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Southeastern Idaho

Does anyone know how deep and how wide the roots go on these giants? I'm going to prepare my first patch in a week or so and I know about 1' down is VERY solid, unfertile sandy loam. I'm going to be mixing potting soil, last year's tree leaves and A LOT of 6 to 8 year old cow manure into the soil... How deep do i need to go?

3/11/2014 9:42:52 PM

aurora, IL

You dig 2 to 3 feet down at the planting site and also get a soil test done.

3/11/2014 11:00:44 PM

Colorado

Most of your rooting is in the top 12 inches. You want to go deeper than that if you need to improve drainage-ie if youve got clay or hardpan. The rooting from your planting site can go 25 feet plus radius-50 feet diameter.

3/12/2014 1:17:21 AM

Hinckley MN

It is very rare for a soil to have oxygen at 25 ft depth. Roots need oxygen. Over half of the roots will be in the top 6 inches of soil, 75% in the top foot and 90% in the top 18 inches for most annual plants. You may get some roots to go deeper, but primarily only at the planting site. There is an increasing cost of effort and diminishing return for that effort to digging deeper.

3/12/2014 11:25:21 AM

Springfield, Missouri

Cojoe is saying that roots will be in the top 12 inches, but that they may travel up to 25 feet. I have pulled tap roots out and had them go over 12 feet before they broke.

The only reason to go 2 or 3 feet down is to break a hardpan. If you have a hardpan use a subsoiler or broad fork. Be careful not to mix the top soil with the subsoil.

3/12/2014 1:24:00 PM

http://www.bigpumpkins.com/msgboard/ViewThread.asp?b=3&p=502995
there is a link in this discussion that will take you to a study of root systems.might be of some help to you.

3/12/2014 1:49:29 PM

aurora, IL

Logan Duncan, mixing the top soil with subsoil wouldn't that be called double digging. Also, would it be a good ideal to mix in composted manure or other soil additives.

3/12/2014 2:33:47 PM

Germany

In my opinion one should treat every soil in an individual manner, because some people have a 1 ft dark top soil layer whereas others have a 2 inch layer of top soil and a rock solid subsoil. Hence, I think it might be better to discuss general aims to be achieved rather than generalizing a particular procedure for all sorts of patches.

Mixing top soil and sub soil, yes or no? In case of an already 1 ft thick layer of top soil I would say NO, but in case of the 2 inch layer of top soil I would definitely say YES. In both cases one would most likely aim at the following features of the resultant soil:
Most of the organic matter in the upper 1/2 ft of the top soil but still a good amount of organic matter down to somewhere like 3/4 or 1 ft. Deeper than 1 ft excessive organic matter becomes more and more likely to cause troubles because of rot (less oxygen available in such depth). Some little amounts of organic matter in this depth, howere, could perhaps be beneficial by means of maintaining good drainage of the soil (which otherwise would form a clay pan again much earlier).

3/13/2014 3:57:15 PM

Germany

In my particular case, I do have some kind of sandy soil with small amounts of loam/clay, and the top soil layer is about 1 ft thick. For the plant sites I have removed the 1 ft top soil layer, then I had treated the hard sub soil with a clay pick and mixed it with some perlite. Then I exposed this sub soil (covered with plastic sheets) to the sun for 3 days, and then I piled up the top soil again. While digging out the top soil I noticed that it is already in a great condition (no compaction, good structure stabilized by the roots of the winter rye cover). Thus, in the surrounding parts I won´t treat the soil into the depth of 1 ft. Instead, I will mow the winter rye, then I will till the top 6 inches layer (in order to have the organic matter in the top layer, for better decomposition, better access to oxygen), and the AG roots which grow into this 6 inches layer of tilled top soil can definitely grow deeper down as they want to, but I retained the structure of this lower soil layer (its channel and capillary structure), and the roots can attach to this layer like to a fluffy sponge which allows for drainage, but also helps to supply water by the action of its capillary system, whereas the fluffy top-top-soil then has less of a capillary system and thus limits evaporation of precious sub soil moisture.

3/13/2014 3:57:19 PM

Germany

Christopher, the double digging is a small scale substitute for plowing (you can reach down into the same depth), and I think it is a great way to create a 1 ft layer of good top soil, but I wouldn´t recommend to do that every year, because every double digging will destroy the soil structure.

3/13/2014 4:02:00 PM

Springfield, Missouri

http://www.bbc.co.uk/gardening/basics/techniques/soil_digging1.shtml

Double digging should be used as a means to improve soil drainage if a hardpan has formed. The minerals in the subsoil are in a "reduced" form. While the minerals are in a reduced form they are generally unavailable to our plants. If the subsoil is incorporated with the topsoil then these reduced minerals can pull free oxygen from the root zone. A lack of oxygen can suffocate roots and beneficial microorganism. Subsoils often contain higher levels of aluminum and other heavy metals that can be deterimental to soil health.

Here in Southern Missouri we have very little top soil. I have found that it is easier to make raised beds than deal with heavy red clay.

3/13/2014 8:28:44 PM