Soil Fertile: What Makes a Soil Fertile?


Soil Fertile: What Makes a Soil Fertile?

As long as soil fertility is measured only by the crop yields, the awareness about the soil will remain low. Soil in this context is just a medium where plants grow and a base to apply plant nutrients. Compared to this simple approach in conventional agriculture, soil fertility has a totally different meaning in organic agriculture.

Improving and maintaining the fertility of the soil is the central focus in organic farming. For the organic farmer, feeding the crop means feeding the soil. Only a fertile soil can yield healthy crops and it is the most important resource of every farm. Therefore, it is very important for organic farmers to gain a thorough understanding on the various factors influencing soil fertility.

Characteristically, tropical soils have been known to be fragile due to the very high extreme weather conditions it faces. Such extremes include rainfall, sunshine and other weather conditions. 

This situation has led to high rate of leaching, acidity, erosion and most importantly nutrient depletion. These have made our soils to become vulnerable and so delicate (poor) that if we do not improve its fertility status, it cannot continue to support food and fibre production for our increasing population.

Therefore, soil is an important natural nutrient medium that supports crop growth and development and good root development to enable the plant complete its crop cycle. 

It provides also a habitat for soil organisms important in agriculture especially those associated in carbon, nitrogen and phosphorus cycling and oxidation/reduction processes in soil. 

Hence the fertility status of the tropical soil is essential to enhancing good crop quality and production.

In this article, you will be able to:

· Discuss the tropical soils

· Explain soil fertility.

· Why is soil Fertility Important

· How to improve and maintain soil fertility

· Factors influencing soil fertility  


 Definition of Soil Fertility

A fertile soil may be defined as that which has the power to supply the right amount of nutrients to the plants and in the right proportion. The fertility of an agricultural soil can also be defined simply as ‘its capacity to produce the crops desired’, emphasizing the idea that soil fertility ‘is an outcome of the effects of many kinds of living organisms, and chemical and physical processes acting on the inert parent materials from which soil is made’.

Soil fertility is the level or status of a given soil with respect to its ability to supply the needed nutrients for plant growth. 

In effect, it is the nutrient supplying power of the soil.

It is also defined as the quality of nutrients which enables or helps a given soil to make provision of the right nutrients in the right quantity and in the right proportion for growth of a specific plant or crop when all necessary environmental factors such as temperature, water, and pH, light are adequate / favorable.

Soil fertility is the result of the interactions between the biological, chemical and physical properties of soil due to soil type and land use, and the effects of climate.

It is related to the potential for the sustainable production of crops and animals and can be assessed and/or described in various ways.

Soil fertility can be viewed as an ecosystem concept integrating the diverse soil functions, including nutrient supply, which promote plant production. 

Many soil properties interact to impact on crop growth, with both trade-offs and compensating effects.

Importantly, economics plays a critical role as farmers will only strive to maintain soil fertility through appropriate practices if it pays the farmer, preferably in the short term. 

Concerns about soil degradation have highlighted the need to include a much wider range of potential functions of soil alongside plant production within any definition of soil quality and soil fertility is now considered as one aspect of the broader concept of soil quality.


What is Soil Fertility?

Soil fertility is the ability of a soil to sustain plant growth by providing essential plant nutrients and favorable chemical, physical, and biological characteristics as a habitat for plant growth. Plant nutrients include the macronutrients nitrogen, phosphorus and potassium, sulfur, calcium and magnesium. Micronutrients are essentially boron, chlorine, copper, iron, manganese, molybdenum and zinc. 

Fertilizers are chemical or natural substance or material that is used to provide nutrients to plants, usually via application to the soil, but also to foliage or through water in rice systems, fertigation or hydroponics or aquaculture operations. 

Nutrient sources include chemical and mineral fertilizers, organic fertilizers, such as livestock manures and composts, and sources of recycled nutrients.


Why is soil Fertility Important?

The impacts of soil fertility are reflected in most of the Sustainable Development Goals, as they contain economic, social and environmental aspects.

The main function provided by a fertile soil is the provision of food, which is very important considering FAO’s Zero hunger objective.

·  A fertile soil also provides essential nutrients for plant growth, to produce healthy food with all the necessary nutrients needed for human health.

·  Moreover, fertility has an impact on activities with an economic impact and is therefore related to economic growth and the fight against poverty.

·  Finally, good management of soil fertility can help reduce soil, water and air pollution, regulate water resources availability, support a diverse and active biotic community, increase vegetation cover and allows for carbon neutral footprint.


How to improve and maintain soil fertility

Soil fertility is crucial for agricultural productivity and therefore for food security. It can be maintained or increased through several management practices.

·  Farmers can improve soil fertility and soil health by optimizing soil nutrient management in terms of maximizing net returns, minimizing the soil nutrients depletion, and minimizing nutrient losses or negative impacts on the environment. 

·  Governments should promote sustainable agricultural practices, technologies and management in order to improve soil fertility and nutrient management as a whole, such as Integrated Soil Fertility Management (ISFM) and Sustainable Soil Management (SSM).

·  The International Code of Conduct for the Sustainable Use and Management of Fertilizers promotes practices including nutrient recycling, and agronomic and land management to improve soil health; it recommends regulation related to the sale, distribution and labeling of fertilizer products, wherever appropriate.

· It also promotes capacity development and education programmes for all stakeholders involved in the fertilizer value chain, and encourages developed countries to assist others in developing infrastructures and capacity to manage fertilizers throughout their life cycle.

Farmers can also improve the fertility of their soil by various management practices. It is important to achieve:  

·  Protection of the soil from strong sunlight and heavy rain by means of plant cover: e.g. mulching with plant residues, green manure crops or cover crops, in order to prevent soil erosion and to preserve moisture.  

·   A balanced crop rotation or mixed cropping: a suitable sequence of annual crops grown on a field for preventing a depletion of the soil.

·   An appropriate tillage method: suitable for getting a good soil structure without causing erosion and compaction.

·   A good nutrient management: application of manures and fertilizers according to the demands of the crops in their respective growth stages.

·   Balanced feeding and protection of soil organisms: enhancing the activity of beneficial soil microbes and organisms like earth worms by supplying organic material.


How to Achieve a Fertile Soil?

What has an influence on Soil Fertility? Farmers know that the fertility of the soil depends on many factors. For the plants to grow they need to get from the soil suitable conditions for root growth, appropriate supply of water and nutrients available for uptake by roots. 

If certain soil conditions are not suitable, plant growth can be inhibited. For example water logging, acidity, compaction or shortage of nutrients can tremendously decrease the yields of some crops.


Factors influencing soil fertility  

·  Soil depth: the exploitable volume for plant roots.  Availability of water: moisture retention for continuous water supply.  

·  Drainage: most crops can’t bear water logging.

·  Aeration: Necessary for a healthy root growth and a high activity of soil life.  

·  ph (range of acidity): The soil should neither be too acidic nor too alkaline.  

· Mineral composition: Has an influence on the amount of nutrients released by weathering, the nutrient holding capacity and the soil structure.  

· Content of organic matter: Has an influence on the nutrients released by decomposition, the nutrient holding capacity, water retention, soil structure and soil life.  

· Activity of soil organisms: They are crucial for nutrient availability, water retention, a good soil structure, decomposition of organic material and soil health.  

· Contamination: high concentration of salt, pesticides or heavy metals can inhibit plant growth.


How to improve the soil structure?

A good soil structure is important for easy penetration of plant roots, good aeration, sufficient infiltration, active soil life and many other functions. Some soils are generally of a poor structure because of their mineral composition (e.g. high clay content). 

What is most important for improving the soil structure is to increase the content of organic matter. It sticks soil particles together and helps to support the work of soil organisms by providing food and shelter.


Activities that improve soil structure

·  Encourage the activity of soil organisms.

·  Apply organic matter as manure, compost, mulch etc.  

·  Protect the soil surface with mulch or plant cover.


Activities that harm the soil structure

·  Cultivating the soil in wet conditions can cause soil compaction.  

·  Frequent soil cultivation reduces the content of soil organic matter.  

·  Intensive mechanical cultivation like rotary tilling destroys the soil crumb

In conclusion, Tropical soils are highly diverse, with some soils having a high production potential. However, there are many areas where the soil resources suffer from serious limitations hindering agricultural production and development. 

Some soils have a very low chemical fertility, are extremely acid or contain toxic substances, but the exact extent of low-fertility soils and the extent of spare land is, despite advanced mapping techniques, still open for debate. 

From this article, you have learnt about the fertility of tropical soils.

Some of the key things leant include the following; -

- The definitions of soil fertility

- Some factors affecting fertility of tropical soils

- Key limitations of tropical soils

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