Try this!

A pile of ...
... horse manure. We have good experience with the use of a big pile of fresh horse manure to start our garden season earlier. Early spring time, about half-March, we fill a wooden collar (80x120x60cm) until the edge with fresh manure. Add some buckets of warm water to start the burning process. You can insulate the container extra, but at least cover the whole thing. The temperature can rise up until 60º C or more. If the temperature is not rising, add some more warm water. Or the manure was not fresh enough. After about a week the temperature will go down again. Then you can add a layer of soil in which you can seed the vegetables you want to grow. We always have spinach, lettuce, endive and radish. As soon as the plants germinate, make sure that they get light. Now it is important to pay attention to light, water, frost and ventilation, like in a green house. We used the same principle by just dumping a pile of poop. We start this in mid-April and use it for zucchini, pumpkin, tomato and corn. The result was fantastic.  Good luck!