Adding organic matter like cow manure is always a good idea. This is also a good time to check the pH of the soil and add lime if needed. Applied now, it will have all winter to correct the pH of the soil…it takes about 6-8 weeks so the soil will be nice a sweet and ready to go in spring. HERE’S A LINK that describes how to do a pH test…easy peasy, Vegetable gardens like a pH of 6.5 to 7.0. Blending in some Bio-Tone organic plant food when the soil warms in spring would be the best way to supercharge the nutrient level in spring prior to planting, More on Bio-Tone HERE.