These inorganic fertilizers, some of which are readily soluble in water, are the least expensive and can be bought at any garden-supply store, but they require some care for safe application during the growing season. Many of these organic or synthetic forms are incorporated in other all-purpose fertilizers, which are widely available. Processed fertilizers having nutrients derived from various manure sources are becoming more widely available. These fertilizers will have the guaranteed minimum percentages of the major nutrients listed on the labels. The natural and synthetic organic fertilizers may be more expensive, but the danger of burning plants is reduced provided the recommendations on the package are followed explicitly.
Barnyard manure is relatively low in nutrients and usually contains many weed seeds.
Weed-free fertilizers are preferable even when manure is available without cost. Commercially dried manure products are very expensive for the benefits received. Most of their components are derived from inorganic sources. Usually the recommendations are to dissolve a specified number of ounces or teaspoonfuls in a particular volume of water. When recommended rates are used, they can be applied safely to growing plants.