Minor Elements

Manganese (Mn) – plays an important role in photosynthesis and chloroplast membrane formation. Needed at only ½ the rate of iron, its importance cannot be understated. Manganese also enters into the chemical reactions of oxidation and reduction. Deficiency – dead (necrotic) spots on younger leaves. Hard and woody stems, slow maturity. It is not very mobile in plants, so younger growth usually exhibits symptoms first. Toxicity – wilting and death in all but small quantities. Note: manganese is toxic in large amounts.

Boron (B) – is needed in small amounts. Boron aids in cell division and in transporting sugars through cell walls. It also aids in forming the amino acids – thymine and cytosine, important to DNA synthesis. Deficiency – affects new growth first. Black, brittle areas on leaf tips. Small, burned leaves with dead spots. Stubby brown and dead root tips. "Heart rot" in beets and "stem crack" in celery. Toxicity – above 10 PPM, dead leaf margins, wilting and quick death of the plant.

Copper (Cu) – is needed in only small amounts. This metal aids in plant metabolism and general health. It helps ward off disease and pests, aids in the utilization of iron and the manufacture of enzymes. Deficiency – dark green, spindly young leaves. Plants are susceptible to disease and insects, wilt easily and exhibit stunted growth. Toxicity – dark roots, leads to an iron deficiency (interveinal chlorosis on young leaves).

Zinc (Zn) – is needed in small amounts for growth and chlorophyll synthesis. Deficiency – short stem internodes and a condition called "little leaf" or "rosetting" where the young leaves are spindly and twist around each other. Reduced or no bud formation. Mottled dead spots between veins. Toxicity – related to an acid pH, splotchy mottled leaves and wilting.

Chlorine (Cl) – this element controls water uptake and transpiration. Stimulates photosynthesis and is a major constituent of the anthocyanin molecule. Deficiency – plants wilt easily. Bronze colored leaves with dead or chlorotic spots, stunted roots with club-shaped tips. Toxicity – saline poisoning, small dark leaves, burned margins and wilting.

Molybdenum (Mo) – a catalyst needed in small quantities. It is involved in nitrogen fixation (assimilation) and in the manufacture of enzymes. Deficiency – causes nitrogen deficiency. Plants are light green, malformed and stunted. Causes the "whiptail" disease where young leaves are long, narrow and severely twisted, but not tightly bunched as in "rosetting" caused by zinc deficiency. Toxicity – very toxic to plants above 100 to 200 parts per billion (not much!). Causes iron and copper lockup and improper nitrogen utilization.

Cobalt (Co) – a constituent of vitamin B-12 and required for the fixation of nitrogen and DNA synthesis. Deficiency – causes pernicious anemia (lack of vitamin B-12) and improper nitrogen assimilation. Toxicity – all but the smallest amount causes quick wilt and death.

What is the NPK and how is relevant to a hydroponic nutrient? The NPK is the ratio of the levels of nitrogen, phosphorus and potassium. Note that the NPK is important in choosing the right nutrient for the proper stage of growth exhibited by your plants.

The nutrient solution in hydroponics, like the in-the-soil solution for traditional soil gardeners, provides the plant roots with water and essential elements. In hydroponics, the essential elements are added to the nutrient solution, using fertilizer (mineral) salts.

There are a number of hydroponic nutrients on the market these days but they mostly fall into one of four categories – they can be either liquids or powders, and these can be either a one or two part formulas. Most hydroponic retail centers offer a wide range of powder and liquid, one and two part, grow and bloom nutrients.

Powder nutrients are more concentrated than liquids and are usually less expensive. Powders should be dissolved in hot water to make a liquid concentrate, and not be used by adding the powder directly to the tank. This should be done to insure that the powder dissolves completely. If a liquid concentrate is to be made from a two-part powder formula, it is essential that the final volume of the two solutions be the same.

Liquid nutrients are more popular with most hydroponic gardeners because they are easier to use. Liquid nutrients can be added directly to the tank, while powders should be mixed separately then added to the tank. Also another thing to remember is that liquids should be shaken well before dilution, to get an even mix of nutrient chemicals by getting the sludge moving.

The strength of a nutrient solution is measured by its electrical conductivity (EC) and is of critical importance. Too high an EC results in vegetative growth at the expense of fruit or flower production and too low an EC produces weak, unproductive plants.

The EC can be expressed as TDS (total dissolved salts) or ppm (parts per million) depending upon the meter that is used. TDS is the concentration of s solution as the total weight of dissolved solids. These meters are widely used by hobbyists, and actually measure the electrical conductivity of a solution. They do this by measuring the amount of electric current a solution carries. The meters use a built-in conversion factor to express the electrical conductivity in TDS/ppm. The conversion factor for true TDS/ppm is expressed as:

True TDS/ppm = 640 x EC (mS/cm)

For example:

EC (mS/cm) x 640 = 640 True TDS/ppm