The conventional method of irrigation, flood irrigation, is generally highly inefficient when flow rates are too slow to complete the irrigation quickly (a couple of hours). This inefficiency is due to deep drainage below the root zone.
With flood irrigation, soil toward the upstream end tends to experience deep percolation, or excess water, and soil downstream may not receive enough water. This problem is exacerbated in soil with a high infiltration rate, like coarse-textured soils, because the soil absorbs water more quickly (Yonts et al., 2007).
Flood irrigation may not be the best choice because the crops could die out due to receiving too much water. The crops would harvest less crops as a result.
Unfortunately, flood or surface irrigation is the least efficient method. It's because it delivers more water than the plants need. Much of the water is lost as it evaporates into the atmosphere, while that which is excess to the plants' requirements percolates down to groundwater.
“Flood irrigation doesn't waste water,” Bali said. “The fact is it could be as efficient as other pressurized irrigation systems—and friendly to the environment.”
Furrow or flood irrigation is widely used in many parts of the world, including the US, but is the least efficient, losing about 50 percent of water applied.
Flood irrigation is less wasteful in terms of evaporation than some other methods. It is also the most energy-efficient method of irrigation. Also, of course, certain crops, like rice, thrive on it.
Excessive irrigation may cause dissolved nutrients to move through the soil and pass the root zone where they are no longer available for plant. If water with soluble fertilizers is leached and moves beyond the plant's root zone, it is likely to end up in a groundwater or surface water source.
Center Pivot Irrigation: Center pivot irrigation systems are large, mobile sprinklers that rotate around a pivot on a field. The sprinklers allow for a more efficient and uniform water and nutrient application compared to traditional flood irrigation.
Excessive irrigation can affect water quality by causing erosion, transporting nutrients, pesticides, and heavy metals, or decreasing the amount of water that flows naturally in streams and rivers. It can also cause a buildup of selenium, a toxic metal that can harm waterfowl reproduction.
Stay out of floodwater to prevent injury and infection from hidden hazards and contamination. Floodwater could contain a variety of hazards that pose a health and safety risk, including sharp objects, sewage, bacteria, chemicals, diseased insects, and animals.
Surface or flood irrigation is the least efficient manner of irrigation. When a field is flooded, more water than is needed by the plant is applied to the field and water evaporates, seeps into the ground and percolates down to the groundwater, where it can be out of reach of the plant's roots.
Flood irrigation wastes upwards of 50% of the water used. But, flood irrigation does come with benefits. Evaporation is reduced and it is the most economical and energy-efficient way to irrigate crops.
Flood irrigation flushes soils of dissolved salts that plants do not absorb. If not removed, high soil salinity can be detrimental to plant growth and yield as well as their ability to absorb moisture.
Capture and reuse of runoff: A large amount of flood-irrigation water is wasted because it runs off the edges and back of the fields.
Today, farmers in India and other developing parts of the world mainly grow crops using flood irrigation, an ancient, low-tech method that involves flooding fields with redirected river or groundwater. While this method is inexpensive, farmers have little control over when and how much to water their crops.
Drip irrigation is quickly gaining popularity as a low-cost and water-saving technique. At its core, it is a network of perforated tubes linked to a water source. The water flows through the tubes and trickles out of the perforations onto the soil.
Furrow irrigation, commonly used for crops planted in rows, such as corn, cotton, and tomatoes. Flood (border) irrigation, used for crops such as alfalfa and pasture, in which parallel strips of land are flooded.
Small tubing often becomes clogged from hard water and although new designs include filters and self-flushing emitters, they are costly. The tubing/system is unsightly. And because it's unsightly, tubing is often covered by mulch or plant foliage, making it difficult to monitor the effectiveness of the system.
Globally, 70 percent of freshwater withdrawals are used for agriculture.
Excessive irrigation can lead to waterlogging and salinization of soil, making it less fertile over time. Furthermore, irrigation water runoff can carry sediment, nutrients, and agrochemicals into rivers and lakes, causing water pollution and ecological imbalances.
Conclusion: Therefore, excessive irrigation is harmful to crops because it leads to water logging, prevents proper aeration, and ultimately suffocates the plants, hindering their growth and productivity.