Table of Contents
- Drought: Types
- The effect of water deficit on the physio-morphological characteristics of the plants
- Crop adaptation and mitigation to drought
Drought
Drought is a natural disaster characterized by an extended period of abnormally low precipitation, resulting in water scarcity and significant impacts on various sectors, including agriculture.
A/c to Dorigation comission of India "Drought is a situation occving in an area where the annual rainfall is less than 75% of normal rainfall.
• Draught area - Region which experienced draught in more than 40% of the years.
In Simple terms, A drought is when there is not enough water in a place for a long time. This can happen because of many reasons, such as not enough rain, too much heat, or changes in the wind and ocean.
Drought is a natural phenomenon that can affect any part of the world. Some places have drought more often than others, such as deserts or tropical regions. Some places have drought only once in a while, such as the Dust Bowl in the United States in the 1930s. Some places have drought that is hard to see, such as when the soil loses moisture even though it rains sometimes.
Drought conditions can vary in severity, duration, and spatial extent, and they pose significant challenges to rainfed agriculture and watershed management.
Types
- Meteorological Drought:
- Meteorological drought occurs when there is a prolonged period of below-average precipitation in a region.
- It is characterized by a deficit in rainfall, snowfall, or other forms of precipitation compared to the long-term average for that area.
- Meteorological drought can be caused by factors such as changes in weather patterns, atmospheric conditions, or climate variability.
- Agricultural Drought:
- Agricultural drought is related to the availability of soil moisture and its impact on crop growth and yield.
- It occurs when soil moisture is insufficient to support normal plant development and agricultural activities.
- Agricultural drought can occur even if there is no significant deficit in precipitation, as factors like evapotranspiration and soil moisture deficits play a crucial role.
- Hydrological Drought:
- Hydrological drought refers to a deficiency in water supply in streams, rivers, lakes, and groundwater sources.
- It occurs when there is a prolonged period of reduced water availability, leading to decreased streamflow, lowered water levels in lakes and reservoirs, and depleted groundwater reserves.
- Hydrological drought is influenced by factors such as decreased precipitation, increased evaporation, and changes in land use and water management practices.
- Socioeconomic Drought:
- Socioeconomic drought is associated with the impacts of water scarcity on human activities, industries, and livelihoods.
- It occurs when the demand for water exceeds the available supply, affecting various sectors like agriculture, industry, domestic water use, and ecosystems.
- Socioeconomic drought can lead to economic losses, water rationing, conflicts over water resources, and social disruption.
It is important to note that these types of drought are interrelated and can often occur simultaneously. For example, a prolonged period of below-average precipitation (meteorological drought) can lead to reduced soil moisture (agricultural drought), which in turn affects water availability in rivers and groundwater (hydrological drought) and impacts various sectors of the economy (socioeconomic drought).
Understanding the different types of drought is crucial for effective drought management and preparedness. By monitoring weather patterns, soil moisture levels, and water availability, and implementing appropriate water conservation measures, it is possible to mitigate the impacts of drought on agriculture, water resources, and society.
Classifications of Drought (Extra)
On the basis of:
- Duration: This is the length of time that a drought lasts, from the beginning to the end. Drought duration can range from a few weeks to several years, depending on the climate and the rainfall patterns. Drought duration can affect the severity and the recovery of the drought. For example, a short-term drought may cause temporary stress on crops and soil moisture, while a long-term drought may cause permanent damage to ecosystems and groundwater.i
- Intensity: This is the degree of water deficiency during a drought. Drought intensity can be measured by various indicators, such as precipitation, soil moisture, streamflow, reservoir levels, groundwater levels, etc. Drought intensity can vary from mild to extreme, depending on the magnitude and the duration of the water shortage. Drought intensity can affect the type and the extent of the impacts of the drought. For example, a mild drought may reduce crop yields and increase fire risk, while an extreme drought may cause crop failure and water scarcity.
- Spatial extent: This is the geographic area that is affected by a drought. Drought spatial extent can vary from local to regional to global, depending on the scale and the location of the water shortage. For example, a local drought may affect only a small community or a specific sector, while a global drought may affect multiple countries and regions.
- Frequency: This is how often a drought occurs in a given area or time period. Drought frequency can be calculated by using historical records or statistical models to estimate the probability or return period of a drought event. Drought frequency can vary from rare to common, depending on the climate and the variability of the rainfall. Drought frequency can affect the preparedness and the adaptation of the society to cope with drought. For example, a rare drought may catch people off guard and cause more damage, while a common drought may encourage people to develop more resilient strategies.
- Impact: This is how a drought affects different sectors and aspects of human and natural systems. Drought impact can be classified into four categories: environmental, economic, social, and political. Environmental impact refers to how a drought affects ecosystems, biodiversity, wildlife, land degradation, etc. Economic impact refers to how a drought affects agriculture, industry, energy, tourism, etc. Social impact refers to how a drought affects health, education, culture, recreation, etc. Political impact refers to how a drought affects governance, policy, conflict, cooperation, etc.
The effect of water deficit on the physio-morphological characteristics of the plants
Water deficit, caused by drought or inadequate irrigation, has profound effects on the physio-morphological characteristics of plants. These effects are adaptive responses that enable plants to cope with limited water availability. Here are the key impacts of water deficit on plant physiology and morphology:
- Stomatal Closure:
- Water deficit triggers stomatal closure to reduce water loss through transpiration.
- Stomata are small openings on the leaf surface that regulate gas exchange and water vapour loss.
- Closure of stomata limits the entry of carbon dioxide (CO2) for photosynthesis, reducing plant growth and productivity.
- Reduced Photosynthesis:
- Water deficit impairs photosynthetic activity, as it restricts the availability of CO2 and affects the functioning of chloroplasts.
- Reduced photosynthesis leads to decreased production of carbohydrates, which are vital for plant growth and development.
- Decreased Leaf Expansion:
- Water-deficient conditions often result in reduced cell expansion and leaf growth.
- Leaves may become smaller, thicker, or exhibit curled or wilted morphology to minimize water loss through a smaller surface area.
- Chlorophyll Degradation:
- Water stress can accelerate chlorophyll degradation, leading to the yellowing or browning of leaves.
- Chlorophyll degradation affects the plant's ability to capture sunlight for photosynthesis, further reducing its energy production.
- Changes in Leaf Anatomy:
- Water deficit can induce structural changes in leaf anatomy to enhance water retention.
- Examples include thicker cuticles, increased epidermal hair density, and altered stomatal distribution to reduce water loss through transpiration.
- Altered Root Morphology:
- Water deficit promotes changes in root morphology to enhance water uptake.
- Roots may elongate deeper into the soil in search of water, exhibit increased branching, or develop root hairs to maximize water absorption.
- Reduced Growth and Biomass:
- Water deficit significantly affects plant growth, leading to reduced shoot and root growth.
- Decreased growth rates result in smaller plant size, lower biomass accumulation, and compromised overall productivity.
- Early Flowering and Senescence:
- Water stress can induce early flowering and senescence (premature ageing) in plants as adaptive strategies.
- Early flowering ensures reproductive success before further water limitations, while senescence reallocates resources from non-essential tissues to support essential functions.
- Accumulation of Osmoprotectants:
- Plants under water deficit conditions produce osmoprotectants such as proline, sugars, and organic acids.
- Osmoprotectants help maintain cellular osmotic balance, stabilize proteins, and protect cell membranes from damage caused by water deficit.
- Activation of Stress Response Pathways:
- Water deficit triggers the activation of various stress response pathways in plants.
- This includes the synthesis of stress-related proteins, antioxidants, and stress signalling molecules that help protect cells from oxidative damage and maintain cellular homeostasis.
Understanding the effects of water deficit on plant physiology and morphology is essential for implementing strategies to mitigate drought stress in agriculture. By adopting practices such as efficient irrigation, crop breeding for drought tolerance, and improved soil water management, it is possible to enhance plant resilience and productivity under water-deficient conditions.
Crop adaptation and mitigation to drought
Drought poses a significant challenge to crop production, but through crop adaptation and mitigation strategies, farmers can enhance the resilience of their crops to water-deficient conditions. These strategies aim to improve water-use efficiency, minimize yield losses, and maintain agricultural productivity.
Here are key approaches for crop adaptation and mitigation of drought:
- Crop Selection and Breeding:
- Selecting or developing crop varieties that are adapted to drought-prone regions is crucial.
- Drought-tolerant crop varieties possess traits such as deep root systems, efficient water use, and mechanisms to withstand water stress.
- Breeding programs focus on developing drought-tolerant cultivars through genetic selection and modification.
- Conservation Agriculture:
- Conservation agriculture practices, including minimum tillage, crop residue retention, and cover cropping, help improve soil structure, moisture retention, and organic matter content.
- These practices enhance water infiltration, reduce evaporation, and maintain soil moisture levels, mitigating the impact of drought on crops.
- Irrigation Management:
- Efficient irrigation techniques such as drip irrigation, precision irrigation, and deficit irrigation can optimize water use.
- These methods apply water directly to the root zone, reduce evaporation losses, and provide water based on crop water requirements, helping crops withstand drought conditions.
- Agronomic Practices:
- Adjusting agronomic practices can help crops better cope with drought stress.
- Modifying planting dates, adjusting crop density, and optimizing nutrient management can improve water-use efficiency and minimize the negative effects of water deficit on crop yield.
- Mulching:
- Applying organic or synthetic mulch to the soil surface conserves soil moisture by reducing evaporation and improving water infiltration.
- Mulching also helps control weed growth, prevent soil erosion, and maintain a more favourable soil moisture balance for crops.
- Supplemental Irrigation:
- Providing supplemental irrigation during critical growth stages or when the water deficit becomes severe can support crop development and yield.
- Targeted irrigation at specific growth stages such as flowering, pollination, and grain filling can help mitigate the yield losses caused by drought.
- Efficient Nutrient Management:
- Proper nutrient management is essential for crop resilience to drought.
- Balanced fertilization, based on crop nutrient requirements, promotes healthy plant growth and physiological functions, enabling crops to better withstand water stress.
- Soil Moisture Monitoring:
- Regular monitoring of soil moisture levels helps farmers make informed irrigation decisions.
- Soil moisture sensors, tensiometers, or satellite-based monitoring systems can provide real-time data, enabling farmers to adjust irrigation schedules and prevent over- or under-irrigation.
- Crop Rotation and Diversification:
- Crop rotation and diversification practices help break pest and disease cycles and enhance soil health and water-use efficiency.
- Including drought-tolerant crops or integrating drought-resistant varieties in the cropping system can improve overall resilience to water deficit.
- Conservation of Genetic Diversity:
- Conserving and utilizing genetic diversity is vital for crop adaptation to changing environmental conditions, including drought.
- Maintaining a diverse gene pool ensures the availability of genetic resources to develop new crop varieties with improved drought tolerance.
- Integrated Pest and Disease Management:
- Managing pests and diseases is crucial during drought stress to minimize additional crop losses.
- Integrated pest and disease management practices, including biological control, cultural practices, and appropriate pesticide use, help protect crop health under water-deficient conditions.
- Farmer Training and Knowledge Sharing:
- Providing training and knowledge-sharing platforms to farmers on drought adaptation strategies and best management practices is essential.
- Educating farmers about climate-smart agriculture techniques and promoting awareness of drought mitigation measures can enhance their ability to cope with water scarcity.
By implementing these crop adaptation and mitigation strategies, farmers can enhance the resilience of their crops to drought stress, reduce yield losses, and ensure sustainable agricultural production even in water-deficient conditions. Continuous research, innovation, and knowledge exchange are crucial for developing and promoting effective strategies to address the challenges posed by drought in agriculture.
📚 For comprehensive notes on other chapters of rainfed and dryland agriculture, please visit the website Agricorn - Rainfed Agriculture and Watershed Management.
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