In organic farming systems, soil fertility implies things beyond giving plants macro and micronutrients. The fertility of soil majorly depends on plants, soil organic matter and soil biology. Organic farming enhances soil fertility by improving its physical, biological and chemical properties. This method of farming mainly aims at maintaining nutrients in their natural reservoirs and in bioavailable forms that can be easily taken up by plants thus making the addition of chemical fertilizers needless.

Soil Organic Matter

Soil is the central component of organic farming system and organic matter is central to efficient soil fertility management. Soil organic matter contains most of the reserves of Nitrogen, Phosphorus and Sulfur. Organic farming majorly depends on the mineralization of nutrients from organic residues or soil and solubilisation of insoluble fertilizer sources. This whole process occurs with the help of soil organisms such as bacteria, fungi, nematodes and the entire range of soil flora and fauna. Organic management of soil fertility results in an increase in the soil nutrient reserves sustained release of nutrients from the soil as per plant requirements and changes in the soil physical attributes.

Managing Soil Biology

Soil microorganisms help maintain the fertility of the soil through a process called nutrient cycling. The most important source of nutrients to the crops is previous crop residues that are rich in nitrogen, phosphorus, sulfur and potassium. These crop residues are acted upon by the soil microbes which break them down to the forms that can be utilized by the crops. The crop residues were also known to contain lignin and polyphenol which are responsible for the decomposition and mineralization rates. In addition to crop residues, animal manures are the most common source of nutrients to the crop.
As mentioned, various soil organisms ranging from bacteria to earthworms play a key role in cycling the nutrients present in the soil and supply them to the plant. Besides, they help in maintaining soil structure and keep pests and diseases at bay. Hence, it is essential to improve the biological activity of the soil by maintaining good soil structure which provides better living conditions to these organisms and provide fresh organic matter for these organisms to act upon. Care should be taken not to apply any antagonistic materials that hinder biological activity.

Soil Fertility Management Practices

The availability of nutrients in the soil and their cycling is determined by the following soil fertility management practices:

1. Employing organic residues as soil amendments or sparingly soluble minerals
2. Biological nitrogen fixation as the main nitrogen source
3. Crop rotation including a mixture of fertility-enhancing leguminous crops and cash crops
4. Planting diverse crop species to fulfill various functions

The process of converting atmospheric nitrogen by the soil microbes to ammonia which can be readily assimilated by the plants is known as biological nitrogen fixation. It is important to carefully plan and manage crop rotations taking into consideration nitrogen supply from legumes. Striking a perfect balance between fertility building and fertility depleting phases of rotation ensures that sufficient nitrogen is available in the rotation. Leaching of nitrogen can be restricted by the cover and catch crops. Soil phosphorus is made available to the plant by the action of soil microbes as well as chemical transformations.

Online Course in Agribusiness at James Lind Institute

To learn more about soil fertility in the organic farming system, enroll yourself in an online training program in Agribusiness being launched at James Lind Institute. This course acquaints you with various other aspects of organic farming including crop agronomy, the role of animal health and nutrition in organic farming and environmental impacts along with a broad overview of sustainable agriculture and food security in African countries. The globally accredited and industry-specific training fine-tunes your skills to match the needs of the ever-growing market. James Lind Institute has launched online training programs in agribusiness. For more details, please visit www.jliedu.com