bio world: Fertilisers and Manures

Fertilisers and Manures

Fertilisers and Manures
Contain one or more essential elements and are added to land to encourage crop growth.
Amounts added are decided after a soil test.
Fertilisers are manufactured materials and are inorganic.
Manures are animal and plant wastes and are organic.

Fertilisers
Most fertilisers in Ireland contain N, P & K either singly or in combination.
Fertilisers containing one nutrient element are called straights or simple fertilisers.
Fertilisers containing two or more nutrients are called compound fertilisers.

Straight Fertilisers
Most common is Calcium Ammonium Nitrate (CAN) which supplies nitrogen as ammonium (13.75%N) and nitrate (13.75%N). It is used on crops that need nitrogen immediately.
Urea (46%N) is also a form of nitrogen but as it has to be converted to ammonium and then nitrate before it is available to plants it does not give as quick a response as CAN. It can volatilise into ammonium gas and be lost from the soil in warm dry weather so only spread in moist conditions.

Straight Fertilisers cont.
Ground rock phosphate (14.5%P) is used in forest tree fertilisation. This is because the acid nature of the soils that the trees grow on dissolves the phosphate and make it available over a long period.
Sulphate of potash is used in potato production to give a more floury potato.

Compound Fertilisers
Compound fertilisers usually contain at least two of the mineral nutrients, N, P and K.
They are labelled with three numbers to represent the percentage of N, P and K in the fertiliser.

Fertiliser Application
1.Placed in the soil in a band beside a line of seed. Done using a potato planter or combine drill.
2.Broadcast onto the soil surface and mixed through the seedbed using cultivation equipment.
3.Top dressing, where it is broadcast onto a growing crop.
Fertilisers are sold in granulated form to allow more accurate spreading and to reduce their ability to absorb water (results in less caking and blockages).

Organic Manures
Farmyard Manure (dung) contains faeces, urine and bedding and therefore has high organic matter content. This organic matter contributes to soil structure and supplies plant nutrients.
Amount of nutrients are low and they are released over time.
Slurry comes from slatted houses and may be diluted by rainwater collected from yards.
Similar to FYM but with less organic matter. As with FYM there are disease and pest risks associated with spreading slurry

Soil Index System
The soil index system ranks a soil by its fertility and its likely response to fertiliser application
The pH of the soil and the level of nutrients needed to grow a crop are also taken into account.

Farmyard Manure
Consists of animal dung, animal urine and straw from winter bedding.
As the manure rots and decomposes it releases nutrients.
It contributes to soil structure and organic matter.
It is a bulky fertiliser as nutrient content is quite low.

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