in my experience. Gypsum may improve conductivity on these soils, contact an expert before you use that as your only solution. No one thing is going to heal these damaged, disrupted soils.

It's a hard question today but one many farmers face at one time or another. Weather remains a hot topic on the farm every day because it controls our efforts and often our destiny.



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