Dave
01-25-2006, 03:22 AM
The aim when attempting to adjust soil acidity is not so much to neutralise the pH as to replace lost cation nutrients, particularly calcium. This can be achieved by adding limestone to the soil, which is available in various forms:
Agricultural lime (ground limestone or chalk). These are natural forms of calcium carbonate which are extracted in the UK from areas such as the Mendips and Salisbury Plain. This is probably the cheapest form of lime for gardening and agricultural use and can be applied at any time of the year. These forms are slow reacting, thus their effect on soil fertility and plant growth is steady and long lasting. Ground lime should be applied to clay and heavy soils at a rate of about 500 to 1,000 g/m² (1 to 2 lb/yd²).
Quicklime and slaked lime. The former is produced by burning rock limestone in kilns. It is highly caustic and cannot be applied directly to the soil. Quicklime reacts with water to produce slaked, or hydrated, lime, thus quicklime is spread around agricultural land in heaps to absorb rain and atmospheric moisture and form slaked lime, which is then spread on the soil. Quicklime should be applied to heavy clays at a rate of about 400 to 500 g/m² (0.75 to 1 lb/yd²), hydrated lime at 250 to 500 g/m² (0.5 to 1 lb/yd²). However, quicklime and hydrated lime are very fast acting and are not suitable for inclusion in an organic system. Their use is prohibited under the standards of both The Soil Association and the Henry Doubleday Research Association.
Calcium sulfate, known as gypsum can be used to amend soil acidity and is also useful for lightening the structure of heavy clays. Gypsum can be purchased or can sometimes be obtained from old domestic plaster. The pH of an alkaline soil is lowered by adding sulfur, iron sulfate or aluminum sulfate, although these tend to be expensive, and the effects short term. Urea, urea phosphate, ammonium nitrate, ammonium phosphates, ammonium sulfate and monopotassium phosphate also lower soil pH.
Agricultural lime (ground limestone or chalk). These are natural forms of calcium carbonate which are extracted in the UK from areas such as the Mendips and Salisbury Plain. This is probably the cheapest form of lime for gardening and agricultural use and can be applied at any time of the year. These forms are slow reacting, thus their effect on soil fertility and plant growth is steady and long lasting. Ground lime should be applied to clay and heavy soils at a rate of about 500 to 1,000 g/m² (1 to 2 lb/yd²).
Quicklime and slaked lime. The former is produced by burning rock limestone in kilns. It is highly caustic and cannot be applied directly to the soil. Quicklime reacts with water to produce slaked, or hydrated, lime, thus quicklime is spread around agricultural land in heaps to absorb rain and atmospheric moisture and form slaked lime, which is then spread on the soil. Quicklime should be applied to heavy clays at a rate of about 400 to 500 g/m² (0.75 to 1 lb/yd²), hydrated lime at 250 to 500 g/m² (0.5 to 1 lb/yd²). However, quicklime and hydrated lime are very fast acting and are not suitable for inclusion in an organic system. Their use is prohibited under the standards of both The Soil Association and the Henry Doubleday Research Association.
Calcium sulfate, known as gypsum can be used to amend soil acidity and is also useful for lightening the structure of heavy clays. Gypsum can be purchased or can sometimes be obtained from old domestic plaster. The pH of an alkaline soil is lowered by adding sulfur, iron sulfate or aluminum sulfate, although these tend to be expensive, and the effects short term. Urea, urea phosphate, ammonium nitrate, ammonium phosphates, ammonium sulfate and monopotassium phosphate also lower soil pH.