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.
Test the soil for proper pH levels. If you are reseeding a previous pasture that was not successful, the problem may have been the acidity in the soil. You want the soil pH to be around 6.5 for pasture grass. You can achieve this by adjusting the amount of fertilizer.