What is fertilizer?

Answer 1

Feriliser (or Fertilizer US spelling) is either a chemical or organic compound that is applied to plant for the purpose of providing supplemental nutrition to enhance all or a number of the plants growth characteristics.

As mentioned fertilisers are divided into two broad categories a) chemical and b) organic:

Organics are the oldest known form of fertilisers and have been used for hundreds if not thousands of years to increase the yield or condition of agricultural and ornamental plants. Organic fertilisers, as the name suggests are derived from "organic" or naturally found materials and include such things as composted vegetable materials and decomposed animal waste. They are normally applied liberally as topdressing to agricultural fields or production areas. The material needs to be decomposed as to allow the release of the nutrients into the soil. Organics are normally "broad spectrum" fertilisers that provide a whole spectrum of nutrients to the plant with one application.

Chemical fertilisers (again as the name suggests) are products derived from chemical synthesis (most are actually by-products of industry). Examples of these are Superphosphate and NPK (various formulations). Some formulations of chemical fertilisers are "dry" and granular or powder in nature. They are relatively easy to apply by machine (as for agricultural usage) or soluble in water for liquid or spray applications. They are all more concentrated in form than organics, thereby providing ease of application as well as value for money in one "package". The most efficient way to get nutrients to the plant for uptake.

The downside of chemical fertilisers is as they are soluble they are easily leached from the soil and can contaminate groundwater, normally resulting in algal problems. Again, because of the soluble nature they are taken up quickly by plants and the results of application are much faster to see than with organic fertilisers - again a negative factor is that if they are not used quickly they move through the soil and are quickly lost. Chemical fertilisers can be formulated and purchased for pretty much every aspect of plant growth, unlike organics which are in general "broad spectrum"

It is important to remember that with both "organic" (composting) fertilizers as well as "synthetic" fertilizers can be prone to leaching. In fact it is the nutrient itself which can move through the soil profile. N (nitrogen) is highly mobile in soil solution, therefore it is the nutrient that is focused on the most when people refer to leaching. The more common nutrients for plant growth (macro nutrients); Nitrogen, Phos, Potassium, Sulfur are only available to to plant when in soil solution, however.

*Eutrophication can result due to large amounts of N reaching water ways that can carry it to lakes and ponds. Eutrophication is a ruesult of nutrients allowing algae to grow at an increased rate. The increase in algae and the respiration of the plants reduces the oxygen level in the body of water producing negative effect for the flora and fauna.

The following is a brief comparison between Organic and Chemical fertilisers:

Organic: Cheap to produce - bulky

Chemical: Medium to expensive to produce - concentrated

Organic: Medium ease of application, but need to use a lot

Chemical: Easy to apply, concentrated so you use less product

Organic: Can not improve soil structure but, can increase organic matter levels which can increase soil fauna and CEC (cation exchange capacity) in the upper root zone

Chemical: No improvement to soil structure, products are just as easily leached

Organic: Many can be smelly because of the source of the raw material

Chemical: Most dry fertilizers have little or no smell

Organic: Very little chance of over-fertilising or fertiliser burn

Chemical: Products have to be used with care as they are concentrated and can burn plant foliage or roots if applied incorrectly.

Organic: Most products provide a number of side benefits such as micro-flora and "good" bateria when added to the soil

Chemical: No micro-flora or bacterial content

For home and garden use, organic or composted forms of plant nutrients are very good choices. There are very few negative aspects of organic nutrient usage, and the drawbacks there are can usually be overcome with a change in mindset. Composts, take time, and can be somewhat labor intensive not only to make, but to apply. Organic materials used for nutrients are usually "worked" into the soil rather than spread on top, in an area with hillsides or a decent slope this "tillage" can increase the loss of topsoil through water erosion. The smell is easy enough to deal with when looking at organic fertilizers, the decomposition of the organic material producing that smel is actually part of the process of making plant available nutrients. It does take a lot of material to provide enough plant nutrients when growing nutrient intensive plants, and the "analysis" of the nutrients in a compost are extremely variable.

Chemical fertilizers can be used as stand alone products or even to supplement organic fertilization. Chemical fertilizers can be crop/plant specific, including macro and micro nutrients in an almost unlimited number of blends. Not just as a percentage in the analysis of N-P-K but, often N-P-K-S-Cl and micro nutrients such as zinc and boron, etc. In Agricultural crops such as wheat and corn NH3 (Anhydrous Ammonia) is the most common fertilizer, it is 82% N and an efficient way to provide adequate nutrients for the growing season. NH3 is usually applied in a 'band' below the soil surface, near where the seed will be planted. It is common applied with a 'band' of liquid fertilizer including liquid forms of nitrogen, sulfur, potassium, phostphate, chloride, etc. The fertilizer mix is developed after taking into consideration, the crop to be grown and the soil sample analysis. Many growers also use liquid forms of N that include Aqua ammonia (about 27% N) and UAN-32 (a urea based fertilizer that is about 32% N)

Common types of mid-season fertilizers or top-dress fertilizers are dry prills which are broadcast over a field, and rained or irrigated into the soil. Also UAN-32 and other liquid fertilizers can be mixed in a spray solution and applied to a growing crop for both foliar as well as soil uptake.