SLOW RELEASING FERTILISERS
In the modern day commercial agriculture, fertiliser usage has become a prerequisite to ensure crop production. The intervention of chemical fertilisers and growth of fertiliser responsive crops has markedly increased crop yields after the green revolution. Unfortunately, plants cannot uptake a significant amount of nutrients (>50%) from the applied fertilisers, resulting in low fertiliser use efficiency. Leaching, volatilization, denitrification, fixation, erosion, and runoff could result in more than 50% nutrient loss resulting in low fertiliser use efficiency and create environmental pollution as well as a rise in the cost of fertiliser application.
Some of the interventions that minimise or reduce such nutrient losses include precision nutrient management, use of cover crops, following regular crop rotation practices, doing conservation tillage or opting for slow release fertilisers, etc. Among them, Slow releasing fertilisers (SRFs) have been a new concept and let us discuss them in detail in this post.
What are Slow Releasing Fertilisers?
“Slow releasing fertilisers include products in which the nutrients contained within the product are either slowly soluble, slowly released, or held in a natural organic form (which require mineralization and nitrification in the soil)” which in turn make nutrients available to plants gradually over time, instead of all at once.
Slow Releasing Nutrient Fertilisers and their applications in agriculture:
- Nutrient Efficiency: Slow-releasing fertilisers provide controlled and prolonged release of nutrients over an extended period making the crop efficiently utilise the nutrients over a period of time.
- Reduced Environmental Impact: They help mitigate negative impacts on the soil and eventually on the environment that are associated with excessive nutrient application.
- Plant Growth and Health: The controlled release of nutrients from slow-releasing fertilisers provides a steady supply of essential elements to plants. This consistent nutrient availability supports continuous growth, healthier plant development, and improved crop yields.
- Decreased Fertiliser Application Frequency: Slow-releasing fertilisers reduce the need for frequent applications compared to conventional fertilisers thus reducing the amount of fertiliser applied and reduce the risk of over-fertilization or nutrient imbalances.
- Improved Soil Health: By supplying nutrients gradually, they promote better nutrient cycling and retention within the soil.
- Suitable for Specific Crops or Conditions: Slow-releasing fertilisers can be tailored to meet the specific nutrient needs of the crops, allowing for precise nutrient management.
Slow Releasing Nitrogen (N) fertilisers:
Nitrogen is one of the major and very important elements for plant growth and development. However it is highly mobile and leeches quickly leading to environmental concerns such as groundwater contamination and nutrient imbalance in the ecosystems. To address this, researchers have been focusing on developing slow-release nitrogen fertilisers that dissolve slowly into the soil and will be available to the plants for a longer time.
Several methods and technologies used to synthesise slow-release nitrogen fertilisers include:
- Coating: The nitrogen-containing fertilisers are coated with materials that control the release rate of nitrogen. These coatings can be made of polymers, sulphur, neem or other substances that gradually break down or dissolve in the soil, releasing nitrogen slowly.
Eg: Neem Coated Urea, Sulphur Coated Urea,Polymer Coated Urea,Polymer coated AmmoniumNitrate et
- Encapsulation: Nitrogen fertilisers are encapsulated within porous materials or membranes that regulate the release of nutrients. The encapsulation can be done using materials like clay, hydrogels, or biodegradable polymers, which control the diffusion of nitrogen into the soil.
Eg: Urea Formaldehyde, IsobutylideneUrea(IBDU)
- Stabilisation: Certain compounds can be added to nitrogen fertilisers to reduce their conversion to highly mobile forms that are prone to leaching. For example, nitrification inhibitors can be incorporated into fertilisers to slow down the conversion of ammonium to nitrate, which is more susceptible to leaching.
- Controlled-release formulations: These are specialised sets of fertilisers that are designed to release nutrients based on specific environmental conditions, such as temperature, moisture, or microbial activity. These formulations ensure that nitrogen is released when plants require it the most.
Eg: Polymer Coated Urea,Polymer coated AmmoniumNitrate
- Granular nitrogen fertilisers: These fertilisers provide plants with nitrogen in a solid, granular form, and consist of small particles or granules that contain nitrogen compounds, such as urea, ammonium nitrate, or ammonium sulphate.
Govt Interventions in India to reduce N Pollution and enhance it’s utilisation by the crops:
- During 2015, the centre has made it mandatory to coat all indigenously manufactured and imported urea with neem oil which is famously called the Neem Coated Urea.
- Following that in 2018, the centre ordered that all 50 kg Urea Fertiliser bags be replaced with 45 kg bags.
- Later in 2021, IFFCO launched liquid Nano Urea. A Nanotechnology based Agri input which provides N to the plants ,enables better absorption and utilisation of nutrients by plants resulting in high Nutrient Use Efficiency (>80%) .And currently in 2023, PM PRANAM Yojana was launched. It is a Programme for Restoration, Awareness, Nourishment and Amelioration of Mother Earth (PRANAM). This scheme is to incentivise States and Union Territories to promote alternative fertilisers and balanced use of chemical fertilisers. This scheme seeks to reduce the use of chemical fertilisers in the states.
- Under this Yojana, “Urea Gold”, Sulphur coated Urea was introduced. In addition to the slow release of Urea, Urea Gold also addresses Sulphur deficiency of soils which is a major problem in all parts of our country. TSI-FAI-IFA project ( The Sulphur Institute ) (2020) data prove that sulphur deficiencies are a critical problem in 50% of districts of India.
By embracing the use of slow-release fertilizers and implementing appropriate government interventions, we can revitalize soil health, enhance crop productivity, and ensure sustainable agricultural practices. It is crucial for farmers and policymakers to adopt these strategies for a greener and more productive future.