Soil Fertility and Soil Productivity

Soil Fertility and Soil Productivity are the cornerstones of productive agriculture, giving rise to healthy plant growth and abundant agricultural yields. While soil productivity refers to the soil’s ability to sustain healthy crop development under particular management practices and environmental conditions, soil fertility refers to the soil’s ability to supply nutrients required for plant growth. Fertile soils that possess ideal physical qualities, balanced nutrient levels, and encourage robust plant growth are conducive to long-term agricultural productivity.

Introduction to Soil Fertility and Soil Productivity

Important ideas in agriculture are soil fertility and soil productivity, both of which are necessary for productive crop cultivation. The term “soil fertility” describes the soil’s capacity to provide plants with the necessary nutrients for growth and development. Together with micronutrients like iron, manganese, and zinc, these nutrients also comprise macronutrients like potassium, phosphorus, and nitrogen. Rich soil provides sufficient nutrients to plants, enabling them to flourish healthily.

Conversely, soil productivity refers to the soil’s ability to support plant growth and output over an extended period of time. It’s a more comprehensive measurement that takes into account not just the amount of nutrients present but also the structure, water-holding ability, and microbiological activity of the soil. Consistent and high-yield agricultural production is facilitated by productive soil, and this is necessary to meet the expanding population’s food needs. Therefore, one of the key factors affecting agricultural sustainability is soil productivity.

Manure

Manure is a term for organic elements obtained from animal excrement, crop leftovers, or decayed organic debris. It is an essential part of sustainable agriculture. It functions as a natural fertilizer, enhancing soil structure and water retention and adding vital nutrients including potassium, phosphorus, and nitrogen. Manure, as opposed to synthetic fertilizers, releases nutrients gradually, enhancing soil fertility and sustainability over the long run. Manure is a fundamental component of environmentally friendly agricultural operations since it is used by farmers all over the world to increase crop yields, preserve the health of the soil, and lessen dependency on chemical inputs.

The Importance of Organic Manures

Due to their substantial improvement in soil fertility and structure, organic manures are extremely important in agriculture. Organic manures support the soil’s long-term health, as opposed to chemical fertilizers, which offer a rapid but transient nutritional boost. In order to do this, they add vital nutrients like potassium, phosphorus, and nitrogen, which are progressively released when the organic material breaks down. By supplying nutrients gradually, this moderate release guarantees that plants develop stronger and healthier.

Increasing microbial activity in the soil is one of the main advantages of using organic manures. When organic matter is present, microorganisms like fungi, bacteria, and earthworms flourish because they can break it down and transform it into forms that plants can readily absorb. In addition to increasing nutrient availability, this biological activity improves soil structure by causing the soil to become more crumbly, which facilitates easier root penetration. Aeration and drainage, which are critical for plant health, are also improved by improved soil structure.

Water retention in the soil can be improved by using organic manures, which is another important benefit. Fertile soils require less frequent irrigation because organic matter absorbs and retains water like a sponge. Due to the fact that it conserves water while guaranteeing crops receive enough moisture, this is especially advantageous in areas with low water supplies. Being better equipped to resist heavy rains and less prone to compacting soil are two other benefits of enhanced water retention that help lower soil erosion.

Classification of Organic Manures

Green manures, plant-based manures, and animal-based manures are the three basic categories into which organic manures are generally divided in Nepalese farming. Every category has special qualities and contributes differently to crop productivity and soil health.

1. Animal-based Manures:

Goat dung, cow dung, and chicken litter are examples of manures that come from animals in this category. These manures are abundant in vital elements that are necessary for plant growth, such as potassium, phosphate, and nitrogen. For example, cow dung is a common and traditional manure used in Nepal that is valued for its capacity to improve soil structure and balance of nutrients. Conversely, poultry litter has a high nitrogen content and works especially well to increase crop yields.

2. Plant-based Manures:

Compost, agricultural leftovers, and other products originating from plants are included in this category of manure. Through the process of composting, organic materials like leaves, kitchen scraps, and agricultural waste are broken down to create a nutrient-rich soil supplement. Grass and other crop wastes are frequently spread back onto the field after harvest, where they break down and replenish the soil with nutrients. These manures are excellent for boosting microbial activity, strengthening soil fertility and structure, and retaining more water. Because plant-based manures recycle organic waste and lessen the need for synthetic fertilizers, they are especially prized for their sustainability.

3. Green Manures: 

Green manures are crops specifically grown to be plowed back into the soil to improve its fertility and organic matter content. Common green manure crops in Nepal include legumes like clover, alfalfa, and beans, which are capable of fixing atmospheric nitrogen, thereby enriching the soil. These crops are typically grown during fallow periods or as cover crops, preventing soil erosion and suppressing weeds. The incorporation of green manures into the soil enhances its structure, increases microbial activity, and contributes to long-term soil health.

Characteristics of Different Manures

Sustainable agricultural methods depend on organic manures because they enhance soil health and give crops vital nutrients. To maximize the benefits of different manures, it is essential to understand their peculiarities. The distinct nutrient profiles and characteristics of plant-based, animal-based, and green manures affect how they are applied in Nepalese agriculture.

Manures derived from animals, such cow dung and chicken litter, are high in potassium (K), phosphorus (P), and nitrogen (N). Poultry litter gives higher nutrient concentrations, with roughly 1.5% N, 1.3% P, and 0.8% K, compared to cow dung, which often includes 0.5% N, 0.2% P, and 0.5% K. Over time, the gradual breakdown of these manures releases nutrients steadily. But because of their high moisture content, they need to be managed carefully to prevent nutrient loss and odor problems. Composting or direct absorption into the soil are common application techniques that improve nutrient availability and lower infections.

Green Manure Used by Nepalese Farmers

Legume crops such as soybean, lentils, and peas, along with grasses like Sunnhemp, Dhaincha, and Sesbania, are commonly grown in Nepal using green manure. These are crops that are planted on fallow fields or that are interplanted with other crops and then integrated into the soil to increase fertility. Green manures improve soil structure, inhibit weed growth, provide more organic matter, and replenish the soil with nitrogen through biological nitrogen fixation. This benefits Nepal’s smallholder farmers who have limited access to chemical fertilizers and increases the sustainability of the country’s agricultural systems.

Fertilizers

Fertilizers are compounds or mixtures that are applied to plants or soil to increase fertility and stimulate growth. Fertilizers include vital nutrients. Nitrogen, phosphorus, potassium, and other micronutrients are among these nutrients that are essential for the growth and productivity of plants.

Classification of Fertilizers

Fertilizers are classified based on their nutrient content and composition. The main categories of fertilizers include:

1) Nitrogenous Fertilizers

• The main nutrient in nitrogenous fertilizers is nitrogen. They improve the development of leaves, the growth of plants, and total vegetative growth.
• Ammonium nitrate, calcium ammonium nitrate, ammonium sulfate, and urea are examples of common nitrogenous fertilizers.

2) Phosphatic Fertilizers

• Phosphorus is the main nutrient found in phosphorous fertilizers. For plants to produce roots, flowers, fruits, and overall, phosphorus is necessary.
• Rock phosphate, diammonium phosphate (DAP), triple superphosphate (TSP), and single superphosphate (SSP) are a few types of phosphatic fertilizers.

3) Potassic Fertilizers

• Potassium is the main nutrient in fertilizers that contain potassium. In addition to being essential for plant metabolism, potassium also regulates water and helps plants resist illness.
• Potassium sulfate, potassium nitrate, and potassium chloride (muriate of potash) are examples of common potassic fertilizers.

Biofertilizers

Natural fertilizers called biofertilizers are made of live microorganisms that enrich soil fertility and encourage plant growth by making vital nutrients more accessible to plants. Biofertilizers are sustainable and friendly to the environment, in contrast to chemical fertilizers.

Types of Biofertilizers

1) Saprophytes

Saprophytes are microscopic organisms that are essential to the breakdown of organic substances in soil. They decompose dead plant and animal remains, transforming them into less complex materials that plants can easily take up as nutrients. Important nutrients like sulfur, phosphorous, and nitrogen are added to the soil during this breakdown process. Saprophytes promote healthy plant growth and increase soil fertility by increasing nutrient availability, which helps create an agricultural environment that is both nutrient-rich and sustainable.

2) Symbiotic Bacteria

Symbiotic bacteria live in the root nodules of leguminous plants and develop mutually beneficial partnerships, such as Rhizobium. In order to greatly increase soil nitrogen levels without the use of artificial fertilizers, these bacteria fix atmospheric nitrogen into a form that plants can use. Increased soil fertility, strong plant growth, and greater yields are all facilitated by this symbiotic partnership. Restoring critical nutrients in agricultural systems is a natural and effective method.

3) Blue-Green Algae (Cyanobacteria)

Photosynthetic microorganisms that can fix atmospheric nitrogen are referred to as blue-green algae, or cyanobacteria. Both Anabaena and Nostoc are examples. Their addition to the soil enhances its structure and fertility by supplying organic matter and fixed nitrogen. When it comes to maintaining high productivity and healthy soil, blue-green algae are particularly helpful in rice paddies and other wet agricultural systems.

4) Azolla

With the nitrogen-fixing cyanobacterium Anabaena azollae, a little water fern known as Azolla has a symbiotic interaction. Azolla releases large amounts of atmospheric nitrogen into the soil when it is mixed in as green manure, thanks to this collaboration. Azolla is a chemical fertilizer that is frequently used in rice farming. It improves crop yields and soil fertility, making nitrogen more available and lowering the requirement for chemical fertilizers.

5) Azotobacter

Soil contains free-living nitrogen-fixing bacteria called azotobacter. It can fix atmospheric nitrogen without a host plant, unlike symbiotic bacteria. Additionally, azotobacter creates compounds that stimulate plant growth and development, like vitamins and phytohormones. Azotobacter enhances crop yield and soil health by fixing nitrogen on its own and promoting plant development.

6) Mycorrhiza

Mycorrhiza, which is divided into ectomycorrhiza and endomycorrhiza (arbuscular mycorrhiza), is the term used to describe the symbiotic relationship that fungus have with plant roots. These fungus help the plant absorb more water and nutrients from the soil, especially phosphorus. Plants that have mycorrhizal relationships grow healthier and more robust overall, and are better able to withstand environmental challenges like drought and poor soil.

Factors Affecting Fertilizer Use

• Climate: Leaching and nutrient availability are influenced by rainfall and temperature. Nutrients may quickly leach away in areas with high rainfall, requiring more regular treatments.
• Soil pH: Soil pH influences the availability and solubility of nutrients. For instance, soils that are extremely acidic or alkaline have less accessible phosphorus.
• Crop Type: The nutrient requirements and absorption efficiency of different crops vary. While legumes can fix atmospheric nitrogen, high-demand crops like wheat and maize require more nutrients.
• Water Availability: Plants need enough wetness to absorb nutrients. To guarantee that nutrients are available to plants when they’re most needed, fertilizer application in irrigated areas needs to be coordinated with irrigation schedules.

Time of Fertilizer Application

• Pre-planting: In order to provide the soil with vital nutrients, fertilizers are applied prior to seeding. Because they are less soluble in soil, minerals like potassium and phosphorus require special attention.
• At Sowing: To help seedlings grow more quickly in their early stages, starter fertilizers are sprayed on when they are planted.
• Split Application: During various stages of crop growth, fertilizers—particularly nitrogen—are administered in numerous dosages. This lowers the possibility of leaching or runoff and guarantees a consistent supply of nutrients.
• Top dressing: To continue supplying the crop with the nutrients it needs, more fertilizer is sprayed on during the growth season. Since nitrogen is required in significant quantities during the vegetative growth phase, this is frequently done for it.

Methods of Fertilizer Application

• Broadcasting: Applying fertilizer to the whole field surface in an uniform layer. Although this procedure is straightforward and appropriate for top dressing and pre-planting, runoff and volatilization may result in nutrient losses.
• Banding: In the vicinity of the planting lines or seed rows, fertilizer is applied in bands. This technique lowers nutrient losses while increasing the availability of nutrients to early plants.
• Side Dressing: Growing plants receive an application of fertilizer along their sides. In order to provide a steady supply of nutrients throughout the growth season, this technique is frequently utilized for nitrogen application.
• Fertigation: By applying fertilizer through the irrigation system, nutrients can be precisely delivered to the root zone. This technique is effective and guarantees that plants have easy access to nutrients.

Frequently Asked Question(FAQ)

Related Articles

• The cropping system
• Seed and Seed quality