People often say “the biology eats first”. If you put down a product that has a high C/N ratio, like wood chips, the biology will pull out whatever nitrogen they can to match with the carbon, and since they eat first it will sequester any nitrogen that is available before the plant can pick it up. You can sometimes add a higher N product to the mix (like manure) to get a quantity of n that will be able to both feed the crop and the biology.