Calcium

Abstract

Two liming treatments were compared against an unlimed control in a field experiment with ‘Valencia’ orange (Citrus sinensis (L.) Osbeck) trees planted on a deep acid sand. The two 1ime treatments were: 1) dolomitic limestone (DL) applied as needed to maintain soil pH 7, and 2) combinations of calcitic limestone (CL) and gypsum (G) to maintain pH 7 and to provide, annually, a total of 224 kg added Ca per ha. The experiment started when the trees were 2 years old and continued for 15 years. Trees on the limed plots produced significantly higher fruit yields in 10 of 11 crops. Fruit production increased steadily throughout the period in direct relation to increases in tree size with little tendency to level off. Trees on the limed plots increased canopy volume twice as fast as trees on the unlimed plots where the soil pH remained at approximately 5.0. Tree growth and fruit yield responses to liming were very similar for both lime treatments. Liming reduced the concentrations of N and K in the leaves, while increasing Ca. Leaf Mg concentrations were increased by DL and reduced by CL/G. The CL/G treatment increased the concentration of leaf S.

Key words:

• Dolomitic limestone
• gypsum
• limestone
• soil acidity