Some crops require more nitrogen than others, some more potassium than others and some more phosphorus than others. The same goes with different types of soils, whose nutrient status may vary from place to place and from time to time. Constant soil sampling and testing is therefore important to keep track of the changes in nutrient composition. A deficiency in phosphorus, for example, would need to be addressed as promptly and as efficiently as possible for the following reasons.
Phosphorus in plants is key in capturing, storing and converting the sun’s energy into biomolecules, such as adenosine triphosphate (ATP), that drive biochemical reactions (like photosynthesis) from germination through the formation of grain or fruits to maturity. Phosphorus is present in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), which store information on how plants should perform routine functions such as synthesizing proteins, lipids and nucleic acid as well as metabolizing sugars. Phosphorus promotes early root growth, winter hardiness and seed formation, stimulates tillering and increases water use efficiency. It therefore goes without saying that root growth is inhibited in the case of a deficiency, whose extreme cases is shown by the leaves turning dark, dull, blue green and pale. Addressing such conditions has to be monitored as an over-application will induce micro-nutrient deficiencies of zinc, magnesium and others with the resultant effect of stunted growth.
Plants that require the phosphates (whose primary sources include manure, compost and phosphate rock) in plentiful amounts are usually those that reproduce and die in one year (lettuce and various legume crops) as well as fruit trees.