ORGANIC OR INORGANIC?: The choice between organic and inorganic fertilisers depends on the gardener and needs of the garden.
FEEDING your plants well is essential if you wish to enjoy a healthy garden full of greenery and flowers. This week I will focus on what you can give your plants to help them thrive.
Basic nutrients
N: Nitrogen aids in nucleic acid, amino acids and chlorophyll formation. It is a mobile element that tends to move from older leaves to the formation of new leaves. Thus yellowing in older leaves indicates a shortage of N, if the younger leaves are still green.
P: Phosphorus is important for cells or the tree will bear less and smaller fruits. Without P, roots do not grow well and even vegetative growth stops.
K: Potassium is an enzyme activator and can prevent some diseases. It helps plants withstand droughts and gives them resistance against diseases.
Ca: Calcium is for the formation of cell walls. A lack of this element causes rolled leaves and flower tips will rot.
Mg: Magnesium is necessary for chlorophyll production. A lack of magnesium will cause general yellowing of the foliage.
S: Sulphur is part of protein synthesis, chlorophyll formation and nitrogen fixation efficiency.
Cl: Chlorine is good for the prevention of diseases.
Several others micro elements like boron, manganese, copper, molybdenum, iron and zinc are equally important in agriculture.
There is still debate on whether organic or inorganic fertilisers are more appropriate for your garden.
Plants on a strict diet of organic fertilisers are not necessarily healthier than those fed with manufactured fertilisers. The nutritional value of the feed is affected by the amount and content and not by the source of the nutrients.
Organic fertilisers
Fertilisers produced from organic materials contain carbon, nitrogen, phosphorus and potassium. Organic fertilisers are derived from animal manure, compost, sewage sludge and by-products from processed plant and animal materials.
The advantage of using organic fertilisers is that they naturally contain organic matter and this is beneficial to plants and soil. Organic matter helps to improve the water-holding capacity of soil and augments its structure. The other advantage is the increase of microbial activity and even earthworms, which increase the breakdown of other sources of bonded nutrients in the soil for the plants. The action of the microbes would reduce contamination in the soil.
A disadvantage of organic fertilisers is that they have lower nutrient content. This means more material has to be applied depending on their source of organic content. The slow release of nutrients in organic fertilisers can have a detrimental effect on crops for fast turnover and may result in malnutrition. Organic sources like fish meal and manure can also be smelly.
Inorganic fertilisers
Inorganic fertiliser is mainly manufactured from synthetic mineral or natural substances of nitrogen, phosphorus and potassium. Nitrogen from the air (78 per cent) is used for making urea by combining methane gas under pressure. This converts into anhydrous ammonia – a basic constituent in urea.
Inorganic fertilisers are widely available in various compositions. Keep yourself informed about inputs in NPK content percentages. The essential elements of NPK are expressed as 12-12-17+2 meaning it has 12 per cent nitrogen, 12 per cent phosphorus, 17 per cent potassium and 2 per cent trace elements. When you add up these numbers, you don’t get 100. This is because the balance is made up of other materials like soil to ensure your application over an area is even. The same applies for liquid fertiliser.
A disadvantage is the acid content of chemical fertilisers such as sulphuric acid and hydrochloric acid, which can cause excessive soil acidity. This may destroy nitrogen fixing bacteria and micro-organisms living in the soil.
At the end of the day, fertilisers are necessary to provide essential food for plants. So it is up to you to choose between organic and inorganic, but be sure to feed your plants according to their nutritional needs.
Happy gardening.