With gardening, it has long been recognized that to improve the nutrient content or characteristics of the soil, it is necessary to fertilize the soil itself. Within organic gardening however, the use of synthetic is not used. Instead, most gardeners will use decomposing organic matter in the soil to do the same job of most synthetic fertilizers. This is much healthier for the soil as the organic fertilizer contains many more natural complexes that contain micronutrients such as zinc and iron for the plants to absorb.
There are three major nutrients that crops respond to: phosphorus, nitrogen and potassium. All organic materials contain these three nutrients but obviously in varying ratios so when trying to fertilize your crops it is important to combine the materials to get the levels of each nutrient you need. For example, manure is full of nitrogen, but is lacking in the other nutrients, so it is important to combine the manure with another material that is higher in the other nutrients. However, it is important to remember that fresh manure should never be used on food because it can be detrimental in terms of health and safety, while other nutrients can require special handling, as adding them on their own can be more detrimental to the soil in general.
The best way to fertilize is to compost the major nutrients with soil and then add it to your gardening where it is needed. Sawdust for example is low in nitrogen while high in other nutrients. In this case, it is best to layer the sawdust with soil and another material high in nitrogen so that you get an even combination too then add to the garden. This can help reduce the risk of ‘burning’ the plants with materials too high in nitrogen while also avoiding temporary nitrogen deficiency that can come with materials too low in nitrogen being added to soil. When you have a combination of all these nutrients, you can fertilize your soil safe in the knowledge that it will be receiving all the nutrients that you need.