Alkaline clay soil seeking acidic amendments
I was getting horse manure for my roses but will cut down next year since: At various stages of decomposition (6 to 1 year), horse manure tested more alkaline than my clay soil (pH of 7.7 - stables use lime to deodorize their stalls). Also the sawdust and wood chips bedding in horse manure rob the soil of nitrogen as they break down. One University Extension recommends stables adding nitrogen fertilizer to get rid of their horse manure easier.
One web site recommends mixing a bag of pine park mulch with the soil. I was testing EarthGro topsoil pH - very alkaline at 8, but the same soil under a pile of pine barks tested less alkaline after 6 months.
Last year we piled up grass clippings on tomato bed in the fall as mulch, and did not rototille into the soil when spring came. It was the worst crop of tomato in over a decade: verticillium wilt, or root rot took over when we had a wet summer. Other years we rototilled grass clippings in the soil in May and had bumper-crops of tomatoes.
I plan to clip off evergreen branches from neighbor's old Christmas trees and use on my soil. In the past I used evergreen branches as mulch - it worked great in suppressing weeds. Which is better, mixing evergreens with soil, or using them as mulch on rose beds (prefer acidic 6.5 pH) or tomato bed (also prefer acidic soil)?
The Moo manure had been tested alkaline by others, and when I tested in red cabbage indicator, it was as green as baking soda. Do you know of any bagged cow manure or bagged compost/hummus which tested acidic, like pH of 4? Thank you for the info.