Organic Fertilisers VS Manufactured Fertilisers VS Gaseous Fertilisers VS Liquid FertilisersFertilisers are one of the most widely used forms of chemicals in agriculture. Fertilisers are added to the soil in which crops are growing to provide nutrients required by plants. Fertilsers can be divided into categories: organic, manufactured, gaseous and liquid.
Organic FertilisersExamples of organic fertilisers include manure, worm castings, seaweed and sewage. There are also manufactured organic fertilisers that include bloodmeal, bone meal and seaweed extracts.
Organic fertilisers are mainly used on small farms or horticultural farms because they only contain small amounts of nutrients compared to manufactured inorganic fertiliser. They need huge application rates to produce what inorganic manufactured fertilisers can with small application rates. To use organic fertilisers on a broad acre farm would be very costly because the farmer would not be able to produce all the organic fertiliser on his own farm so he would have to buy more in and transport huge amounts of manure to his farm and it would also take a lot of work and time on his tractor to spread it.
Although the amount of nutrients in organic fertilisers are small they have advantages for horticultural growers. They produce some or all of their fertiliser on-site lowering operating costs. The majority of nitrogen supplying organic fertilisers contain insoluble nitrogen and are slow release fertilizers and their effectiveness can be better than inorganic manufactured nitrogen fertilisers. They release nutrients at a slower more consistent rate that helps to avoid a boom-and-bust pattern. Improve the soil structure that helps to retain soil moisture.
Manufactured FertilisersManufactured fertilisers are normally made from petroleum or natural gas. They are usually in high in nutrient content and only small application rates are needed. If the fertiliser is over applied the fertiliser can burn plants. Phosphorus, potassium and other trace element fertilisers are often mined from the earth. Manufactured fertilisers include common products like ammonium nitrate, ammonium sulfate, triple superphosphate, potassium chloride and magnesium sulfate-epsom salts. These products are quick acting even in cool soils and are inexpensive.
Manufactured fertilisers are mainly used on large farms that are usually broad acre because they are cheap and only need small application rates. Manufactured fertilisers are used on small horticultural farm but they don't rely on it because it is cheaper to use organic fertilisers and they are more effective.
The advantages of manufactured fertilisers are only small application rates are needed. Manufactured fertilisers have extremely accurate application rates to match plant production and they are easy to apply and can be applied when the crop is sown.
Gaseous FertilisersFarmers usually hire trained specialists to apply the gaseous fertiliser. Gaseous fertilisers are usually stored in a liquid form under pressure and under refrigeration. It is applied by injecting it into the soil with a special plough with injection knives. The gas is stored in a pressurized tank that sits on top of the plough or is on a separate trailer that trails behind the plough. The plough is pulled by a tractor. When it is applied it quickly vaporizes but is captured by several components in the soil that included water, clay, and other minerals. The depth settings for the knifes are from 10 to 25 centimeters below the ground depending on soil type, soil conditions and spacing of injection knives. The most commonly used gaseous fertilizer is anhydrous ammonia.
The problems with gaseous fertiliser is the unwanted escape of the gas when it is being applied. The gas escapes just before the closing of the furrow when the tyne is ploughing though the ground. Because the plough needs to go so deep into the ground the dry top soil falls into the furrow to resulting in a dry seed bed. This is a big problem for semi-arid farming regions where no-till farming is carried out.
Liquid fertilisersLiquid fertilisers are mainly used for plants that are already grown to reasonable size. The benefit of liquid fertilisers is that nutrients can be applied to a crop when it is established. It can be applied in three ways, sown with a seeder when the crop is seeded, or later with a sprayer when the crop is grown, or through irrigation pivots. Other forms of fertiliser cannot be applied when the crops are established like liquid fertilisers can be, because they damage the crop too much when they are being applied. Liquid fertilizers generally have a quicker release than other fertilisers, so a crop can be saved from dying of nutrient deficiencies a lot quicker.
Soil Nutrient DeficiencyNutrient deficiency symptoms are often the first clues to a nutrient problem in a paddock. Plants which are under stress show unusual growth patterns and colour of the plants. Deficiency symptoms can sometimes be confused with other complex events like high water tables, salt damage, disease, drought, herbicide stress and varietyl of crop differences. Deficiencies can also be so slight that they are confused with other problems.
Deficiency Symptoms of Macro NutrientsNitrogenPlants develop small pale green to yellow leaves and have poor stem and leaf growth.
PhosphorousLeaves are bluish green with purple edges and the plant has very poor root growth.
PotassiumWhite or brown dead spots on leaves. leaves start to die from the base upward.
Soil TestingMicro and Macro NutrientsThe three macro nutrients are nitrogen, phosphorous and potassium.
Micro nutrients include sulphur, calcium, iron, manganese, molybdenum, boron, zinc, chorine, copper, and magnesium.
Acidity and AlkalinityWhen the soil pH is too acidic (low pH) or alkaline (high pH) nutrients present in the soil become locked up or unavailable. Correcting the pH can be done by applying fertiliser because it unlocks plant nutrients in the soil.
pH Description< 5.5=Strongly acid5.5 - 5.9=Medium acid6.0 - 6.4=Slightly acid6.5 - 6.9=Very slightly acid7.0=Neutral7.1 - 7.5=Very slightly alkaline7.6 - 8.0=Slightly alkaline8.1 - 8.5=Medium alkaline> 8.5=Strongly alkalineApplication Rates, Timing and MethodsApplication ratesFor large scale farming application rates are usually measured in kg per hectare and for small horticultural farms application rates are measured in grams per square metre.
TimingMost commonly fertiliser is applied before or when the crop is sown but it can be applied later on when the crop mature by using liquid fertiliser.
MethodsFertiliser can be applied in many ways that include with a seeder that puts the fertiliser in the ground. So when the plant germinates in has plenty of nutrients. A spreader (only way to apply organic fertiliser) that throws the fertilizer across the ground and with a sprayer that uses liquid fertiliser to sprays the fertiliser across the crop.
ConclusionApplication of fertilisers are a very important part of sustainable agriculture. Fertilisers have facilitated great increases in production from the cropping and pastoral industries. Problems arise when excess fertiliser is washed or leached from the farms and ends up in streams and waterways. Excessive use of fertiliser should be avoided.
Farmers should decide what fertiliser to add on the basis of cost effectiveness, availability and how much nutrient plants need. Farmers may get help and advice from local field days and local agronomists.