Crop Needs
Each crop needs a different range of nutrients at every critical stage of its development. For example, nitrogen and phosphorous are often more critical at early stages of growth to fuel root and leaf development, whereas zinc and boron are important during flowering. Cereal crops use nutrients for growth, progressively moving them from the roots, leaves and stems into the ear prior to the dying off and harvesting of the grain.
Tree crops have different nutrient requirements than field crops. They can store nutrients like nitrogen within their trunk, branches and leaves and then redistribute them at key points during the growth cycle. It is important, however, to supply trees with replacement levels of the nutrients removed in the harvested fruit and those that are critical for growth but can’t be recycled.
Major Nutrients
Major nutrients, nitrogen (N) is often required in the greatest quantity by crops, primarily for vigor and yield. Nitrogen plays a key role in chlorophyll production and protein synthesis. Chlorophyll is the green plant pigment responsible for photosynthesis.
Phosphorus (P), is a vital component of adenosine triphosphate (ATP) which supplies the energy for many processes in the plant. Phosphorus rarely produces spectacular growth responses, but is fundamental to the successful development of all crops. Potassium (K) is needed by virtually all crops and often in higher rates than nitrogen. Potassium regulates the plant’s water content and expansion.
Micronutrients
Micronutrients reinforce and supplement the strong plant growth and structures provided by major and secondary nutrients. Most micronutrients influence growth. For example, manganese (Mn), iron (Fe) and copper (Cu) all influence photosynthesis, the process whereby plants use sunlight for growth.
Iron deficiencies are common – for example in seed fruits – where the effect is to reduce production of chlorophyll. As a result, crops struggle and younger leaves develop a severe yellowing or chlorosis. Boron (B) is needed for the development of shoots and roots, and is essential during the flowering and fruiting phases of crops. Zinc (Zn) is needed for the production of important plant hormones, like auxin. Zinc deficiency leads to structural defects in leaves and other plant organs. Molybdenum (Mo) is involved in plant enzyme systems that control nitrogen metabolism.
