Lawn fertilizers are traditionally high in nitrogen since they are applied to make grass green and thick. Using lawn fertilizers on the vegetable garden is a mistake because leaves are not all that we are looking for. The nitrogen is important, but should be used to a limited extent. Phosphorous is useful for flower production and root growth. It is especially valuable for tomatoes, peppers and plants from the cucumber family.
Potassium plays a major role in plant hardiness and vigour.
It makes cell walls thick and able to resist stress and disease. The effect of potassium can be easily seen if wood ashes, which are high in potassium, are applied to the soil. Very healthy growth is the result. If your compost supply is limited, another way to introduce organic matter to the soil is by planting a crop of green manure in the fall. After harvest, plant annual rye grass.