Plant fertilizers are made from either organic or inorganic materials. Chemical fertilizers have a combination of nitrogen-phosphorus-potassium in a percentage ratio called the N-P-K number. Organic composted fertilizer is made from plant and animal materials that have decayed become nutrient-rich. Plants have a variety of nutritional needs specific to their development. Fertilizer is applied according to those needs.
Chemical fertilizers deliver additives such as nitrogen, phosphorus and potassium to plants to boost growth quickly. Nitrogen encourages growth of stems and green leaves; phosphorus boosts flower and fruit production; and potassium strengthens stems and leaves. Inorganic fertilizers are designed with percentages of combination of these three elements. Combinations can be specific to rose bloom production, citrus production and vegetable growth. Adding bone meal or ammonium sulfate as a fertilizer creates higher soil acidity. Plants such as azaleas and lemon trees benefit from slightly acidic soil.
Compost is the common name for organic fertilizer. Types of compost differ for specific plants and flowers. Organic fertilizer is made when animal and plant debris decay and become a nutrient-rich soil. It is a natural process of decay that gardeners can speed up by applying water, air and heat. Organic compost is also called humus. Compost as a fertilizer adds living organisms to the soil which become nutrients for growing plants. One advantage of using compost as a fertilizer is that it won't burn plants or poison pets. It also does not require a specific timetable of application and watering because of the slow-release of nutrients. Organic fertilizer is often preferred for growing vegetables of all kinds because of its safety.
Concentrated liquid fertilizers such as fish emulsion, orchid food and African violet plant food are convenient for use inside the house. They can be mixed easily in a small watering can. Compost tea is a similar fertilizer variety made by mixing a small amount of home-made compost in water. It is used on young plants in the garden or houseplants. Some inorganic fertilizers are sold as "slow release." They are depicted as "3:1:5 SR." Organic compost is always slow-release because its compounds are natural microorganisms that decay over time.