Somewhere in the PDM (I think) there was a reference that went something like:
if you angle the planting surface 1 degree toward the equator, it is the equivalent of being xx miles closer to the equator.
Naturally, I cannot find the reference again, and it might not even be in that tome, I've read so much this winter. Google-giver-of-all failed me.
Where is this useful fact buried? (really bad pun on angle of repose could be made, but I'm not good at such things)
Post by:Craig Dobbson
, master steward
Here is a reference from the book " The New Organic Grower" by Eliot Coleman.
Land in the northern hemisphere at a latitude of 43 degrees with a slope angle of 5% to the south with have the same solar climate as the area 300 miles to the south of it.
I'm not sure how to do the calculation for differing slopes and lattitudes but maybe this is a good place to start.
Post by:John Elliott
Each degree of latitude is 60 miles. Those would be of the nautical variety, statute miles are a little less than a nautical mile, but not much.
Post by:Jen Shrock
I remember coming across that sometime too. I think geoff lawton mentioned something about it. Something like for every 1 degree of increase in slope is like gaining 1 degree of latitude, for a surface facing the equator (obviously facing south for those of us in the northern hemisphere). I could be wrong, but that seems to stick with me.
Post by:Adrian Patch
(my first post after being a lurker for a longish while)
this is something I have wondered about now and then (while quite happy that I have a good south facing slope on my land). I have wondered especially how valid this sort of comparison is, and the assumptions that are being made. For instance, after reading Elliot Coleman's Winter Harvest Handbook I have developed a deeper appreciation of the role of shelter from wind in affecting the hardiness and productivity of plants; A slope might give a boost in some aspects of solarenergy received, but what about the importance of air temperature (which will depend on a lot of factors at the local site, but will surely not be equivalent to x hundred miles south by virtue of being above a south facing slope!) and how it is affected by wind (e.g., wind-chill).
If anyone knows of a good article/other source that explores this I would be keen to follow it up.
I am in the process of designing some shelter for veg beds on a south-facing slope that will allow me to offer protection from the wind while benefiting from the solar gain offered by the slope - and it can be quite a windy site! I guess it comes down to micro-climate!
Post by:Kelly Smith
i thought i heard Geoff mention that higher altitude makes the site conditions more/less hot, but that continental effect (distance from a major sea or ocean) had an effect also.
for me, im a long way from the ocean; thus i have a large continental effect, so i will generally have higher highs and lower lows than someone that is closer to the ocean.
i am also ~5300 ft up. Geoff mentions that every 100m (~325 ft) can effect the site similar to moving south 1* (warmer) in summer and 1* north (colder) in winter
basically saying that altitude amplifies the continental effect is how i took it.
this was from the online PDC videos. probably around disk 7-8 if i remember correctly.
i thought the slope had to do with what type of planting it received (slope stabilizing, food forest, fuel wood etc).
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