Chemical fertilizers are inorganic materials which are partly or wholly synthetic. Chemical fertilizers are added to the soil to increase the nutrient levels in order to support the optimal growth of plants. Chemical fertilizers contain the major plant nutrients nitrogen, phosphorus and potassium in different ratios according to specific soil needs. Also. the nutrients supplied by chemical fertilizers are immediately available to the plants as opposed to the organic fertilizers derived from natural sources which are more of a slow-release nature. Chemical fertilizers are often more cost effective and can be used in concentrated forms.
Sodium nitrate is also referred to as chilates or Chilean nitrate and contains refined nitrogen in amounts up to 16 percent. This makes the nitrogen immediately available to the plants and is one of the most valuable sources of plant nitrogen. Using sodium nitrate in the soil is particularly beneficial for young plants and garden vegetables. Acidic soils benefit the most with the addition of sodium nitrate. Sodium nitrate should not be used in excess as it can damage plants.
Ammonium sulphate is sold as a white crystalline salt with 20 to 21 percent ammoniacal nitrogen. The fertilizer is easy to store in large amounts in dry areas but is likely to form clumps during wet and humid weather. These lumps need to be ground before use. Ammonium sulphate is water soluble and the nitrogen in the fertilizer is retained in the soil particles. The chemical is likely to produce an acidic effect on soil and consistent long term use can lead to an increase in soil acidity. It is therefore advised to use ammonium sulphate with organic manures if long term use is planned. Ammonium sulphate can be used before or during sowing time or as top-dressing. Do not use too close to the seeds since concentrated amounts can affect germination.
Ammonia is a liquid gas form of chemical fertilizer consisting of 80 percent nitrogen. The fertilizer is available as a liquid since, under optimal pressure and temperature, ammonia becomes liquid. Aqueous ammonia is another form of ammonia fertilizer obtained from mixing ammonia with water. Both forms of ammonia fertilizer are used by adding to irrigation water or into the soil with specially devised containers. Ammonia is not recommended for use by the home gardener as its use and application is cost effective only when used on a larger scale.