Water as we all know is essential for life to all living organisms. This water all living things need for survival in every way possible and no living thing can live without this precious liquid in their bodies for effective daily activities. Knowing how excess water affects plant growth gives you the farmer more ideas as to how you should provide adequate water to plants.
Water acts as a solvent for a wide variety of substances which makes it suitable for housing a vast range of reactions. It participates as a reagent in many chemical processes in the cell notably, photosynthesis. Water makes plants and plant parts turgid. It aids the translocation of photosynthesis from sites to sink. Water aids the uptake of mineral nutrients from the soil or media. It cools the plants by taking away latent heat through transpiration.
Excess rainfall on plant growth
- Direct damage to shoots (breakage of branches)
- Destruction of flowers
- High incidence of pest and diseases
- It interferes with activities of pollinators
- Leads to leaching of nutrients
- Waterlogged conditions/flooding which can lead to death of roots since it reduces soil aeration and can also produce toxic compounds.
The severity of flood damage depends on; susceptibility of the plant species, the variety, the water table, the air temperature, soil texture, presence and type of microorganisms in the soil.
How to maintain soil moisture
- Improve structure/texture of the soil. It can be done by tillage and application of soil amendments (organic manure)
- Reduce evaporation of water by mulching and watering late evening
- Cultivate economic water users such as Allium (onion and shallot), asparagus and some solanaceous plants
- Use of shade nets which reduces evaporation of moisture but can also reduce photosynthesis. It is therefore applicable on small farms.
How to manage excess water for plant growth
- Use of protected cultivation e.g. use of shade nets and plastic or glass houses
- Manipulate soil texture/structure e.g. tillage
- Provide drainage canals or farrows
- Cultivate water loving plants e.g. cocoyam
Drought and drought management
Until plants develop well established root system before dry season sets in, they cannot survive unless they are irrigated or are drought tolerant. Short term drought during flowering of determinate plants can significantly reduce yield. Short term drought may not affect indeterminate plants because; they flower within a longer period of time. Roots of determinate plants absorb water from the lower soil depth.
How plants tolerate drought
Some plants avoid drought while others tolerate it. Plants that avoid drought actually do avoid the drying of their tissues by maintaining their uptake and or by reducing water loss. These plants are able to produce more roots than shoots. They also have the ability to move their leaves so that only very small leaf area is exposed to radiation. Some also develop hairs on the leaves to insulate the leaf surface or may become waxy (cutin). These characteristics reduce light absorption and therefore water loss. E.g. cowpea and yard long bean. The drought tolerant plants survive drought by functioning normal even with low amount of water in their tissues. Their cells do not collapse even with low amount of water.s