The use of manure and composts as fertilizers is probably almost as old as agriculture. Modern chemical fertilizers include one or more of the three elements that are most important in plant nutrition: nitrogen, phosphorus, and potassium.

**Introduction:**
Fertilizers are substances that are added to soil or plants to improve their fertility and promote healthy growth. They provide essential nutrients that may be lacking in the soil, enabling plants to thrive and produce higher yields. Fertilizers can be either organic or inorganic, and they play a crucial role in modern agriculture.

**Explanation:**
Fertilizers are indeed chemical substances that are used to increase the fertility of the soil. They provide essential nutrients such as nitrogen, phosphorus, and potassium, which are necessary for plant growth. These nutrients are often present in limited quantities in natural soil, and their availability can greatly affect plant health and productivity.

**Types of Fertilizers:**
1. Organic Fertilizers: These are derived from natural sources, such as animal manure, compost, and plant residues. Organic fertilizers improve soil structure, enhance microbial activity, and release nutrients slowly over time. They also help in retaining moisture in the soil.

2. Inorganic Fertilizers: Also known as synthetic or chemical fertilizers, these are manufactured through industrial processes. They are usually water-soluble and provide nutrients in readily available forms. Inorganic fertilizers can be further classified into nitrogenous, phosphatic, and potassic fertilizers, based on their nutrient composition.

**Benefits of Fertilizers:**
1. Increased Nutrient Availability: Fertilizers supply essential nutrients that may be deficient in the soil, ensuring that plants have access to a balanced diet of nutrients required for growth.

2. Enhanced Plant Growth: By providing the necessary nutrients, fertilizers promote healthy plant growth, leading to increased yields and improved crop quality.

3. Improved Soil Fertility: Fertilizers replenish soil nutrients that are depleted over time due to continuous cultivation. This helps in maintaining soil fertility and preventing nutrient deficiencies.

4. Increased Agricultural Productivity: The use of fertilizers has significantly contributed to the increase in agricultural productivity, meeting the ever-growing demand for food in the world.

5. Precision Farming: Fertilizers allow farmers to precisely manage nutrient levels in the soil, enabling them to optimize plant growth and minimize nutrient wastage.

**Conclusion:**
Fertilizers are chemical substances that are used to increase the fertility of the soil. They provide essential nutrients to plants, promoting healthy growth and high yields. Fertilizers have played a vital role in modern agriculture, improving soil fertility and agricultural productivity.

Because fertilisers are very rich in plants nutrients like nitrogen ,phosphorus, and potassium .manure also provides plants nutrients but in less amount as compared to fertiliser. a manure is not very rich in essential plant nutrients like nitrogen, phosphorus, and potassium