This can be caused by many factors, including natural factors such as heavy rainfall, or artificial factors such as irrigation and poor drainage. Waterlogging is a situation where the ground is saturated with water, to the point where it can’t absorb any more. This can be caused by things like heavy rain, or man-made factors such as bad irrigation or drainage.
The water table rising can restrict the normal supply of air in the soil, which then causes a decline in oxygen levels and an increase in carbon dioxide and ethylene levels.
If there isn’t enough air, crops will be adversely affected.
Waterlogging can prevent plants from growing and producing in anaerobic conditions, which can lead to the death of crops and plants. Additionally, the roots of plants may fail to respire properly due to the excess water in the soil, making the plants weak and more susceptible to dying or falling.
Waterlogging is a problem even when there is no excess water on the surface.
There is no one level of soil oxygen that can identify waterlogged conditions for all plants because each plant is different. Also, a plant’s root zone oxygen demand varies depending on the plant’s stage of growth.
The text is saying that in 2001, a lot of land in India was suffering from waterlogging issues. The waterlogging problems affected 4% of all the land that was being used for irrigation in the country. This is a big deal because India is a very large country.
1.4 million hectares of the 2.04 million affected by waterlogging suffered from surface water stagnation while 0.64 million hectares had a general rise in the water table. This means that sometimes the problem is natural, and at times it is man-made. About 10% of the world’s irrigated lands suffer from waterlogging.
Different Types of Waterlogging
- Riverine Flood Waterlogging
It is a type of waterlogging which occurs during the rainy seasons when floods come to nearby lands from the river. The water is waterlogged in the land and leads to the death of a number of plants or crops.
- Oceanic Flood Waterlogging
This type of waterlogging is caused by ocean waters spreading onto nearby land.
Extremes in weather can have an affect on the oceans, such as during hurricanes and tsunamis.
- Seasonal Waterlogging
During the rainy seasons, runoff water might accumulate into the lowlands and depressions, leading to waterlogging.
- Perennial Waterlogging
Perennial waterlogging can happen when deep water or swamps get rainwater and the runoff and seepage water spreads onto nearby lands.
- Sub-soil Waterlogging
This is a different type of waterlogging, which happens when the water table rises too high, especially during rainy seasons, and causes flooding.
Causes of Waterlogging
The physical features of a place can affect how well water drains from the surface. For example, a place’s elevation, the slope of its land, and the shape and arrangement of its features can all influence how quickly water runs off the surface and how long it takes the soil to absorb the water.
Waterlogging is more common in low-lying areas like valleys, depressions, and flat lowlands because surface water flows concentrate there, resulting in natural swamps and other waterlogged lands.
In areas where water cannot easily flow due to gravity, it will build up over time.
- Weather, Especially Atmospheric Conditions That Result in Heavy Rainfall and Flooding
The weather is a natural cause of waterlogging, which means that areas that experience constant or prolonged rainfall will tend to become waterlogged, either temporarily or permanently. Heavy and consistent rains raise the water table, resulting in waterlogging.
- Soil Type
Heavy clay soils, like black cotton soils, and soils that are prone to surface sealing, tend to hold moisture for long periods, which means they become waterlogged easily.
A layer that does not allow water to pass through it, located below the topsoil, can cause a false water table or perched water table. Areas with shallow soils, a hardpan close to the surface, and those with high water tables are also likely to become waterlogged, especially if they are subjected to heavy rainfall.
- Seepage Inflows
Waterlogging occurs when water from nearby sources seeps into the ground, causing the soil to become saturated. This can happen when water from lakes, rivers, or aquifers flows into lower-lying areas, or when rainwater does not drain properly.
- Excessive Irrigation and Poor Drainage System by Farmers
Waterlogging occurs when there is too much water in the soil, which can be caused by irrigation if it is not well planned. If there is poor drainage, the problem could worsen.
If there is too much irrigation, poor drainage, bad irrigation management, obstruction of natural drainage, or leakage from canals, irrigation can cause waterlogging. This is especially a problem if the area being irrigated is landlocked without any way for the water to drain away.
Effects of Waterlogging
- Poor Soil Aeration
When there is too much water in the ground, the air is forced out of the soil and into the atmosphere, and is replaced by more water.
If a plant doesn’t have enough oxygen, it will stop growing, because the carbon dioxide that builds up will prevent the plant’s roots from growing.
A lack of aeration also makes it easy for toxins and other harmful substances to grow. This also reduces the amount of microorganisms, which is essential for plants to get the nutrients they need.
- It Alters the pH of the Soil
In flooded soils, the pH changes and becomes more acidic, decreasing the soil’s alkalinity and making the growth of plants more difficult. The increasingly acidic soil cannot support plant life.
- Change in Soil Temperatures
. Waterlogging lowers the temperature of the soil, which in turn affects the microorganisms and lowers the rate of nitrogen-fixation.
- Affecting Soil Nutrients
Nitrogen is important for the soil, and waterlogged soils can suffer from a lack of nitrogen. The climate created by waterlogging can affect not only nitrogen levels but also other minerals such as sulfur, zinc, iron, manganese, phosphorus, and potassium.
Some minerals are available in such high concentrations that they become toxic to plants, while others are not available in concentrations high enough to support plant life.
- Retard Cultivation
The underlying conditions in waterlogged soils make it difficult to cultivate any crops, as they all fail to survive. However, rice is able to thrive in these conditions.
- Accumulation of Harmful Salts
Waterlogging creates an atmosphere that is rich in toxic salts which are brought to the crop’s root zone. The accumulating salts also turn the soil more alkaline and hinder the growth of crops.
- The Growth of Water-loving Wild Plants
Waterlogging creates an environment in which wild plants that love water can grow. These weeds end up killing crops that people want to grow, which creates more work to get rid of them, especially in areas where waterlogging is a big problem.
- The Loss of Cash Crops
If farmers’ crops cannot grow in waterlogged soil, they lose the opportunity to make money from selling them. This forces them to switch to rice, which may be able to grow under those conditions.
- Effects on Human Health
The presence of waterlogging creates an environment that is conducive to the breeding of disease vectors like mosquitoes, slugs, and snails. These vectors spread illnesses like malaria, bilharzia, typhoid, and others, which impact the human population, animals, and plants, and as a result, have a negative effect on the environment.
What is the Best Practice?
. It is important to install and maintain surface drainage properly, especially where sediments and nutrients may enter waterways and threaten water quality, in order to minimize negative impacts.
- Remove excess water (drainage options)
- Surface drainage – start with the perimeter
- Subsurface drainage
- Raised beds (cropping areas) – to reduce soil compaction and improve soil structure
- Minimise compaction (non-drainage options)
- Controlled traffic flat beds (cropping areas) – to reduce soil compaction and improve soil structure
- Stock management – graze and spell (rotation) based on the understanding of plant and soil needs
- Land class fencing
- Improve water storage in profile
How Can You Achieve This?
- Removal of excess water through drainage options
- Surface and sub-surface drainage is commonly used to rehabilitate waterlogged land and improve soil structure
- Currently, over 80% of dairyland has some form of surface drainage and up to 20% has sub-surface drainage (MacEwan 1998)
Questions to ask yourself when planning farm drainage:
- What is causing the waterlogging problem?
- Does this happen each year or is it only a problem in very wet years?
- Is there a sufficient outlet available?
- What are the likely benefits of draining this area?
- Which areas should be drained first?
- What type of drainage system is required? (Surface drains? Subsurface drains?)
- What are the non-drainage options?
- Review the Water Act (1989)
Surface drainage is the process of removing excess water from land in a controlled manner and as quickly as possible, to an artificial drainage system or a natural watercourse, without damaging the environment.
Types of surface drainage include:
Ditches or open drains
- These vary in size and length and can be formed by spinner cuts or excavators
- Must be very wary of constructing open drains in dispersive soil as they are highly prone to erosion
- These are usually shallow, varying in width from narrow to meters wide, but are constructed such that they are often grazed as part of the paddock
- They are sometimes used to bring drain outflows down slopes to prevent erosion without considerable expense
Humps and hollows (bedding)
- Hump and hollowing is the practice of forming (usually while renovating pastures) the ground surface into parallel convex (humps) surfaces separated by hollows. The humped shape sheds excess moisture relatively quickly while the hollows act as shallow surface drains
- Humps and hollows are useful in areas or on soil types that are not suitable for tile or mole drainage
Drainage below the surface of the soil – In addition to dealing with surface drainage, you may need to improve drainage through the soil. Subsurface drainage removes only excess water from the soil. Therefore, you need to know the type of soil before any work begins.
Types of Subsurface drainage include:
- Mole drains are unlined channels formed in clay subsoil by pulling a ripper blade (or leg) with a cylindrical foot (or torpedo) attached to the bottom through the subsoil. A plug (or expander) is often used to help compact the channel wall. The foot is usually chisel pointed
- Mole drains are used in heavy soils where a clay subsoil near moling depth (400 to 600 cm) prevents downward movement of groundwater. Mole drains do not drain groundwater but remove water as it enters from the ground surface
Gravel mole ploughs
- Gravel mole ploughs incorporate a hopper to allow finely graded gravel to fall into the mole channel. These ploughs have been used successfully in the UK in heavy soils that cannot hold “normal” mole drains
- Experimental results from northeast Victoria and Gippsland show they have promised on unstable clay soils but are expensive because of the amount of gravel and close spacing needed. Unfortunately, very few of these machines exist in southern Australia
Raised bed cropping
- Over the past decade, extensive research efforts have been directed toward the factors that contribute to waterlogging and soil structure decline under broadacre cropping regimes. The biggest development has been with raised bed techniques, which currently cover about 10% of the annual crop area in the Corangamite region
- Raised beds aim to reduce machinery compaction by using controlled traffic and to reduce waterlogging by lifting the soil above the saturated zone. Where used, raised beds have significantly improved soil structure and reduced waterlogging on cropping land, while significantly increasing agricultural productivity in high rainfall areas
The Water Act
- The Water Act (1989) provides guidance for the management of waterways and swamps. Before considering draining a wet area you should contact your local Catchment Management Authority for advice, as a permit may be required
- Minimise compaction – non-drainage options
- to reduce soil compaction and improve soil structure
- Change land use (dedicate as hay or silage paddock and graze only in summer, or remove from the grazing rotation)
- Remove stock as soon as pugging is imminent
- Allocate short grazing periods on restricted areas to allow optimal feed intake prior to the onset of pasture damage – use ‘on-off’ grazing techniques:
- This refers to removing cows from the pasture after a short period of grazing
- It has been identified as an effective method of reducing hoof compaction on broadacre grazing land as it maintains good ground cover and higher organic carbon levels
- This practice is currently being adopted in over 30% of broadacre grazing land in the Corangamite region
- Designate a “sacrifice area” to which cows are moved in any wet weather
- Construct or designate a “loafing area” (pad, laneway, barn, or woodlot) to which stock can be moved in wet conditions
- Construct a feed pad for all supplementary feeding in wet weather
Land Class Fencing
- Fence paddocks based on land capability and soil type
- It is easier to keep stock off wet areas if the paddock fences are located so that they separate the drier locations and soils from the wetter flat locations
- Consider land class fencing as a component of Whole Farm Planning
- Improve water storage in profile
Increasing the water holding capacity of the soil will decrease the likelihood of waterlogging. The topsoil structure is improved by:
- increasing soil organic matter levels
- reducing tillage
- increase the amount of surface cover to reduce the amount of surface sealing on the soil – this also assists in the reduction of water loss through evaporation
- use of raised beds
- adding gypsum