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Crop Production and Management - Irrigation Systems and Water Management

Grade 8CBSE

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

🔑Concepts

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Irrigation is the artificial supply of water to crops at regular intervals. The time and frequency of irrigation vary depending on the type of crop, the nature of the soil, and the season. For example, the rate of evaporation of H2OH_2O is higher in summer, requiring more frequent irrigation.

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Water is essential for plants as they contain nearly 90%90\% water. Nutrients dissolved in H2OH_2O are transported to various parts of the plant, and it also protects the crop from both frost and hot air currents.

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Traditional Methods of Irrigation include the Moat (pulley-system), Chain pump, Dhekli, and Rahat (Lever system). These methods are cheaper but often lead to significant water wastage and are less efficient.

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Modern Methods of Irrigation are designed to conserve water. The Sprinkler System uses perpendicular pipes with rotating nozzles to spray water like rain, making it ideal for uneven land. The Drip System delivers H2OH_2O drop by drop directly at the position of the roots, ensuring zero wastage.

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Waterlogging occurs when excess water accumulates in the soil. This reduces the air available to the roots for respiration and can increase soil salinity, which negatively impacts crop yield.

📐Formulae

Water Content in Plants≈90%\text{Water Content in Plants} \approx 90\%

Irrigation Efficiency (\eta)=Water stored in the root zoneWater delivered to the field×100\text{Irrigation Efficiency (\eta)} = \frac{\text{Water stored in the root zone}}{\text{Water delivered to the field}} \times 100

Rate of Evaporation∝Temperature\text{Rate of Evaporation} \propto \text{Temperature}

💡Examples

Problem 1:

A farmer is cultivating fruit trees in a region where water availability is very poor. Which modern irrigation system should he adopt to ensure the highest water-use efficiency?

Solution:

The farmer should adopt the Drip Irrigation System.

Explanation:

In a drip system, H2OH_2O falls drop by drop directly at the base of the roots. This minimizes evaporation and runoff, making it the most efficient system for water-scarce regions and for perennial plants like fruit trees.

Problem 2:

Why does a crop grown in sandy soil require more frequent irrigation than a crop grown in clayey soil?

Solution:

Sandy soil has a lower water-retaining capacity compared to clayey soil.

Explanation:

Sandy soil particles are larger and have more space between them, allowing H2OH_2O to percolate downwards quickly. Therefore, the frequency of irrigation must be increased to maintain the necessary moisture levels for the plants.

Problem 3:

Explain why over-irrigation can lead to a decrease in crop yield.

Solution:

Over-irrigation leads to Waterlogging.

Explanation:

When the soil is saturated with water, the air spaces between soil particles are filled with H2OH_2O, preventing the roots from taking in O2O_2 for respiration. Additionally, it can lead to an accumulation of salts on the soil surface, which is toxic to most crops.