- Calcium helps to attain better soil structure and drainage.
- Calcium reduces toxicity of certain heavy metals e.g. aluminium and manganese in acid soils.
- Calcium improves the soil environment for micro-organisms e.g. it encourages the growth of nitrogen fixing bacteria.
- Calcium helps to make phosphorus and some micro elements more available.
However, too much calcium can be detrimental for olive production. An oversupply of calcium can inhibit the uptake of potassium, magnesium and trace elements like manganese, zinc and iron. Phosphorus can be locked up by high calcium supply, making the phosphorus unavailable to olive roots.
– calcium, potassium and phosphorus deficiency
– soil crusting
– release of soil nitrogen into the atmosphere
Sodium plays a role in water and pH balance. However the most important aspect of sodium is where we see it in excess supply…salinity. Olives are quite tolerant to saline conditions. Soils can have a high pH if they have high sodium levels. Calcium has beneficial effects to olives under such high pH conditions.
- Light sandy acid soils where the rates of leaching are high
- Soils low in organic matter.
- During drought.
- Soils with high pH (soils that have been too heavily limed).
- Soils that have had a large amount of nitrogen fertiliser.
- Soils that have been heavily cropped
Small leaves, leaf chlorosis and eventual tip necrosis (death of tissue), excessive branching.
Rosette growth of auxiliary buds, limb die back.
Defoliation, distortion thickening.
Cracking, corky blistered stems that may become hollow or brittle.
Poor yield of monkey face fruit (distorted shape) and thickening and twisting of roots which fail to spread properly.
The Importance of Soil pH
What is pH and what does it mean?
pH is a measure of the acidity or alkalinity in the soil. More correctly it is the measure of the potential of Hydrogen ions. The higher the concentration of hydrogen ions in the soil, the lower the pH. The full pH scale extends from 1 to 14 with 7 being neutral. Lower values than pH 7 represent increasing acidity; higher values represent increasing alkalinity.
In practical terms, soils between pH 6.5 and 7.5 are considered neutral; soils in the range 5.6 to 6.0 moderately acid; and below 5.5 strongly acid. The scale is logarithmic, so pH 4 is ten times as acidic as pH 5 and pH 2 is ten times as acidic as pH 3, and so on.
How is pH measured?
Soil pH can be measured in water (pHW) or calcium chloride (pHCA).
It is difficult to compare pH readings in water to pH readings in calcium chloride as the different methods to test the pH of a soil give different results. It is therefore important to take note of the method used.
What is the significance of pH?
Soil pH influences the solubility of nutrients. It also affects the activity of micro-organisms responsible for breaking down organic matter and most chemical transformations in the soil. Soil pH thus affects the availability of several plant nutrients.
Availability of Nutrients
Plant nutrient availability varies quite dramatically with the soil pH. A pH range of 6 to 7 is the most favourable for plant growth because in this range most plant nutrients are readily available.
Soils that have a pH below 5.5 generally have a low availability of calcium, magnesium, phosphorus, nitrogen, sulphur and molybdenum. At these low pH’s, the solubility of aluminium, iron and boron is high; and low for molybdenum.
At pH 7.8 or more, calcium and magnesium are abundant. Molybdenum is also available if it is present in the soil minerals. High pH soils may have an inadequate availability of iron, manganese, copper, zinc, and especially of phosphorus and boron.