Water management.pptx bsc agriculture 5th sem

Bsc agriculture

1. JAIPUR NATIONAL UNIVERSITY

2. Subject : Water Management Subject Code : BSCAGDS501T22 Submitted to : Dr. Yasir Tamboli Submitted by : Lubhanshi Kanada (R42929) Semester : 5 th Year : 3rd

3. Methods of Soil Moisture Estimation

4. Introduction Soil moisture is the amount of water present in the soil pores and is one of the most important factors governing crop growth, yield, and soil health. Knowledge of soil moisture is essential for irrigation scheduling, water resource management, and crop modeling. Since direct measurement of soil water is difficult, different scientific methods have been developed to estimate it accurately. Among these methods, Electrical Resistance Blocks, Neutron Moisture Meter, and Pressure Plate Apparatus are commonly used and provide reliable data for both research and practical agricultural applications.

5. 1.Electrical Resistance Blocks Principle • Electrical resistance blocks work on the principle that the resistance of a porous material changes with its water content.
• When placed in soil, the block absorbs or loses water depending on the surrounding soil moisture.
• As soil moisture increases, resistance decreases; as soil dries, resistance increases.

Components
• Porous block (made of gypsum, fiberglass, or nylon)
• Electrodes embedded in the block
• Resistance measuring device

6. Procedure
• Blocks are buried in the soil at desired root- zone depths.
• Electrodes are connected to a resistance meter.
• Resistance values are measured and converted into soil moisture content using calibration curves.

7. Advantages
• Simple and inexpensive
• Useful for field monitoring of soil moisture
• Non-destructive method

Limitations
• Calibration needed for different soil types
• Affected by soil salinity and temperature
• Less accurate at very high or very low moisture level

8. 2.Neutron Moisture Meter Principle
• This instrument works on the principle of neutron scattering.
• A radioactive source (commonly Americium-241 mixed with Beryllium) emits fast neutrons.
• When fast neutrons collide with hydrogen atoms in soil water, they slow down and become thermal neutrons.
• A detector counts these thermal neutrons, and the number is directly related to the soil water content.

Components
• Probe containing neutron source and detector
• Shielded control unit with scaler
• Access tubes inserted into soil

9. Procedure
• An aluminum access tube is inserted into the soil up to the desired depth.
• The probe is lowered into the tube at different depths.
• Neutron counts are recorded and converted to soil moisture content using calibration.

10. Advantages
• Measures soil moisture quickly and accurately
• Can measure soil water content at different depths
• Non-destructive and suitable for repeated measurements

Limitations
• Expensive and requires skilled operation
• Use of radioactive material requires government permission and safety precautions
• Calibration required for each soil type.

11. 3. Pressure Plate Apparatus Principle
• Soil moisture retention is studied by subjecting saturated soil samples to different pressures.
• When pressure is applied, water drains out of the soil pores until equilibrium is reached.
• The water content at a given pressure corresponds to the soil’s moisture retention characteristics.

Components • Pressure chamber with airtight lid
• Ceramic pressure plates (porous plates . Gas supply (compressed air or nitrogen) with pressure regulator.

12. Procedure
• Soil samples are saturated with water and placed on ceramic plates inside the chamber.
• Different pressures (0.1 to 15 bars) are applied.
• Water drains through the ceramic plate until equilibrium is reached.
• Moisture content is determined by weighing the soil samples before and after drying.

Applications
• Used to determine field capacity (–0.33 bar) and permanent wilting point (–15 bar).
• Helps in constructing soil water retention curves.
• Important for soil and crop research, irrigation management, and hydrological studies.

13. Advantages
• Provides accurate soil-water characteristics
• Useful in research for determining plant-available water

Limitations
• Time-consuming and labor-intensive
• Requires specialized laboratory setup
• Not suitable for rapid field estimation.

14. Conclusion Soil moisture estimation is vital for efficient water management, crop productivity, and sustainable agriculture. Among the different methods:
• Electrical resistance blocks are simple and cost-effective for field use.
• Neutron moisture meters provide accurate, rapid, and non-destructive measurements but require expertise and high investment.
• Pressure plate apparatus is mainly used in laboratories to study soil-water relationships and plant-available water.

Each method has its advantages and limitations, and the choice depends on the purpose—whether for routine irrigation scheduling, research, or detailed soil-water studies. Combining these methods often provides the most comprehensive understanding of soil moisture dynamics.

15. Thank you...