Fertilizers Explained

[gothash]

I would like to take credit for this but credit is due where credit is due. i obtained this info from the Incitec website (although it obtains to agriculture on a large scale, the plant basics and nutrient requirements are basically the same) Feel free to move this to the appropriate section if you feel it isnt in the right place.

 

Nitrogen

 

Nitrogen in soils

Nearly all the Nitrogen in the soil orginates from the atmosphere, which is made up of about 80% nitrogen, The Rocks and minerals from which soils are formed do not contain nitrogen,

Most of the nitrogen present in the soil is in the form of organic matter. Organic Nitrogen is however not available for plant uptake, It must be convereted to simply inorganic forms i,e ammonium and nitrate

Nitrogen can be lost from the soil in various ways, thru Volatization and Dentirification to the atmosphere, and leaching below the root zone following heavy rain.

 

Nitrogen in Plants

Apart from carbon ©, Hydrogen (H) and oxygen, which are derived from air and water, nitrogen is required by plants in greater quantity than any other nutrient. It is one of the most commonly limiting nutrients in any agriculural system. Legumes are able to fix nitrogen from the air, but other plants are reliant on teh soil and or fertiliser for nitrogen

Plant uptake from the soil is mainly available as nitrate although ammonium is also taken up,

Nitrogen is essential in the formation of chlorophyll (the green pigments in plants) which converts sunlight into carbohydrate.

A shortage of nitrogen inhibits plants in the basic functon of trapping energy. Nitrogen is a major constituent of protein. Therefore a shortage of nitrogen not only affects yeild but will affect the over quality of your crop.

 

UREA is the most widely used and available nitrogen fertilzer and at 46% N. it is the most concentrated solid nitrogen fertilzer, can easily be mixed with other forms of fertilisers

 

 

Phosphorus

 

Phosphorus in Soils

Australian Soils are characteristically low in phosphorus in there native state, with the exception of a few soils of basaltic origin and some alluvial soils.

 

Most of the phosphorus in soils is associated with organic matter. Even in mineral soils, between 20% and 80% of the total phosphorus will be present in organic forms.

 

Phosphorus is most available for uptake for plants in the pH range 6.5 - 7.5 at pH below 5.5, slowly soluble oxides of iron, aluminium and manganese form, reducing phosphorus availability, while at pH above 7.0, slowly soluble calcium phosphate is formed

 

Phosphorus in the soil is relativly immobile, Phosphorus applied as a fertilzer rarely moves any great distance in the soil without some form of physical mixing e.g cultivation, the distance that the phosphorus front moves in the soil from fertilzer granues is rarely more than 4-5cm

 

Phosphorus in Plants

Phosphorus is one of the primary nutrients along with nitrogen and potassium it is required in large quantities by plants.

Most plants take up the bulk of there phosphorus requirment early in life. While Phosphorus is not mobile in soils, it is one of the more mobile nutrients in plants. It is readily moved within the plant from old to young tissue. Phosphorus is required for cell division at growing points, and is particulary important in stimulating root development. The best results are best obtained if applied early

 

Potassium in Soils

Potassium is quite abundant in soils, typically ranging from .5 to 4.0% of this, only a small part is present in water soluble and exchangeable forms, and readily available for plant uptake, usually less than 1% of the total.

Sandy soils have the lowest potassium content, while clay and alluvial soils have the highest. However even clay soils can become depleted where considerable quantities are removed. Potassium in the soil solution is suject to leaching. It is more readily leached than phosphorus less so than nitrate nitrogen

 

Potassium in Plants

Potassium is required in larger amounts than any other mineral element, with the exception of nitrogen. In a few crops, potassium uptake exceeds that of nitrogen eg. Bananas

 

Potassium is not a component of any organic compound in plants. It is important in various physiological processes, including photo synthesis the metoblism of carbohydrate and protein, the activation of enzymes and the adjustment of stomatal movement and water relations. Adequate potassium helps reduce lodging, increases winter hardiness and disease resistance, and improve yiels and the quality of the "fruit" Optimum potassium concentrations in plant tissue are usually in the range of 1.5 to 4.5% K on a dry weight basis