Lime, when applied to soils, corrects acidity and promotes plant growth.
Aluminium Toxicity
Aluminium becomes available in acid soils. It stunts plant roots and reduces growth and persistence of pastures and crops. In addition, aluminium toxicity reduces options for the types of crops and pastures that we can grow in acid soil.
How does aluminium toxicity affect plant growth?
Aluminium has a toxic effect on plants by reducing root structure and functioning. The reduction in root growth reduces the plant’s ability to take up nutrients from the soil and stunted plant growth occurs. Because aluminium tends to “tie up” phosphorus in the soil, the plant begins o show symptoms of phosphorus deficiency as well. In addition, plant water use is reduced and perennials fail to persist because of reduced root access to subsoil moisture.
Some plants are more affected by aluminium than others.
Aluminium tolerance Species
| Highly sensitive: | lucerne, barley |
| Sensitive: | phalaris,canola,wheat |
| Tolerant: | sub. clover, white clover, ryegrass, fescue |
| Highly tolerant: | cocksfoot, oats, triticale, lupins |
Aluminium is Measured in 3 Ways
1. Aluminium (mg/kg) using potassium chloride extractant (Al mg/kg KCl)
2. Aluminium using a calcium chloride extractant (Al mg/kg CaCl2)
3. Aluminium as a percentage of cation exchange capacity (Al ex%)
The following table summarizes the critical concentrations of aluminium that will cause a reduction in plant yield:
| Aluminimum tolarance of plants | Aluminium
mg/kg KCl |
Aluminium
CaCl2 |
Aluminium
ex% low salt (0.07 dS/m) |
Aluminium
ex%medium (0.07-0.23) |
Aluminium
ex% high (above 0.23) |
|---|---|---|---|---|---|
| Highly sensitive: | 15-30 | 0.5 | 9-16 | 2-8 | 0.5-2 |
| Sensitive: | 30-50 | 2-4 | 16-21 | 8-12 | 0.5-2 |
| Tolerant: | 50-100 | 4-8 | 21-32 | 12-21 | 6-10 |
| Highly tolerant: | above 100 | 8-13.5 | 32-43 | 21-30 | 10-16 |