ABSTRACT

Calcium, magnesium, sulfur, and chlorine, along with nitrogen, phosphorus, potassium and sodium, are the eight most-abundant elements taken up by plants from soils. Magnesium is a constituent of chlorophyll and is readily transported within plants. When an Mg deficiency occurs, the oldest or lower leaves will show a yellowing. Chlorine was one of the last elements found to be essential. The plant requirement for CI is very small and it is very difficult to develop an environment free of CI for growing plants. During fruit development, this condition aggravates Ca deficiency in some crops, like tomato and watermelon, during the fruit development period. Other crops, including peanuts and celery, may show Ca deficiency when grown on soils that supply adequate Ca for many other crops. Atmospheric deposition of S is quite variable but usually in the range of 3 to 12 kg/ha in the US.