Fertilizers

Management of soil fertility has been the preoccupation of farmers for thousands of years. Egyptians, Romans, Babylonians, and early Germans all are recorded as using minerals and or manure to enhance the productivity of their farms.^[1] The modern science of plant nutrition started in the 19th century and the work of German chemist Justus von Liebig, among others. John Bennet Lawes, an English entrepreneur, began to experiment on the effects of various manures on plants growing in pots in 1837, and a year or two later the experiments were extended to crops in the field. One immediate consequence was that in 1842 he patented a manure formed by treating phosphates with sulfuric acid, and thus was the first to create the artificial manure industry

Uses of Chemical Fertilizers

Chemical fertilizers are synthetic substances that provide the necessary nutrients for healthy plant growth and development. Chemical fertilizers combine synthetic forms of the primary macronutrients for plants such as nitrogen, phosphorus and potassium, as well as a variety of micronutrients and additives. Synthetically developed fertilizers provide the benefit of having more nutrients per pound than organic fertilizers, thus reducing costs. Chemical fertilizers have many uses for the average gardener and homeowner, as well as for commercial use.

Gardening

Plant and vegetable gardeners use chemical-based fertilizers for healthy plant growth. The nitrogen in fertilizer promotes cell division and leafy vegetation, phosphorus helps plants with photosynthesis and respiration and potassium helps plants absorb the other nutrients, according to NASA. Chemical fertilizers contain a higher concentration of macro- and micronutrients than organic fertilizers, which allows gardeners to spread less of a concentration for the same results. Depending on brand, chemical-based fertilizers provide varying levels of additives, which help grow plants faster and stronger. However, according to Pennsylvania State University, over-fertilization, a common problem with chemical-based fertilizers, can cause poor growth and even plant death. University or private labs can test soil samples to determine the recommended amount of fertilizer to apply for specific garden plants.

Uses & Benefits

With the global population steadily growing, it is important that enough crops are produced each year to provide food, clothing and other agricultural products to people around the world. Crops such as corn, wheat and cotton receive nutrients from the soil they are grown in; various crops deplete soil nutrients in different ways and rates. Some crop growth can deplete soil nutrients after just a few seasons of planting. Fertilizers play an important role in providing crops with the nutrients they need to grow and be harvested for nutritious food.

Fertilizers help deliver enough food to feed the world’s population. But they can do even more. A class of fertilizers called micronutrient fertilizers is engineered to enrich crops with vital nutrients that help support human health. For example, micronutrients such as zinc are important to human nutrition, especially children. According to a United Nations study, much of the world’s grain crops are grown in soil without adequate zinc; offering micronutrient fertilizers to grain crops enriches the grain with an important nutrient.

WHY DO FARMERS USE FERTILIZERS?M

Question: I’ve heard that fertilizers can have negative effects. Why do farmers use fertilizers?

Answer: All the nutrients in our food originally come from the soil. In order to create healthy crops full of nutrients, farmers need to work with healthy soil.

A large sprayer applies nitrogen fertilizer to a field. The equipment is assisted by technology that optimizes the application of fertilizer—using it only where needed on the field. This reduces cost to the grower. Photo credit: Bill Raun

Soils naturally contain many nutrients like nitrogen, phosphorous, calcium, and potassium. These nutrients allow plants to grow. When soil nutrients are missing or in short supply, plants suffer from nutrient deficiency and stop growing. When the nutrient level is too low, the plant cannot function properly and produce the food necessary to feed the worlds’ population.

Once crops are harvested for human consumption, the natural supply of nutrients in the soil must be “re-filled”. This is why farmers add nutrients to their soils. Nutrients can be added from a variety of sources—organic matter, chemical fertilizers, and even by some plants. This maintains the soil fertility, so the farmer can continue to grow nutritious crops and healthy crops.

Farmers turn to fertilizers because these substances contain plant nutrients such as nitrogen, phosphorus, and potassium. Fertilizers are simply plant nutrients applied to agricultural fields to supplement required elements found naturally in the soil. Fertilizers have been used since the start of agriculture. Native American people used crude fertilizers, such as burying a fish in their corn plots, and organic farmers use fertilizer from natural source, such as compost. Most farmers today use fertilizers that are either mined or manufactured.

Regardless of the source of the fertilizer, all plants use the same inorganic forms of fertilizer in the soil. Sometimes the source of nitrogen can be plants called “nitrogen fixers.” Many farmers use crops, such as soybeans and alfalfa (called legumes), that can remove naturally occurring nitrogen in the atmosphere, and place (“fix”) it in the soil for future crops to use.

Urea

Urea is the most widely used solid nitrogen fertilizer and is usually applied as granules, although it is sometimes mixed with ammonium nitrate and dissolved in water to form urea ammonium nitrate solution. When applied to soil, urea reacts with water to form ammonia, which makes the nitrogen within the fertilizer available to plants. Urea fertilizers deliver one of the highest amounts of nitrogen at 46 percent, with no phosphorus or potassium.

Ammonium Nitrate

A solid fertilizer typically applied in granular form, ammonium nitrate provides substantial amounts of nitrogen to the soil. The Fertilizer Institute indicates that ammonium nitrate is particularly effective at fertilizing specialty crops such as citrus and pasture lands. Ammonium nitrate typically provides 33 percent nitrogen.

Ammonium Sulfate

A by-product derived from the waste generated by coke ovens, ammonium sulfate forms when sulfuric acid is used to remove ammonia from the coal used to make coke. Ammonium sulfate is a solid material that contains 21 percent nitrogen.

Calcium Nitrate

This fertilizer contains 16 percent nitrogen in a nitrate form. Less effective than other nitrogen fertilizers due to leaching when applied to soil, calcium nitrate is often used in fruit and vegetable crops to provide a readily available source of nitrogen and also provides soluble calcium for soils that are calcium deficient.

Diammonium Phosphate

Where soils do not have enough phosphorus, diammonium phosphate can provide significant amounts of this chemical, at around 46 percent. The ammonia component of diammonium phosphate also delivers around 18 percent nitrogen. Highly water soluble, diammonium phosphate is often applied in liquid form.

Monoammonium phosphate

Another phosphorus fertilizer, monoammonium phosphate delivers even more phosphorus than diammonium phosphate, at 48 percent. The amount of nitrogen in fertilizer provides is somewhat less at 11 percent. The lower level of the ammonia component of this chemical lessens the risk of damage when applied to new seedling growth.

Triple Super Phosphate

Available in granular form, triple super phosphate is applied directly to the soil. While largely replaced by diammonium phosphate and monoammonium phosphate due to better storage and the availability of nitrogen within the chemicals, triple super phosphate is still in use both commercially and in home applications. Triple super phosphate is often combined with nitrogen-based fertilizers to provide a better, broad-spectrum application.

Potassium Nitrate

Potassium nitrate, also called nitrate of potash, is frequently used on vegetable crops including celery, potatoes, leafy green vegetables, tomatoes and several fruit crops, according to the Michigan State University Extension. The nitrate component of this chemical fertilizer works well with these crops. Potassium nitrate provides 44 percent potassium.