Various nutrients are needed in the development of plants. These nutrients are naturally present in the soil. However, if some of these nutrients cannot be taken, the plants have developmental problems. In order to obtain abundant and high quality products from the soil, the missing nutrients must be supplemented with fertilization. However, fertilization activities should not be haphazard and the required substances should be given in sufficient amounts and in a plan.

Phosphorus is one of the essential elements for the growth of micro-organisms. Phosphorus is the basic building block of plant genes and chromosomes. A number of physiological functions such as energy storage and transport of nutrients in plants are carried out by means of phosphorus. Phosphorus increases flowering and fruit formation, accelerates ripening and provides root formation. Phosphorus requirements of plants are generally less than one percent of dry weight. Phosphorus is found mostly in the seeds and fruits of plants. The most important effect in phosphorus deficiency is that the roots of the plants do not develop and fall out of their fruits. Excess phosphorus prevents the intake of potassium, iron, calcium, copper and zinc.

Plants make use of inorganic phosphates dissolved in soil water. In order for plants to benefit from organic phosphorus in the composition of organic wastes in the soil, the degradation of organic substances is required.

In the phosphorus analysis carried out by accredited laboratories in the context of soil measurements, laboratories use different methods such as lysis methods or colorimetric methods. In general, the path followed in these methods is two-stage. First, the suitable phosphorus in the soil is separated and converted into dissolved orthophosphates. Colorimetric measurements of these separated orthophosphates are then performed.

In addition to the legal regulations, the authorized laboratories take into account the published national and international standards. The methods used by the authorized laboratories in phosphorus analysis are as follows:

• TS 8338 Soils - Determination of Phosphorus (Modified Bray and Kurtz No.1 Method)
• EPA 200.7 ICP-OES method