"Organic matter is THE best amendment for any soil type. It increases soil moisture retention, improves soil structure and decreases soil compaction." -Katie Wagner, USU Extension
Over the winter months these materials will start to break down, and come early spring, decomposition will be well under way putting you lengths ahead of others who don't start adding these materials until right before they plant!
Remember decomposition often means a depletion of nitrogen in the soil, so it's best to get this process going BEFORE you start planting those nitrogen loving garden plants. "The addition of too much organic matter in one application can throw off the ratio between carbon and nitrogen (C:N ratio) in the soil. If the C:N ratio in the soil exceeds 25:1; soil microorganisms will scour the soil in search of nitrogen. Soil microorganisms need both carbon and nitrogen to survive. Therefore, if the soil carbon content greatly exceeds the soil nitrogen content, microbes will consume soil nitrogen causing plants to become deficient in nitrogen." -- A Guide to Common Organic Gardening Questions
So get a jump start on your spring garden before the snow falls. Because.......if you build it THEY will come!
For even more tips on improving your Garden Soil click HERE