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Vertisol with expansive clay C sublayer

The lower parts of our farm (Central Tanzania, East Africa, ~70 acres, in development since 2017) are vertisols (~1m) with an expansive clay sublayer (don’t know how thick, but at least 2m). During the rainy season it can get flooded for a few hours (because of landscape degradation surrounding our farm) until surface waters run of.

Right now I’m trying to plant grasses (vetiver, rhodes grass, cenchrus) and fodder trees (leucaena, gliricidia, and faidherbia) to develop a grazing area.

Any trees that could grow and maybe even penetrate the clay layer? Any other thoughts for improving the area?

Maybe I’m displaying my ignorance here but I was thinking that Vertisol is basically clay soil but you say that beneath the vertisol is a layer of clay. So, not sure I understand.

In terms of root penetrating power, I am delayed in the test I spoke of last month on this topic and so have not fully tested yet but initial indications are Papaya, Mango and Guama are among the best. For short term crops, Millet and Sorghum are good. Not sure about the penetrating power of Sunn Hemp but as it germinates, it has very prominent taproot. Best to you!

Yes, of course it is. But the top layer is heavily self-mulching, which leads to better water penetration because of the high humus content. Beneath it there is a layer of pure white clay that is pretty much water-proof. Right now there only grow annual plants (grasses and stuff), and a few indigenous bushes.

I would like to increase the water holding capacity of this area by penetrating deeper into that sub-soul layer, so planting deep-rooted grasses and trees would be the way to go, I guess. But as the area becomes soggy during the rainy season (pretty much all the run-off from the surrounding areas flow over there), not all trees will do equally well. That’s why my question on what to plant best in order to improve that part of our farm.

If there is a time of the year when the soil is not super saturated I think all of the plants that I listed will grow long enough for the root to make good penetration before the plant dies as a result of being waterlogged when the heavier rains come. That is basically our strategy. Plant plants with penetrating roots and then kill them so the deep roots provides channels for water to move. We also do that with vetiver both to provide water channels but also to provide organic matter deep in the soil for the microbes. In addition, the organic matter attracts soil insects which further help create water channels.

In my previous reply I failed to note the obvious. The best candidates for growing would be what is already growing nearby. So look in fence rows and hedge rows and unused land to see which trees tend to thrive. Interplant some of them with your crops so the roots can penetrate and then kill the tree so the decaying roots form those channels into the subsoil.

Hehe. You’re right, to best is often the most overlooked. I will have a look.