CHELATES AS AIDS IN COMBATING PLANT MALNUTRITION 
Organic chemicals known as chelates(pronounced kee-lates) are rela- 
tively new aids to plant growers in protecting plants against deficiencies 
of certain metal nutrients, notably iron and zinc. The most characteristic 
distress sign of a plant deficient in one of these metals is a yellowing and 
fading of foliage. This symptom, termed chlorosis, indicates that the 
plant is developing too little of the vital green coloring material, chloro- 
phyll. 
Iron and zinc deficiencies in plants are common causes of low yields 
and other disappointments to growers--not because the soil is necessarily 
lacking in iron or zinc, but because the metal is in a form not readily 
available to plants. Older methods of treating metal-deficient plants have 
been only partly successful. Chelates offer a new approach to combating 
this type of plant malnutrition, with Some distinct successes already to 
their credit. 
The name chelate was coined from the Greek word "chela, '' meaning 
claw, to describe chemicals(both natural and synthetic) that have a pecul- 
iar capability of enveloping certain elements. This claw-like grip is actu- 
ally an electrical force. When the right chelate is combined with a metal, 
such as iron, the electrical force causes the metallic particles, known as 
ions, to remain soluble in water and protects them from further chemical 
and physical changes. Metals in water-soluble form are most readily 
available to plants for nutritional use. 
Natural chelate materials occur in soils, but they are sometimes not 
sufficiently stable, effective, or abundant enough to keep some nutrient 
metal in soluble form for plant needs. The chelates that are being used 
in agriculture are relatively stable synthetics made from organic com- 
pounds. A successful chelate treatment is shown in Figure 1. 
Prior to the 1950's, synthetic chelates were most familiar tochemists 
who required a metal-stabilizing agent in certain analytic and industrial 
processes. Some efforts were made to apply these chemicals to plant re- 
search but results were not encouraging. 
The first strong evidence that synthetic chelates would be useful to 
agriculture was presented in1951 when scientists at the University of Cali- 
fornia reported that application of a chelate combined with iron (chelated 
iron) could overcome iron deficiencyin plants grown in a nutrient solution. 
Shortly thereafter, practical field use was demonstrated by scientists of 
the Florida Citrus Experiment Station who applied chelated iron to citrus 
trees, with strikingly good results, to correct a mineral imbalance that 
damaged trees on acid sandy soils. 
Spec 
