The diagram shows a darkened top soil and reddish
subsoil layers that are typical in some regions
A Soil Test Kit
Spreading Manure, an Organic Fertilizer
| The Soil|
The quality and feed value of grasses grown on a field is dependent on the right balance of nutrients in the soil. To determine which nutrients are absent from the soil it will need to be tested. Soil testing kits are available from garden centres to test the level of acidity and the Agricultural Advisory Service can advise about soil testing for nutrient deficiencies.
Nutrients present in soil include:
Phosphorus is necessary to ensure good root development. If it is absent from the soil it can be applied in the form of phosphates. Phosphate promotes the growth of clover but too much clover makes the grazing too protein rich for horses and too much phosphorus inhibits the horse's ability to utilize the calcium in his diet, therefore horse pasture must not be overdosed with quick acting phosphate.
Nitrogen is mainly added to soil during the growing season as it is washed through the soil by rain. Clover supplies nitrogen to the soil due to bacteria present in nodules on the roots. These bacteria can convert atmospheric nitrogen into organic nitrogen compounds.
Calcium levels are maintained through the application of lime to the soil. Lime reduces acidity therefore enabling nitrogen, phosphorus and potassium to be release from the soil as well as increasing the breakdown of humus by soil bacteria. Extra calcium in the soil is known as FCC (Free Calcium Carbonate) and soils that are rich in FCC never need to be limed.
Clay and loam soils usually have potash present in higher levels. It is released slowly from the clay and is needed at root level to promote the growth of grass. If hay crops are regularly taken from land, potash will need to be applied.
Well drained soil allows oxygen to mix within the soil particles. This helps root growth and the breakdown of organic matter, therefore releasing nutrients into the soil. Well drained soil warms up more quickly and grass will begin to grow earlier and stronger. If fields are not naturally well draining, you should seek expert advice regarding artificial drainage.
There are three different categories of fertilizer; organic, semi-organic and inorganic.
Organic fertilizer is produced from substances derived from living organisms and natural resources such as manure, slurry, peat, seaweed, blood and meat meal. As the materials break down the nutrients are slowly released thus enriching the soil.
Semi-organic fertilizers are the most preferable choice to be used on land that horses will graze on. They are in pellet or granule form and they consist of an organic base mixed with inorganic nutrients. They provide nutrients into the soil slowly whilst promoting soil micro-organisms.
Semi-organic fertilizers do not need to be applied as often as inorganic fertilizers because as they have a slow nutrient release rate they are less prone to leeching, therefore reducing wastage and proving to be more economical.
They also help to improve the aeration of the soil as the promotion of micro-organisms helps to encourage earth worm activity.
There are many different types of fertilizers available on the market. Straight Fertilizers provide one main nutrient while compound fertilizers provide several.
On the bag of compound fertilizers, reference is made to the amounts of nitrogen, potassium and phosphorus in the product. For example, 20:10:10 contains 20 units of nitrogen, 10 units of potash and 10 units of phosphate.
The nitrogen present in fertilizers is usually a natural by product of coal gas in the form of ammonium sulphate. Phosphates are salts or chemical compounds derived from phosphorous and they are usually obtained from rock sources. Potash is any of the salts derived from the metallic element potassium.
Before fertilizer is applied the field must be harrowed to loosen off dead grass and soften the top soil. The machinery used to spread the fertilizer depends on the type of fertilizer being used but a farmer or contractor will be able to advise you.
After application of the fertilizer, the fields must be rested for at least a fortnight to allow the fertilizer to break down. A few showers of rain will help to speed up the process, then you can safely turn horses back onto the pasture.
Ground Limestone is the commonest source of calcium carbonate for fields. It is easy to work with and it has a high neutralizing value.
Ground chalk also has a high naturalizing value but as it needs to be dried before it is ground, it is slightly more expensive than limestone.
Calcified seaweed is available in granule or powder form and it contains trace elements and minerals. It is easy to work with and horses can graze immediately after it has been applied.
Lime should be applied when the land is dry so the lime particles can settle directly on the soil and the machinery used to apply it doesn't cut up the pasture. Harrowing will help to mix the lime into the soil and ensure you keep horses off the land until the lime has been washed into the ground by the rain.