Gardeners who want to feed their plants can choose solid, liquid and even gaseous fertilizers. Although anhydrous ammonia is an option, most gardeners use either liquid or dry varieties. There are a few distinct advantages and drawbacks to using both types, but the main difference is how quickly plants have access to the nutrients available in the fertilizer.
Dry fertilizers are typically cheaper because they are lighter and have lower shipping costs. They offer plants a sustained feeding released into soil more slowly than liquid fertilizers. This means dry fertilizers do not require as many applications because the nutrients remain in the soil longer.
Liquid Organic Fertilizer
Liquid organic fertilizers are based on fish emulsions, compost and seaweed. They are harder to find than inorganic varieties, but are easily absorbed by plants and may be slightly safer than other brands. They are sold with less-concentrated nutrients. This can be an environmental blessing because of the decreased opportunity for unabsorbed chemicals to pollute the soil.
Liquid Chemical Fertilizer
Liquid chemical fertilizer is commonly used in large-scale farming because the cost of equipment needed to use it is not practical for individual gardeners. A few brands are simply dried fertilizer dissolved in water, while others contain the gas anhydrous ammonia. Liquid fertilizers provide nutrients that are more readily available for absorption by plants but can also be easily washed away by leaching, rainfall or irrigation. Highly concentrated fertilizers require additional water before application.
Dry Organic Fertilizer
Organic fertilizers are made entirely with naturally occurring sources such as bonemeal, fish meal and manures. These materials are rich in nitrogen, phosphorous and potassium, the three macronutrients needed by plants for proper development. Manufacturers often add other materials to aid in plant growth and to help retain nutrients in the soil.
Dry Chemical Fertilizer
Chemical fertilizers vary greatly in the balance of nutrients available. This aids in the feeding of plants that require specific levels of nutrients compared with a balanced mixed. Fertilizers may be manufactured as nitrogenous types, containing ammonium nitrate or ammonium chloride; phosphate types, containing rock phosphates or chemicals rich in phosphoric acid; and potassium types full of muriate or sulfate of potash, which has high levels of mineral deposits and salts.