I don't think petite is a height so much as a body shape. I have seen tall women shopping in the petite section because they have a short waist or shorter arms or wanted a skirt that fits them better than the regular ones, and I have seen smaller women shopping in the junior/misses/womens section for similar reasons.
Sweet clover needs a high pH, 6.0 or higher, for proper nodulation to occur, and it has a higher calcium requirement as well. Sweet clover is able to obtain phosphorus from relatively unavailable soil phosphates and will grow on soils where alfalfa, red clover or ladino will fail.
Check out this page for a simple soil content test. The soil's pH rating is also important. This rating tells you the relative acidity and alkalinity of the soil (this page explains the concept). The ideal pH level is around 6.5 or 7, but levels vary between different grass species and climate conditions. You can find out your soil's pH level with a home test or a professional test. If you need to substantially increase the acid level, add sulfur.