Organic fertilisers are defined as fertilisers derived from organic substances, including animal manure and straw. These substances are widely used in agricultural production following specific treatment. In recent years, the trend towards ecological development in agriculture has led to a growing interest in the use of organic fertilisers. They can effectively improve soil fertility and also enhance soil physical and chemical properties, thereby playing a significant role in the sustainable development of agriculture. This paper will provide a detailed discussion of the types of organic fertilisers, their mechanisms of action and their specific benefits in modern agriculture.
I. Types of organic fertiliser
There are numerous varieties of organic fertilisers, which can be classified into the following categories according to their source and the methodology employed in their production:
1. Manure
The term “manure” is used to describe fertilisers derived from animal waste following a process of treatment. Examples of such fertilisers include those derived from chicken manure, cow dung and sheep manure. This type of manure is characterised by a high organic matter content and a rich nitrogen, phosphorus, potassium and other essential plant nutrients profile. Furthermore, manure contains beneficial soil microorganisms that can facilitate the development and growth of plant roots.
2. Stable manure
Stable manure is a fertiliser that is formed through the action of microorganisms, whereby livestock manure and urine are mixed and accumulated with gasket materials such as straw and weeds. It is distinguished by its high concentration of essential nutrients, including nitrogen, phosphorus and potassium, as well as its substantial organic matter and microbial content, which collectively exert a profound influence on soil enhancement.
3. Composting
The formation of compost is a process whereby plant matter, such as crop stalks, green manure, weeds, and so forth, is decomposed by microorganisms. This occurs when these materials are mixed with soil, human faeces and urine, rubbish, and so forth, and then piled together. The distinction between high-temperature and ordinary compost is determined by the temperature at which the fermentation process occurs. The high-temperature composting process is capable of killing germs, insect eggs and weed seeds, and it also results in a faster decay rate and a higher nutrient content.
4. Biogas fertilisation
Biogas fertiliser is the residual fertiliser and water fertiliser that is produced as a by-product of the fermentation of organic materials, such as crop stalks, dung and urine, in a biogas digester. The fermentation process produces biogas, which is then used to generate electricity. The remaining biogas fertiliser is a rich source of nutrients and can be used as a fertiliser for agricultural crops. This type of fertiliser is characterised by a high organic matter and nutrient content, including nitrogen, phosphorus, potassium and other essential elements for plant growth. It has been demonstrated to significantly enhance soil quality and promote plant development.
5. Other organic fertilisers
Additionally, there are specific categories of organic fertilisers, including commercial organic fertilisers derived from industrial by-products such as municipal sludge, kelp residue and sugar residue, as well as mineral fertilisers that are employed as natural fertilisers. The aforementioned organic fertilisers facilitate improvements to soil quality and enhance crop yields.
II. Benefits of organic fertilisers
The application of organic fertilisers not only provides crops with essential nutrients, but also improves the physical and chemical properties of the soil and the ecological environment in a variety of ways.
1. Provision of nutrient enrichment
Organic fertilisers are characterised by a high concentration of nutrients, including nitrogen, phosphorus, potassium and other major elements, as well as calcium, magnesium, sulphur and other trace elements. In comparison to chemical fertilisers, the majority of nutrients present in organic fertilisers exist in an organic state, which cannot be directly absorbed by plants and must be gradually released through microbial decomposition. The gradual release of nutrients not only ensures a continuous supply to the crop but also circumvents the issue of rapid nutrient loss.
2. Improved soil structure
The incorporation of humus into organic fertilisers endows them with favourable colloidal characteristics, which can facilitate the development of a more structured soil matrix and augment the soil’s permeability and capacity to retain water and fertilisers. The enhancement of soil granular structure facilitates the resolution of the contradiction between water, fertiliser, air and heat within the soil, thereby enabling the root system of crops to flourish in an optimal environment.
3. Improvement of soil buffering
The application of organic fertilisers has been demonstrated to enhance the buffering properties of soils, thereby increasing their resilience to fluctuations in acidity and alkalinity. This is of particular importance in soils with an acid-base imbalance, in order to prevent the adverse effects that changes in soil pH can have on crop growth.
4. Increasing soil microbial activity
The microorganisms present in organic fertilisers and the enzymes they produce (such as protease, urease, phosphorylase, etc.) are capable of promoting the conversion of nitrogen and phosphorus in the organic state into the inorganic state, which can then be absorbed by crops. Concurrently, humus in organic fertiliser can form complexes with calcium, magnesium, iron and other soil constituents, thereby reducing the fixation of phosphorus and enhancing its effectiveness.
5. Promoting nutrient transformation
The microorganisms present in organic fertilisers and the enzymes they produce (such as protease, urease, phosphorylase, etc.) are capable of promoting the conversion of nitrogen and phosphorus in the organic state into the inorganic state, which can then be absorbed by crops. Concurrently, humus in organic fertiliser can form complexes with calcium, magnesium, iron and other soil constituents, thereby reducing the fixation of phosphorus and enhancing its effectiveness.
6. Increasing crop yields and quality
The nutrients present in organic fertilisers are capable of providing crops with a continuous and balanced supply of nutrients, which in turn results in the development of well-structured root systems, robust stems and leaves. Concurrently, the provision of adequate trace elements and organic matter can enhance the crop’s disease resistance and diminish the necessity for pesticides. Furthermore, the long-term application of organic fertiliser results in crops of superior quality, enhanced flavour and greater nutrient density.
7. Protection of the environment
The excessive use of chemical fertilisers can precipitate a range of adverse effects, including soil erosion, environmental contamination and soil degradation. In contrast, organic fertilisers represent a sustainable alternative to chemical fertilisers. They facilitate a reduction in the reliance on chemical fertilisers, while simultaneously promoting the recycling of resources through the reduction of agricultural and domestic waste emissions. Additionally, the manufacturing of organic fertilisers, including compost and biogas fertilisers, contributes to the reduction of greenhouse gas emissions and the minimisation of environmental impact.
8. Savings in agricultural costs
The utilisation of organic fertilisers has the effect of reducing the necessity for chemical fertilisers and pesticides, thereby lowering the cost of agricultural production. Concurrently, the nutrients present in organic fertilisers are released at a gradual pace and exert a prolonged influence, thereby reducing the necessity for frequent fertilisation of fields utilising such fertilisers. This also results in cost savings pertaining to both labour and fertilisers.
III. Precautions in the use of organic fertiliser
Despite the plethora of advantages associated with the utilisation of organic fertilisers, it is imperative to address certain concerns pertaining to their deployment. Firstly, it is important to note that organic fertilisers that have not undergone sufficient fermentation, such as manure, may contain a variety of contaminants, including germs, insect eggs and weed seeds. These can potentially lead to the emergence of pests and diseases. Therefore, it is essential to ensure that organic fertilisers have undergone adequate fermentation before application. Secondly, organic fertilisers often contain a high concentration of salt, which, if used in excess, may lead to soil salinisation and subsequent adverse effects on crop growth. It is therefore essential to regulate the dosage of organic fertiliser and to combine it with other fertilisers in a reasonable manner.
