Hi everyone,
I have a liming question. Last year was my first year
gardening since I was a kid. The soil started out with a pH of 5.5, I added the recommended amount of lime to get it to 6.5, but when I tested it recently prior to planting for this year, it came back at 8.0. So what did I do wrong? And how do I fix it?
The soil is a silt loam with about 1/3 sand, 2/3 silt, and only a negligible amount of clay. When I started last year, I measured the pH myself several times at 5.5, using a Nasco kit; this number was later confirmed by a professional
soil test from the
local state university.
I used Pro-Select Prill Limestone and followed the recommendations on the side of the bag. When the starting pH is 5.3-5.6, and the target pH is 6.3-6.5, these call for 65 lbs of CaCO3 per 1000 sq ft for sandy loam. (I have silt loam, but I followed the recommendations for sandy loam, which call for the lowest amounts of lime except for very sandy soils.) This works out to about 11 lbs of CaCO3 for my 175 sq ft of beds, or 13 lbs of prill limestone (which is 87% CaCO3). I actually added only 7.5 lbs, or a bit more than half the recommended amount.
The only other things that I added were ~1/2" of
compost with a tested pH of 7.0, alfalfa meal, phosphate, and crushed granite. Additionally, I was just looking at a test of our well
water from a couple of years ago, and its pH is 8.0 (has high levels of calcium, too).
So where did I go wrong? Is it possible that one season's worth of
watering with pH 8.0 water could have affected the soil pH so much?
Should I have made some allowance for the pH-altering effect of the other soil amendments? If so, how does one go about calculating that allowance? Any other ideas?
Many thanks,
permanoob