I have lately been on quite a steep learning curve as regards swales/berms/hugel etc. Would be grateful if any of you could comment on my ideas.
I am currently considering putting swales/similar on a 0.25ha / 0.6 acre pasture paddock, which has 15% slope with shallow, free draining, loamy lime-rich soil over chalk. Zone 8, average rainfall approx. 900mm / 35in.
The reason for putting in swales/similar in would be to retain moisture and organic matter on what is a very free draining soil, prone to erosion by
water. The intention is to grow various food plants on the site. One question is whether the swales would do much, given that surface runoff on such soil is relatively low and that their most commonly stated function is to catch surface runoff.
Recommendations I have read for sandy soils are to have wider and lower swales. I would guess that having them on contour wouldn't be a problem given that a huge amount of water is not going to build up as it might with clay. Now I'd also guess that I'd want these to be spaced fairly closely so as to capture as much surface runoff as I can before it drains into the soil.
In digging the ditch, would I want to go down to the bedrock and try to compact it so that it holds more water? Remember, shallow soil.
Were I to put organic matter into the system, a la
hugel, the water absorbtion capacity would be increased. Which brings me to my next question. I see that in some cases people put organic matter into the ditch. Alternatively, it could be put at the bottom of the
berm. If I do the latter, which I am thinking might be better, would I want to stick the woody material as deep down in the soil as possible to maximise absorbtion? From a landscaping point of view this is starting to look like a case of stripping off all top/subsoil, and then piling up all of my berm material on contour. I intend to use a digger. Is this a crazy idea?
Finally, some sources advise compacting the
swale while others do not. Any advice there?
If you've read this far, thanks!
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