It's easy to overdo it with manure in the garden. Manure is high in nitrogen, which is great for plants, but too much can burn them. The general rule of thumb is to use no more than 1/2 pound per square foot of garden space. So, if you have a 10x10 foot garden, you would use no more than 5 pounds of manure. Steer manure is especially high in nitrogen, so you may want to use even less than that.