Organic vs Inorganic

A fertiliser is any natural or manmade substance that improves the growth of plants and the fertility of soils. It can be organic or inorganic and contains chemical elements that provide one or more essential nutrients to plants. Fertilisers supply in varying but specific amounts the three major plant nutrients N-P-K (Nitrogen, Phosphorus and Potassium). Some fertilisers provide the secondary plant nutrients Ca, S and Mg (Calcium, Sulphur and Magnesium) and sometimes include trace elements which also have a role in plant nutrition (e.g. boron, chlorine, manganese, iron, zinc, copper and molybdenum).

Plants require nutrients for growth. Often our soils do not contain nutrients in the quantities required for optimum plant growth. This can be for a range of reasons but is frequently due to nutrient depletion caused by the removal over time of plant and animal products and by leaching or by gaseous loss.

These nutrients have to be replaced and this is done by applying fertiliser to the soil or in some cases, to plant foliage.

Before choosing a product, you need to understand the choices available and their functions as both Organic and Inorganic fertilisers provide plants with the nutrients needed to grow healthy and strong but every fertiliser contains different ingredients and supplies these nutrients in different ways. So, determining which is better for your plants depends largely on the needs of your plants and your preferences in terms of Cost and Environmental Impact.

 

1/. Organic Fertilisers

Organic fertilisers (animal wastes and plant residues) must be broken down into inorganic forms in the soil before plants can take up the nutrients required for growth and reproduction. Organic fertilisers contain low concentrations of nutrients and may require large volumes of material or other beneficial enhancers such as Humic/Fulvic acids and Biological micro organisms to be broken down into inorganic forms and become available to plants, as well as improve and enhance Soil Organic Carbon (SOC). Organic fertilisers work over time to create a healthy growing environment and can be applied directly to the soil or as a foliar spray, by itself or mixed with fertilisers/chemicals

2/. Inorganic Fertilisers

Inorganic fertilisers have a high concentration of nutrients that are available for plant uptake and are derived from non-living sources. In mineral fertilisers, the nutrients are inorganic chemicals, obtained by extraction and/or manufactured through chemical processes, e.g. the artificial synthesis of ammonia which can then be used to manufacture urea and ammonium nitrate and the reaction of sulphuric acid on rock phosphate to make superphosphate.

Relatively small quantities of inorganic fertilisers are required and transport and application costs are low. Inorganic fertilisers can be formulated to apply the appropriate ratio of nutrients to meet plant growth requirements. Today a wide range of inorganic fertilisers are still required to maintain soil fertility and sustainable agricultural systems.

3/. Mineral Fertilisers

Mineral fertilisers are essentially a combination of naturally occurring fine mineral ores which can contain many essential multi nutrients e.g. P.K.Mg, Ca,Si and Trace Elements. They are not treated with acid and are used in blends.

 

Considerations

• Organic fertilisers are the environmentally friendly choice of the two.
• Inorganic fertilisers cause pollution of ground water, stripping of soil nutrients, plant and root burn if utilized improperly.
• Inorganic fertilisers also do little to contribute to the health and vitality of the soil structure.
• The continual use of inorganic fertilisers reduces the soil’s resistance to pests and diseases over time, killing off the natural microbial activity.

 

Fertiliser Composition

Fertilisers supplement the soil with macronutrients needed in large amounts: nitrogen, phosphorous and potassium (NPK).

Organic and Inorganic fertilisers do so via different materials by nature of there composition:

• Organic fertilisers contain only plant- or animal-based materials that are either a by-product or end product of naturally occurring processes, such as manures, leaves, and compost.
• Inorganic fertiliser, also referred to as synthetic fertiliser, is manufactured artificially and contains minerals or synthetic chemicals.

EG:, synthetic nitrogen fertilisers are typically made from petroleum or natural gas. Phosphorus, potassium and other trace elements in inorganic fertilisers are often mined from the earth. Balanced inorganic fertilisers, high in all three macronutrients, commonly include products like ammonium nitrate, ammonium sulfate, potassium chloride (potash), triple superphosphate, and magnesium sulfate (Epsom salts).

Complete vs. Balanced - Inorganic fertilisers come in single-nutrient or multinutrient formulas. Multinutrient formulas include complete and balanced fertilisers, which contain basic nutrients, such as nitrogen, phosphorus and potassium, as well as secondary and micronutrients such as calcium, magnesium, boron and manganese. The percentage of nitrogen, phosphorus and potassium contained in both complete and balanced fertilisers is indicated by three numbers on the package. For example, a 5-10-5 formula is a complete fertiliser, containing 5 percent nitrogen, 10 percent phosphorus and 5 percent potassium. Balanced fertilisers are those that contain equal nutrient amounts, such as a 10-10-10 formula.

Slow-Release and Specially Formulated - Other types of inorganic fertilisers include slow-release formulas. These formulas contain larger molecules that are coated, helping them to break down slowly in the soil. A typical slow-release fertiliser releases nutrients over a period of 50 days to a year, reducing the chance of burning the plant or root system. Specially formulated inorganic fertilisers are those that are created for a specific type of plant. These special formulas include plant foods for azaleas, rhododendron or roses. Specially formulated fertilisers are usually highly acidic and should be used only on the plants for which they are indicated.

Nitrogen fertilisers - Inorganic nitrogen fertilisers come in many different forms, such as ammonium nitrate, potassium nitrate, calcium nitrate and urea. These fertilisers contain high levels of nitrogen, one of the most vital nutrients for plant growth. However, these inorganic fertilisers tend to increase the pH of the soil upon application, increasing the chances of burn and damage to seedlings. Others pull moisture from the air, making them difficult to apply and store.

Potassium fertilisers - Inorganic potassium fertilisers include potassium sulfate and potassium nitrate, as well as muriate of potash, also known as potassium chloride. Muriate of potash is the most commonly used potassium fertiliser. In some cases, plants may be sensitive to chloride. If a plant is sensitive to chloride, potassium sulfate, also known as sulfate of potash, is a better choice, as it does not contain chloride. Potassium nitrate is easy to apply, because it does not pull moisture from the air, but it does slightly increase the pH of the soil upon application.

Phosphorus fertilisers - Inorganic phosphorus fertilisers such as rock phosphate remain in the soil years after the initial application. Rock phosphate works only in acidic soils, as the nutrients do not break down for plants in neutral or alkaline soils. Superphosphates are other forms of phosphorus fertiliser. These do not affect the pH of the soil upon application, while ammonium phosphates come in water-soluble, granular forms.

 

Nutrient Availability

Organic fertilisers release nutrients only when the soil is warm and moist, which tends to correspond with your plants’ times of greatest need. Organic fertilisers do rely on soil organisms to break down organic matter, so nutrients are released more slowly than they are from inorganic fertilisers. This slow-release method reduces the risk of nutrient leaching, but it takes time to supply nutrients to plants.

In contrast, Inorganic fertilisers provide this nutrition in plant-ready form immediately. However, the concentration of nutrients increases the risk of burning the plant, and the rapid release of nutrients may leach them deeply into the soil and water table where plants can't access them.

Application

The nutrients and exact elements available from an organic fertiliser, such as manure or compost, can only be guessed at without laboratory testing. This means you’re giving an inexact application that may or may not meet your plants’ needs. By comparison, applying inorganic fertilisers is simple, because the amount of a given element and the rate of application are known.

Cost

Organic fertilisers often cost significantly more than inorganic fertilisers, but over time, this extra cost may be outweighed by the benefits it provides. Organic fertilisers continue to improve the soil long after the plants have taken the nutrients they need. Therefore, the longer your soil is fed with organic fertilisers, the better its composition and texture. So, while inorganic fertiliser is cheaper in the short term, it adds less to the soil in the long term.

Environmental Impacts

Inorganic fertilisers are immediately available to your plants, but they are subject to leaching, a process that occurs when fertilisers are washed by rain or irrigation water below the level of plant roots. Heavy applications can burn your plants and build up toxic salt concentrations in the soil, which can create chemical imbalances. Organic fertiliser may also build up concentrations of some nutrients, but buildup of toxicity is unlikely as long as the organic material is able to fully decompose. Organic fertilisers are made from natural sources, only limited amounts of fossil fuels are used in production. This means greenhouse gas released into the atmosphere is lower in organic fertiliser production than it is in inorganic fertiliser production.