The main objective of fertilization is maximum yield within the context of environmentally-sound, long-term production. A balance among nutrients in the plant may be more critical than actual amounts, so taking care of the four major elements is not enough for maximum yields. There is a relationship between Mn and Fe, Zn and P, and Ca, Mg, K, and N. Having a basic understanding of the micronutrients is important.

Tests for crop nutrient needs may not show a deficiency but some fertilization may still be needed for optimal results. This range from no visible symptoms of deficiency to top yield is called "hidden hunger". In contrast, there is a point when more fertilization does not produce higher yields and can be a waste of money and possibly environmentally unsound. Producers must evaluate how much fertilization is enough to bring about optimal production.

Calcium is needed for cell elongation and division. It is found in concentration ranges form 0.2 to 1.0%. Magnesium, in concentration levels of 0.1 to 0.4%, is the main component of chlorophyll molecules and therefore critical for photosynthesis. Boron concentrations differ between grasses and legumes; grasses need 6 to 18 ppm, while legumes need 20-60 ppm. Boron is involved in meristem development, pollination, nodule formation in legumes, and translocation of sugars, starches, N, and P. A boron deficiency will become visibly apparent; curled, wilted leaves, discoloration, cracking fruits, tubers, or roots. Iron in concentrations of 50-250 ppm will be involved in oxidation reduction reactions in plants and soils. Manganese concentration levels of 20-500 ppm will be an integral part of photosynthesis. Copper, 5-20 ppm, is involved with enzymes. Zinc, 25-150 ppm, deficiencies will be very visible on plant leaves. Only about 1 ppm of molybdenum is needed by plants for enzyme functions and nitrogen fixation in legumes. Chloride, 0.2 to 2.0%, is a part of photosynthesis and leaf development. It helps plants suppress diseases. Cobalt at 0.02 to 0.5 ppm aids in nitrogen fixation. Sodium, with 0.01 to 10% concentrations, influences water utilization. Silicon concentrations of 0.2 to 2.0% will be a part of root functions and cell wall development. There seems to be relationship between K and Si. Nickel, 0.1 to 1.0 ppm, must be balanced wih Zn and Fe for normal plant functioning. It has a relationship with N.