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Crop Production and Management - Adding Manure and Fertilizers

Grade 8CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Nutrients are essential for the growth of plants. Continuous cultivation of crops in the same field makes the soil poor in nutrients like Nitrogen (NN), Phosphorus (PP), and Potassium (KK).

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Manure is an organic substance obtained from the decomposition of plant or animal wastes. It enhances the water-holding capacity of the soil and improves soil texture.

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Fertilizers are chemical substances which are rich in a particular nutrient. They are produced in factories. Examples include Urea, Ammonium sulphate, Super phosphate, Potash, and NPKNPK (Nitrogen, Phosphorus, Potassium).

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Crop Rotation is a method of replenishing the soil with nutrients by growing different crops alternately. For example, farmers grow legumes (like peas or beans) in one season and wheat in the next.

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The RhizobiumRhizobium bacteria present in the root nodules of leguminous plants help in the fixation of atmospheric Nitrogen (N2N_2) into a form that plants can absorb.

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Excessive use of fertilizers can make the soil less fertile and lead to water pollution. Manure is considered eco-friendly as it adds humus to the soil.

📐Formulae

Urea: CO(NH2)2\text{Urea: } CO(NH_2)_2

Ammonium Sulphate: (NH4)2SO4\text{Ammonium Sulphate: } (NH_4)_2SO_4

NPK Fertilizer Ratio: N:P:K\text{NPK Fertilizer Ratio: } N : P : K

Nitrogen Fixation: N2→Nitrates (absorbed by roots)\text{Nitrogen Fixation: } N_2 \rightarrow \text{Nitrates (absorbed by roots)}

💡Examples

Problem 1:

Differentiate between Fertilizers and Manure based on their preparation and nutrient content.

Solution:

Fertilizers are inorganic salts prepared in factories and are very rich in plant nutrients like N,P, and KN, P, \text{ and } K. Manure is a natural substance prepared in fields by decomposition and is relatively less rich in specific plant nutrients but adds humushumus to the soil.

Explanation:

Fertilizers are concentrated chemical sources of nutrients, while manure is a bulky organic source that improves soil health over time.

Problem 2:

A farmer observes that his soil has become less fertile after several harvests of wheat. He decides to plant peas in the next season. Why?

Solution:

Peas are leguminous plants that host RhizobiumRhizobium bacteria in their root nodules. These bacteria fix atmospheric N2N_2 into the soil, replenishing its nitrogen content naturally.

Explanation:

This practice is known as crop rotation, which maintains soil fertility without the heavy use of chemical fertilizers.