Do wood and straw raise soil potassium levels?
Week before last was the uncritical
summary of Steve Solomon's The
but this week I want to look at his claims in more depth. For
example, Solomon wrote that potassium is
found in large amounts in woody stems of trees and in lignified stalks
of grasses, so if you practice hugelkultur or mulch with straw, your
potassium levels are going to be too high. Sure enough, my
potassium levels are higher than recommended, but is it due to the wood
As you can see in the
table above, the absolute amount of potassium in the soil is higher in the beds, but
potassium's percent saturation is lower. If your head is
whirling, remember that the cation
(CEC) determines how many positively charged ions can stay put in the
soil, and CEC is increased by adding organic matter. The higher
CEC in the forest garden beds gives room for many more cations, so even
though using lots of woody amendments increased the absolute amount of
potassium in the bed, the cations are actually more in balance in the
beds than they are in the untreated aisles.
My paperback walks you through the basics of soil testing and starting a vegetable garden.
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