Class Notes:
1. Need and Classification of Irrigation
1.1 Need for Irrigation:
- Water Supply for Crops: Ensures adequate moisture for plant growth, especially during dry periods.
- Temperature Control: Helps maintain suitable temperatures for crops during hot weather.
- Soil Fertility: Assists in the absorption of nutrients from the soil.
- Weed Control: Facilitates weed control by creating conditions that discourage weed growth.
- Enhances Yield: Contributes to higher agricultural productivity and crop quality.
1.2 Classification of Irrigation:
- Surface Irrigation: Water is applied directly to the soil surface (e.g., furrow, basin, and border irrigation).
- Subsurface Irrigation: Water is applied below the soil surface (e.g., drip and trickle irrigation).
- Sprinkler Irrigation: Water is sprayed into the air and allowed to fall like rain over the crops.
- Localized Irrigation: Water is applied to a specific location, such as around the root zone of plants (e.g., drip irrigation).
2. Historical Development and Merits and Demerits of Irrigation
2.1 Historical Development:
- Ancient Times: Earliest evidence of irrigation dates back to Mesopotamia, Egypt, and the Indus Valley Civilization.
- Medieval Period: Development of canal systems and terraced fields in Asia and the Middle East.
- Modern Era: Advancements in technology led to the development of sprinkler and drip irrigation systems.
2.2 Merits of Irrigation:
- Increased Agricultural Production: Ensures consistent water supply, leading to better crop yields.
- Stabilizes Food Supply: Reduces dependency on rainfall and helps in planning agricultural activities.
- Economic Growth: Enhances the livelihood of farmers and contributes to the economy.
- Employment Opportunities: Generates jobs in rural areas through farming and irrigation-related activities.
2.3 Demerits of Irrigation:
- Waterlogging: Excessive irrigation can lead to waterlogged soils, reducing crop productivity.
- Salinization: Improper irrigation practices can cause the accumulation of salts in the soil.
- High Initial Cost: Installation and maintenance of irrigation systems can be expensive.
- Environmental Impact: Large-scale irrigation projects can lead to ecological imbalances.
3. Types of Crops and Crop Season
3.1 Types of Crops:
- Cereal Crops: Wheat, rice, maize, barley.
- Pulses: Lentils, chickpeas, beans.
- Oilseeds: Sunflower, soybean, groundnut.
- Fiber Crops: Cotton, jute.
- Vegetables and Fruits: Tomato, potato, mango, banana.
3.2 Crop Season:
- Kharif Season: Crops sown at the beginning of the monsoon (e.g., rice, maize, cotton).
- Rabi Season: Crops sown at the beginning of winter (e.g., wheat, barley, mustard).
- Zaid Season: Crops grown between Rabi and Kharif seasons (e.g., watermelon, cucumber).
4. Duty, Delta, and Base Period
4.1 Duty:
- Definition: The amount of land that can be irrigated with a unit volume of water.
- Measurement: Expressed as hectares per cubic meter (ha/m³).
4.2 Delta:
- Definition: The total depth of water required to raise a crop over a specific area.
- Measurement: Expressed in centimeters (cm).
4.3 Base Period:
- Definition: The total time period from the first irrigation to the last during the cropping season.
- Measurement: Expressed in days.
5. Consumptive Use of Crops
5.1 Definition:
- The total quantity of water used by a crop for transpiration and evaporation from the adjacent soil.
5.2 Factors Affecting Consumptive Use:
- Climate: Temperature, humidity, wind speed, and solar radiation.
- Crop Type: Different crops have varying water requirements.
- Soil Type: Soil texture and structure influence water retention and usage.
6. Estimation of Evapotranspiration
- Lysimeter Method
- Pan Evaporation Method
- Penman-Monteith Equation
- Blaney-Criddle Method
- Hargreaves-Samani Method
- Thornthwaite Method
This unit provides a comprehensive foundation in understanding the essential aspects of crop water requirements. By mastering these concepts, you'll be well-prepared to tackle the challenges of efficient water management in irrigation engineering.
GCR Link https://classroom.google.com/c/NjkxNDg1MDMxMzk4?cjc=ip3b664