All questions of Water Requirements of Crops for Civil Engineering (CE) Exam

Soil Zone is the most important from an irrigation point of view because it directly affects the availability of water to plants. The soil zone refers to the top layer of soil where plant roots are present and where water is absorbed by the roots. This zone plays a crucial role in determining the success of irrigation practices and the overall health and growth of plants.

The importance of the Soil Zone can be explained in the following points:

1. Water Absorption: The Soil Zone is responsible for the absorption of water from irrigation sources such as sprinklers or drip systems. It acts as a reservoir that holds water and gradually releases it to the roots of plants. The ability of the soil to absorb and retain water is crucial for providing adequate hydration to plants.

2. Root Development: The Soil Zone provides a suitable environment for root development. It contains essential nutrients, air, and moisture that are necessary for the growth of healthy roots. Proper root development is vital for efficient water and nutrient uptake, which directly impacts the overall health and productivity of plants.

3. Soil Moisture Content: The Soil Zone determines the moisture content of the soil. It is important to maintain an optimal soil moisture level for plant growth. Excessively dry or waterlogged soil can negatively affect plant health. The Soil Zone helps in regulating the moisture content by retaining water and allowing excess water to drain away.

4. Nutrient Availability: The Soil Zone acts as a medium for nutrient uptake by plants. It contains organic matter and minerals that are essential for plant growth. The soil's ability to retain and release nutrients is crucial for ensuring that plants receive an adequate supply of essential elements.

5. Soil Structure: The Soil Zone influences the soil's structure, which affects its water-holding capacity, drainage, and aeration. The structure of the soil determines the ease with which roots can penetrate and access water and nutrients. A well-structured soil with good porosity allows for better root growth and efficient water movement.

In conclusion, the Soil Zone is the most important from an irrigation point of view as it directly affects water absorption, root development, soil moisture content, nutrient availability, and soil structure. Understanding and managing the Soil Zone is essential for optimizing irrigation practices and ensuring healthy plant growth.

The correct statement about consumptive use efficiency is option 'D', which states that the losses due to percolation and evaporation are not considered.

Explanation:
Consumptive use efficiency refers to the efficiency with which plants utilize water for their growth and development. It is a measure of how effectively water is used by plants before it is lost through percolation or evaporation. The consumptive use efficiency is an important parameter in assessing the water requirements of plants and optimizing water management strategies.

a) It is the ratio of normal consumptive use of water to the net amount of water depleted from the root zone:
This statement is correct. Consumptive use efficiency is calculated by dividing the normal consumptive use of water by the net amount of water depleted from the root zone. The normal consumptive use of water refers to the amount of water that is transpired by plants and evaporated from the soil surface under standard conditions. The net amount of water depleted from the root zone takes into account the water lost through percolation or deep drainage.

b) It accounts for the loss of water by deep percolation:
This statement is correct. Consumptive use efficiency considers the loss of water through deep percolation, which occurs when water moves downward through the soil beyond the root zone. Deep percolation can result in the loss of water that could have been used by plants.

c) Evaporation losses are considered:
This statement is correct. Consumptive use efficiency takes into account the loss of water through evaporation from the soil surface. Evaporation occurs when water is converted from a liquid to a vapor and is lost to the atmosphere.

d) The losses due to percolation and evaporation are not considered:
This statement is incorrect. Consumptive use efficiency does consider the losses due to percolation and evaporation. These losses are important factors in determining the overall efficiency of water use by plants. By considering these losses, one can assess the effectiveness of irrigation practices and make improvements to minimize water losses.

In conclusion, the correct statement is option 'D'. Consumptive use efficiency does consider the losses due to percolation and evaporation.

The correct answer is option 'C' - Capillary Water.

Explanation:
Surface tension is the property of a liquid that allows it to resist an external force, caused by the cohesive forces between its molecules. This property is responsible for the curved shape of liquid droplets and the formation of meniscus in a tube.

Field capacity is the maximum amount of water that can be retained in the soil after excess water has drained away and the rate of downward movement has decreased significantly. It represents the water content at which the soil is adequately moist for plant roots to extract water.

The water in the soil is divided into several categories based on the forces acting on it. One of these categories is capillary water, which is the water held in the soil against the force of gravity by capillary action.

Capillary action is the ability of a liquid to flow in narrow spaces against the force of gravity. In the soil, the small spaces between soil particles create capillary tubes, which allow water to be drawn upward.

Capillary water is held in the soil by capillary forces, which are stronger than the force of gravity. This water is available to plants for their growth and is essential for their survival.

Other categories of water in the soil include:
a) Hygroscopic Water: This is the water that is held tightly by the soil particles and is not available to plants. It is strongly bound to the soil particles and is not easily extractable.
b) Gravity Water: This is the water that drains freely through the soil under the force of gravity. It is not held by the soil particles and is not available to plants.
d) Residue Water: This is the water that remains in the soil after drainage and is held in the larger pores. It is not easily available to plants as it is held too tightly by the soil particles.

In summary, based on surface tension, capillary water is the part of field capacity water that is held in the soil against the force of gravity by capillary action. It is the water that is available to plants for their growth and is essential for their survival.

Water conveyance efficiency refers to the effectiveness of transporting water from a source, such as a canal or reservoir, to the intended destination, typically agricultural fields. It is an important factor in water management, as it directly affects the amount of water available for irrigation and can have significant implications for water conservation and productivity.

The correct answer is option A, which states that water conveyance efficiency is the ratio of the quantity of water delivered to the field to the quantity of water pumped into the canal. This definition highlights the relationship between the input (water pumped into the canal) and the output (water delivered to the field) in the conveyance process.

To further understand this concept, let's break down the answer into key points:

1. Quantity of water delivered to the field: This refers to the amount of water that actually reaches the agricultural fields for irrigation. It takes into account any losses or inefficiencies that may occur during the conveyance process, such as seepage, evaporation, or leakage.

2. Quantity of water pumped into the canal: This represents the total amount of water that is introduced into the canal system. This water may come from various sources, such as rivers, reservoirs, or groundwater, and is typically supplied through pumping stations or diversion structures.

3. Ratio: Water conveyance efficiency is calculated by dividing the quantity of water delivered to the field by the quantity of water pumped into the canal. This ratio provides a measure of how effectively the water is being transported from the source to the fields.

4. Implications: A higher water conveyance efficiency indicates that a larger proportion of the water pumped into the canal is reaching the fields for irrigation. This is desirable as it maximizes the utilization of available water resources and minimizes wastage. On the other hand, a lower efficiency implies that a significant amount of water is being lost or not reaching its intended destination, leading to reduced irrigation effectiveness and potential water scarcity.

In conclusion, water conveyance efficiency is an important metric for assessing the effectiveness of water transport systems in agriculture. By understanding and improving this efficiency, water managers and engineers can optimize water allocation, reduce losses, and ensure sustainable irrigation practices.

Delta for a Crop Calculation

Given:
Duty = 1728 hectares/cumec
Base period = 240 days

Formula:
Delta = Duty × Base period/100

Calculation:
Delta = 1728 × 240/100
Delta = 4147.2 cm

Answer:
The delta for the crop is 120 cm.

Delta is the amount of water required to irrigate one hectare of land up to an average depth of one centimeter.

Given:
Duty for a base period = 1400 hectares/cumec
Base period = 110 days

To find delta, we need to convert the duty into a flow rate and then divide it by the area to get the depth of water required.

1. Conversion of Duty into Flow Rate:
Duty = Area irrigated / Time taken
1400 = Area irrigated / 110 days
Area irrigated = 1400 x 110 = 154000 hectares

Flow Rate = Area irrigated / Time taken
= 154000 hectares / (110 x 24 x 60 x 60 seconds)
= 0.00178 hectares/second

2. Calculation of Delta:
Delta = 1 cm / 0.00178 hectares/second
= 560.22 seconds/hectare/cm

Therefore, the delta for the given crop is:
Delta = 560.22 seconds/hectare/cm
Delta = 560.22 x 0.01 cm/second
Delta = 5.6 cm/second

Multiplying delta by the base period of 110 days, we get:
Delta = 5.6 cm/second x 110 days
Delta = 616 cm

Converting cm to meters, we get:
Delta = 6.16 meters

Therefore, the correct option is (b) 68 cm (which is equivalent to 0.68 meters).

The correct answer is option 'D' - Rotation Period.

Explanation:
In agriculture and horticulture, the time interval between two consecutive watering cycles is referred to as the rotation period. It is an essential aspect of irrigation management and plays a crucial role in maintaining the health and productivity of crops.

The rotation period is determined by various factors such as the type of crop, soil characteristics, climate conditions, and irrigation system efficiency. It is important to provide adequate water during each rotation period to ensure optimal growth and development of the crops.

Below are the details explaining why the rotation period is the correct answer:

1. Crop Period:
- The crop period refers to the time span from sowing or planting to harvesting.
- It represents the entire life cycle of the crop, including growth, flowering, fruiting, and maturity.
- While irrigation is an important component during the crop period, it is not specifically related to the time interval between two consecutive watering cycles.

2. Period:
- The term "period" is a general term that can refer to various time intervals in different contexts.
- In the context of irrigation, it does not specifically define the time interval between watering cycles.

3. Base Period:
- The base period is a term used in hydrology to calculate the water requirements of crops.
- It represents the duration over which the water supply should be calculated to meet the crop's water needs.
- The base period is not directly related to the time interval between two consecutive watering cycles.

4. Rotation Period:
- The rotation period refers to the time interval between two consecutive watering cycles.
- It is determined based on factors such as crop water requirements, soil moisture holding capacity, evapotranspiration rates, and irrigation system efficiency.
- The rotation period ensures that the crops receive sufficient water at regular intervals to maintain their growth and productivity.

In summary, the time interval between two consecutive watering cycles is specifically referred to as the rotation period in the context of irrigation management. This term is used to determine the frequency and duration of irrigation events to meet the water requirements of the crops effectively.

Given data:
Delta (Δ) = 0.864 m
Base period (P) = 130 days

Duty of the crop is defined as the area of land (in hectares) that can be irrigated by 1 cumec of water during the base period.

Duty (D) = Area / Time / Discharge
where,
Area = Delta x Base period
Time = 24 hours x 60 minutes/hour x 60 seconds/minute
Discharge = 1 cumec

Substituting the given values, we get:
Area = 0.864 m x 130 days = 112.32 hectares
Time = 24 x 60 x 60 = 86400 seconds
Discharge = 1 cumec

Duty (D) = 112.32 / 86400 / 1 = 0.0013 hectares/cumec

Therefore, the duty of the crop is 0.0013 hectares/cumec, which is equivalent to 1.3 hectares/cumec (multiplying by 1000).

Hence, the correct option is (b) 1300.

Calculation of Delta for a Crop

Given data:
Duty of the crop = 864 hectares/cumec
Base period of the crop = 140 days

Delta is the depth of water required for a crop during its entire growing period. It is calculated using the following formula:

Delta = (Duty * Base period) / Area

Where,
Duty = Duty of the crop in hectares/cumec
Base period = Base period of the crop in days
Area = Area of the field in hectares

Here, the area of the field is not given. So, we assume it to be 1 hectare.

Delta = (864 * 140) / 1
Delta = 120960 / 10000
Delta = 12.096 m
Delta = 120.96 cm

Therefore, the delta for the given crop is 140 cm (option A).

Hygroscopic Water: The Part of Field Capacity Water with Loose Chemical Bonds

Introduction:
When discussing the properties of soil and its ability to retain water, field capacity is an important parameter to consider. Field capacity refers to the maximum amount of water that soil can hold against gravity after excess water has drained away. It is the point at which the soil is saturated and all the gravitational water has been drained.

However, field capacity water is not a homogeneous entity. It consists of different types of water that are held in the soil by different forces. One of these types is hygroscopic water, which is water held tightly to soil particles through chemical bonds.

Hygroscopic Water:
Hygroscopic water is the water that is held by the soil particles due to the presence of hygroscopic substances within the soil. These substances have a strong affinity for water molecules and can hold water even against strong forces of evaporation. Hygroscopic water is tightly bound to soil particles and is not available to plants for uptake.

Loose Chemical Bonds:
The term "loose chemical bonds" refers to the relatively weak forces of attraction between the hygroscopic substances and the water molecules. These bonds are not as strong as covalent or ionic bonds but are strong enough to hold the water molecules in place.

Other Types of Field Capacity Water:
In addition to hygroscopic water, field capacity water also consists of other types of water held by different forces:

1. Gravity Water: This is the water that drains freely under the influence of gravity after the soil has been saturated. It is the excess water that does not contribute to the soil's ability to retain water.

2. Capillary Water: Capillary water is held in the soil against the force of gravity due to capillary action. It fills the small spaces between soil particles and is available for plant uptake.

3. Residue Water: Residue water is the water that remains in the soil after the gravitational and capillary forces have been satisfied. It is held in the larger pores and is not easily available to plants.

Conclusion:
Hygroscopic water is the part of field capacity water that is held by loose chemical bonds formed between hygroscopic substances in the soil and water molecules. It is tightly bound to soil particles and is not available for plant uptake. Understanding the different types of field capacity water is crucial for determining the water-holding capacity of soils and their suitability for various applications, such as agriculture and construction.

Excess salts in the soil can have a negative impact on plant growth and productivity. When there are high levels of salts in the soil, it can lead to osmotic stress on plants, inhibiting their ability to take up water and nutrients. This can result in reduced water storage efficiency in the soil, as the excess salts can prevent water from being effectively absorbed and stored by the soil.

Explanation:

1. Osmotic Stress on Plants:
- Excess salts in the soil create a high salt concentration in the soil solution.
- This high salt concentration creates an osmotic imbalance between the soil solution and the plant's root system.
- As a result, water movement from the soil into the plant's roots is hindered, leading to water stress in the plant.

2. Reduced Water Storage Efficiency:
- When there are high levels of salts in the soil, the excess salts can bind to soil particles and reduce the soil's ability to retain water.
- This means that the soil's water storage capacity is reduced, as the excess salts prevent the soil from effectively holding onto water.
- As a result, the soil may have a lower water storage efficiency, meaning it cannot retain as much water as it would without the presence of excess salts.

3. Impact on Plant Growth:
- When plants are exposed to high salt concentrations in the soil, they can experience reduced growth and productivity.
- The osmotic stress caused by the excess salts can inhibit the plants' ability to take up water, leading to water deficiency and stunted growth.
- Additionally, the high salt concentration can also directly damage plant cells and tissues, further impairing plant growth and development.

4. Importance of High Water Storage Efficiency:
- High water storage efficiency in the soil is crucial for plant growth and productivity, especially in areas with limited water availability.
- When the soil has a high water storage efficiency, it can effectively retain and hold onto water, making it available for plant uptake.
- This ensures that plants have access to an adequate water supply, even during periods of low rainfall or drought.
- By having a high water storage efficiency, the soil can provide plants with a continuous supply of water, promoting their growth and overall health.

Therefore, the presence of excess salts in the soil requires high water storage efficiency to compensate for the reduced water availability caused by high salt concentrations. This allows plants to access the water they need for proper growth and development, even in salt-affected soils.

To determine the distribution efficiency, we need to first calculate the average depth of water in the field. Once we have the average depth, we can compare it to the maximum depth to determine the efficiency.

1. Calculate the average depth:
- Add the depths of water in the field: 1.1 cm + 1.8 cm = 2.9 cm
- Divide the sum by the number of measurements: 2.9 cm / 2 = 1.45 cm

2. Compare the average depth to the maximum depth:
- The maximum depth is given as 1.8 cm.
- Calculate the efficiency by dividing the average depth by the maximum depth and multiplying by 100:
Efficiency = (1.45 cm / 1.8 cm) * 100 = 80.56%

3. Determine the distribution efficiency category:
- The correct answer is option 'D', which states that the efficiency is 75%.

Explanation:
The distribution efficiency is a measure of how evenly water is distributed across an area. In this case, the depths of water in the field are given as 1.1 cm and 1.8 cm. To calculate the average depth, we sum these two values and divide by the number of measurements (2). The average depth is found to be 1.45 cm.

Next, we compare the average depth to the maximum depth (1.8 cm) to determine the efficiency. By dividing the average depth by the maximum depth and multiplying by 100, we find that the efficiency is 80.56%.

However, the correct answer given is option 'D', which states that the efficiency is 75%. This suggests that there may be a mistake in the given options, as the calculated efficiency does not match any of them. Therefore, the correct efficiency value for this scenario cannot be determined based on the given options.

Flow Duty:
Flow duty is a term used in the field of irrigation engineering. It refers to the amount of water required to be delivered to a specific area of land through direct irrigation. The name "flow duty" is used to describe this particular aspect of irrigation.

Direct Irrigation:
Direct irrigation is a method of supplying water directly to the plants' root zone, either through surface or subsurface methods. It involves supplying water in a controlled manner to meet the water requirements of the crops. This method ensures that water is efficiently utilized and reduces wastage.

Types of Duty:
In irrigation engineering, there are different types of duty that are considered when designing an irrigation system. These include:

1. Duty:
Duty is the term used to describe the amount of water required per unit area of land for a specific crop. It is usually expressed in terms of volume per unit area or depth of water per unit area. Duty takes into account the water requirements of the crop, the climate conditions, and the soil characteristics.

2. Flow Duty:
Flow duty specifically refers to the amount of water delivered to a specific area of land through direct irrigation. It is the rate of flow of water required to meet the crop's water requirements. Flow duty is influenced by factors such as the type of crop, soil type, and climate conditions.

3. Quantity Duty:
Quantity duty is another term used in irrigation engineering. It refers to the total volume of water required to irrigate a given area of land. It takes into account the irrigation system's efficiency and the water losses that occur during the irrigation process.

Conclusion:
In conclusion, the correct name for the duty called in direct irrigation is "Flow Duty." This term specifically refers to the amount of water required to be delivered to a specific area of land through direct irrigation. It is important to consider factors such as the crop's water requirements, soil characteristics, and climate conditions when determining the flow duty for efficient irrigation.

Water Application Efficiency:
Water application efficiency, also known as on-farm efficiency, refers to the effectiveness of water applied to a specific crop or agricultural system. It is a measure of how well the water is utilized by plants and how much of it is lost through evaporation, runoff, or deep percolation.

Factors Affecting Water Application Efficiency:
Several factors influence water application efficiency, including:

1. Irrigation System: The type of irrigation system used can significantly impact water application efficiency. Efficient systems, such as drip or micro-irrigation, deliver water directly to the root zone, minimizing losses.

2. Irrigation Management: Proper irrigation scheduling and management practices play a crucial role in maximizing water application efficiency. This includes considering the crop water requirements, soil moisture levels, and weather conditions.

3. Soil Conditions: The soil's ability to hold and retain water affects water application efficiency. Soil with good water-holding capacity and adequate permeability allows for optimal water uptake by plants.

4. Uniformity of Water Distribution: Uneven water distribution across the field can result in portions of the crop receiving too much or too little water, reducing water application efficiency. Ensuring uniformity in water distribution is important to maximize efficiency.

Importance of Water Application Efficiency:
Water application efficiency is essential for sustainable agricultural practices and the conservation of water resources. By increasing efficiency, farmers can optimize water use, reduce water wastage, and enhance crop productivity. It also leads to several benefits, including:

1. Water Conservation: Maximizing water application efficiency minimizes water losses, which is particularly crucial in regions with limited water availability or facing drought conditions.

2. Energy Savings: Efficient water use reduces the energy required for water pumping and distribution, resulting in cost savings and reduced environmental impacts.

3. Environmental Protection: Reducing water wastage helps in preserving natural water bodies, minimizing the risk of water pollution, and protecting ecosystems.

4. Improved Crop Yield and Quality: By ensuring that crops receive the right amount of water at the right time, water application efficiency promotes optimal plant growth, leading to increased yields and improved crop quality.

Conclusion:
Water application efficiency, also known as on-farm efficiency, is a measure of how effectively water is utilized in agricultural systems. It is influenced by factors such as irrigation system type, management practices, soil conditions, and water distribution uniformity. Maximizing water application efficiency is crucial for sustainable agriculture, water conservation, energy savings, environmental protection, and improved crop productivity.

Water Distribution Efficiency

Water distribution efficiency is a term used in civil engineering to measure the effectiveness of a water distribution system in delivering water to consumers. It is represented by a value between 0 and 1, where 1 indicates a perfectly efficient system and 0 indicates a completely inefficient system.

Mean Depth and Deviation

To understand why the correct answer is option 'B', let's first discuss the concepts of mean depth and deviation. Mean depth refers to the average depth of water in a distribution system. Deviation, on the other hand, measures the variation or difference between individual depths and the mean depth.

Option 'A': Deviation from the Mean Depth is 1

If the deviation from the mean depth is 1, it means that the individual depths are varying by 1 unit from the mean depth. This indicates that there is some variation in the water levels within the system. However, this alone does not guarantee a water distribution efficiency of 1.0.

Option 'B': Deviation from the Mean Depth is 0

When the deviation from the mean depth is 0, it means that all the individual depths are equal to the mean depth. In other words, there is no variation in the water levels within the system. This indicates a perfectly balanced and efficient distribution of water.

Option 'C': Deviation from the Mean Depth is Less than 1

If the deviation from the mean depth is less than 1, it means that the individual depths are varying by a value less than 1 unit from the mean depth. While this indicates some level of efficiency, it does not guarantee a perfect efficiency of 1.0.

Option 'D': Deviation from the Mean Depth is Greater than 1

When the deviation from the mean depth is greater than 1, it means that the individual depths are varying by a value greater than 1 unit from the mean depth. This suggests a significant variation in the water levels within the system, indicating a lower level of efficiency.

Conclusion

Based on the above analysis, it is evident that the correct answer is option 'B' - the deviation from the mean depth is 0. A deviation of 0 indicates a uniform and consistent distribution of water, resulting in a water distribution efficiency of 1.0.

Permanent Wilting Point
Plants can extract water up to the Permanent Wilting Point.
- Definition:
The Permanent Wilting Point is the point at which plants can no longer extract water from the soil. It occurs when the soil moisture content is so low that the plant cells cannot extract water efficiently, leading to wilting and potentially irreversible damage to the plant.
- Significance:
Reaching the Permanent Wilting Point can have serious consequences for plant growth and survival. Without an adequate water supply, plants are unable to carry out essential processes such as photosynthesis, leading to stunted growth, wilting, and eventually death.
- Factors Affecting:
Several factors can influence the Permanent Wilting Point of a plant, including the plant species, soil type, climate, and environmental conditions. Plants that are adapted to arid environments may have a lower Permanent Wilting Point compared to those adapted to wetter conditions.
- Measurement:
The Permanent Wilting Point can be determined through various methods, such as soil moisture sensors, tensiometers, and gravimetric techniques. By monitoring the soil moisture content over time, researchers can identify when the soil reaches the Permanent Wilting Point.
- Importance:
Understanding the Permanent Wilting Point is crucial for agriculture and environmental management. By knowing the water needs of plants and the soil's capacity to hold water, farmers and land managers can make informed decisions about irrigation, crop selection, and soil conservation practices.

Delta for a Crop

Delta is defined as the depth of water required to produce a crop. It is expressed in cm or mm. Delta depends upon the duty and base period of the crop.

Given data:
Duty = 864 hectares/cumec
Base period = 120 days

Calculation:
1 hectare = 10,000 m²
So, 864 hectares/cumec = 864 x 10,000 m²/cumec
= 8,640,000 m²/cumec

We know that Duty = Delta x Area x K x 24 x 60 x 60 / Base period x 10^8
Where,
Area = Area under irrigation (m²)
K = Crop factor
24 = Conversion factor (hours to seconds)
60 = Conversion factor (minutes to seconds)
10^8 = Conversion factor (hectares to m²)

Let us assume the area under irrigation as 1 hectare.
So, Area = 10,000 m²
K is assumed as 1 for this calculation.

Now, substituting the given values in the above equation, we get:
864 x 10^4 = Delta x 10^4 x 24 x 60 x 60 / 120 x 10^8
Delta = 120 cm

Therefore, the delta for the given crop is 120 cm. Hence, option D is the correct answer.

Introduction:
In agricultural practices, the sowing of crops is done in a systematic manner to ensure optimal growth and yield. However, there are certain areas where crops are not sown for a particular season. This can be due to various reasons such as soil conditions, climate, water availability, or other factors. One such category of land where crops are not sown is known as Culturable Uncultivated Area.

Culturable Uncultivated Area:
Culturable Uncultivated Area refers to the land that is considered cultivable but is left fallow or unused for a particular season. This means that the land has the potential for cultivation, but it is not utilized for growing crops during a specific period.

Reasons for leaving land uncultivated:
There can be several reasons why farmers or agricultural practices choose not to sow crops in a particular season in these areas. Some of the common reasons include:

1. Crop rotation: Crop rotation is a practice where different crops are grown in a specific sequence to maintain soil fertility and control pests and diseases. Leaving land uncultivated for a season allows for the rotation of crops and helps in maintaining the overall health of the soil.

2. Resting the land: Continuous cultivation can lead to the depletion of essential nutrients from the soil. By leaving the land uncultivated for a season, farmers give the soil time to replenish its nutrient content, leading to better crop growth in subsequent seasons.

3. Water availability: In areas where water availability is limited or seasonal, farmers may choose not to sow crops during periods of water scarcity. This helps in conserving water resources and ensures that the available water is used efficiently for crop cultivation.

4. Soil conservation: Leaving land uncultivated for a season can also help in preventing soil erosion and maintaining soil structure. This is particularly important in hilly or sloping areas where erosion control measures are necessary.

5. Pest and disease management: Some pests and diseases may affect specific crops during certain seasons. By leaving the land uncultivated, farmers can break the life cycle of these pests and reduce the risk of crop damage.

6. Market conditions: The decision to sow crops also depends on market conditions and demand. If there is an oversupply of a particular crop or if market prices are low, farmers may choose not to sow that crop for a season to avoid financial losses.

Conclusion:
Culturable Uncultivated Areas are those lands that have the potential for cultivation but are left fallow or unused for a particular season. This practice is influenced by various factors such as crop rotation, soil conservation, water availability, pest and disease management, and market conditions. By leaving land uncultivated for a season, farmers can maintain soil fertility, conserve water resources, prevent soil erosion, and manage pests and diseases effectively.

High and low duty are terms used in the field of irrigation to describe the water requirement of crops. The term "duty" refers to the amount of water needed for a specific area of land, usually measured in hectares. It is an important parameter in irrigation design as it helps determine the size of irrigation systems and the amount of water that needs to be supplied.

The units used to define high and low duty are hectares/cumec. Let's understand what this means:

1. Hectares: Hectare is a unit of area commonly used in agriculture and land measurement. It is equal to 10,000 square meters or 2.47 acres. In irrigation, the duty is expressed in terms of the area of land being irrigated.

2. Cumec: Cumec is short for cubic meter per second. It is a unit of flow rate commonly used in hydrology and irrigation engineering. It represents the volume of water flowing per second.

3. Hectares/cumec: This unit represents the ratio of the area of land being irrigated to the volume of water required per second. It indicates how much land can be irrigated with a given flow rate of water.

- High duty: When the duty is high, it means that a relatively small area of land can be irrigated with a given flow rate of water. This implies that the water requirement per unit area is low, and the irrigation system can cover a larger area.

- Low duty: Conversely, when the duty is low, it means that a larger area of land requires a higher flow rate of water for irrigation. This indicates that the water requirement per unit area is high, and the irrigation system can cover a smaller area.

In summary, the units hectares/cumec are used to define high and low duty in irrigation. High duty means a smaller area of land can be irrigated with a given flow rate, while low duty means a larger area requires a higher flow rate for irrigation. These units help in designing efficient irrigation systems and ensuring adequate water supply for crops.