If you got any bat caves around your house go there. Scoop up the bat shit and feed it to your plants. They love that shit. Professionals like to call it bat guano :21: Or you could do like naturalhi said and feed them your left over tator tots
Why is everyone so afraid of nutrients!? All I ever see are posts like this, "Can I feed my plant urine" and the like. It's not as if fertilizer was expensive, hard to find, or illegal to purchase. Every town has a garden store or garden center within a larger store and any of these would contain products that are adequate for the task at hand, so whats the problem!?
Anyway, I would recommend starting a compost pile. This will give you a source of nutrient rich dirt and worm castings (from red worms, if you add them).