HOW IS WATER LOST TO THE ATMOSPHERE?
Evaporation and transpiration are two natural processes that result in water loss to the atmosphere. Collectively, these two forms are known as evapo-transpiration. Evaporation is water loss from a soil surface while transpiration is water loss from a plant surface.
- What can you do to reduce evapo-transpiration from your fields?
- Plant Windbreaks: A windbreak reduces wind velocities which decreases the rate of evapo-transpiration in the area directly downstream of the barrier
- Keep crop residues on the field: Crop residues reduce the wind-speed at the soil surface which reduces evapo-transpiration; conserve moisture because it shades the soil reducing soil temperatures and solar radiation; and acts as a windbreak at the soil surface
- Choosing Water Conserving Species: Conserve water use in the landscape by not growing too much high water utilizing crops
- Adopting Suitable Crop Rotations
- On-farm Management Practices: There are several on-farm practices which can help conserve water in the soil. These include:
- Increasing organic matter levels: This increases water infiltration and the water holding capacity.
- This can be done through many ways such as reducing tillage, improving cropping rotations, and adding soil amendments.
- Soaking seeds: Improve and speed up germination by soaking seeds before seeding. This is especially valuable for large seeded grain legume seeds like The 4-K Manual – A Guide for 4-K Clubs in Kenya peas. Different seeds need different soaking times, usually not more than 24 hours for most seeds. Seeds should not be soaked until they sprout; sprouting needs to occur in the soil. This practice reduces the need for water irrigation
- Adopt Suitable Irrigation Methods: When irrigation is used, water should be applied efficiently and effectively to make every drop count. Wasted water can cost money and may lead to the salinization of the soil, as well as surface or groundwater contamination.
There are four methods of applying water to fields
- Hand Watering: The direct application of water to the base of the plant uses less water and can be more efficient than sprinkler and flood irrigation
- Drip Irrigation: Also called trickle or micro-irrigation, this method applies water slowly and directly to the roots of plants through small flexible pipes and flow control devices called emitters. It uses 30 to 50 percent less water than sprinkler irrigation
- Sprinkler Irrigation: This method distributes water onto the field through the use of a piping and/ or hose system. Sprinkler heads, located at regular intervals within the piping system, spray water onto the crops. Sprinkler irrigation is more efficient than flood irrigation because it distributes the water more evenly and reduces losses to seepage
- Flood Irrigation: In this system, the field is flooded with water. Flood irrigation has the poorest efficiency rate for water usage
Bucket drip irrigation is a low cost irrigation system that relies on gravity fed water from a bucket rather than a water pump to feed the water to a drip irrigation system. It is ideally suited to small-scale farmers growing vegetables for their own households or for small market gardens. The buckets are mounted on posts 3’ (1m) high, enabling enough water pressure for water distribution under the gravity flow irrigation.
The following is true for Crops and Water Conservation
Crops that are:
- Best for preserving soil moisture – peas and lentils
- Medium for preserving soil moisture – wheat
- Low for preserving soil moisture – cornand sunflowers
- Very low for preserving soil moisture – alfalfa
Characteristics of plants that make them more or less drought tolerant and why?
- Perennials – are not as vulnerable to poor establishment due to dry spring germinating conditions. Their deep roots also allow them to have greater access to water
- Extensive root system – the larger and deeper the root system the more effective the plants are in accessing water held in the soil (i.e. millet)
- Small and narrow leaves – crops with a high stem to leaf ratio and narrow leaves (like millet) tend to resist drought more effectively than wide leaved crops