These recommendations are then used to make decisions about present and future fertilizer applications. Soil testing is the most important single guide to the profitable application of fertilizer and lime. When soil test results are combined with information about the nutrients that are available to the various crops from the soil profile, the farmer has a reliable basis for planning the fertility program on each field. Traditionally, soil testing has been used to decide how much lime and fertilizer to apply. If livestock are present in a sustainable system the manure will be used as a resource, not as a waste.
Manure is an excellent source of plant nutrients.
The use of manures does not preclude damage to water quality. As previously discussed, a conventional systems tends to be monocultural with one or two crops. In a sustainable system there is diversification in the number of crops grown. First in a system where many different crops are grown the labor requirements are spread out. Secondly, diversity aids in pest control.