This series of four fact sheets explore irrigation tools and technologies for small-scale horticulture . These fact sheets were created by the Horticulture Innovation Lab project focused on farmer-led innovation for irrigation in Uganda, which engages in participatory research and development with women and smallholder farmers in Uganda to improve irrigation systems, working within the local context and with a focus on gender issues.

The small-scale irrigation technologies highlighted include:

• Micro furrows
• Micro basins
• Raised furrow basins
• Raised and terraced main canal

Each fact sheet includes illustrations and diagrams for building and using the different irrigation systems.

Micro furrows

Micro-furrows are very short furrows with flat, level bottoms that run along the contour of a slope, filled one at a time to allow water to infiltrate. Unlike traditional furrow irrigation, micro-furrows can be set across a moderate slope. They can be filled using various methods, such as pipes or canals.

The short length (<10 meters) ensures the entire furrow receives approximately the same amount of water, and the flat bottom allows water to infiltrate at an even depth along the entire length of the furrow. This results in a high water use efficiency.

Benefits of micro furrows:

• Very little loss of water below the root zone or running off the field
• Good uniformity of water applied along the furrow
• Requires little equipment to move water through the field
• Can be used to drain water in times of excess rain

Conditions for using micro furrows:

• Crops: most vegetable crops perform well
• Seasons: rainy and dry. Appropriate for year-round cultivation; furrow ends must be opened during rain to prevent flooding
• Slope: mild to moderate. Mild cross-slopes and mild to moderate main slopes
• Water supply: various, including pumped water, piped gravity water, canal-fed

Limitations and challenges of micro furrows:

• This method requires a high up-front labor requirement in digging and carefully leveling the furrows; the system performs poorly if furrows are not level
• Micro furrows are not appropriate for steep land
• Field can be waterlogged during rain if the furrow ends are not opened
• Filling each furrow requires some labor in closing the ends and moving the inflow

 

Micro Basins

Micro basins are small basins for quick application of significant irrigation depth. They are flat, elevated sections of the field surrounded by soil bunds or embankments that hold water inside. These basins allow users to apply large depths of water in a short time, which will slowly infiltrate into the crop's root zone as the water is held inside the basin by the bunds.

Benefits of micro basins:

• Allows quick application of large irrigation depth
• Low cost of equipment required compared to other methods
• System does not require high water pressures
• Enables a long interval between need to irrigate 

Conditions for using micro basins:

• Crops: most vegetables, however, fungal disease is likelier in some crops
• Seasons: dry season. Can enable dry-season production of vegetables, but may lead to water-logging in rainy seasons
• Slope: mild. Constructing on a slope less than 2% reduces labor requirement and minimizes erosion of basins
• Water supply: various water supplies, including piped or canal. Manual irrigation is also appropriate for small basins

Limitations and challenges of micro basins:

• High labor requirement for constructing basins
• Once made, plowing the entire field will destroy basins; basins should be made permanently and only re-shaped by hand
• Can result in moderate pressure for fungal disease in susceptible crops such as tomato
• Can waterlog in rainy seasons; openings in bunds must be made to allow excess water to drain during rain

 

Raised furrow basins for waterlogged areas

Raised furrow basins enable targeting irrigation and effective drainage in waterlogged areas. These are flat beds surrounded by bunds, with drainage canals around the edges. Inside each basin, raised beds and furrows are made for vegetables. These beds can be flattened into basins during rainy seasons for rice production. Raising the beds between canals allows a deeper root area in case of rain, but efficient use of water during irrigation. This system can be used with many kinds of vegetable crops, and with various water supplies.

Benefits of raised furrow basins:

• Adequate drainage in waterlogged areas for a number of vegetable crops, including onion, cabbage, carrot and cowpea
• Lower cost than pressurized systems
• Ease of irrigating compared to flooding and watering cans
• Allows use of waterlogged areas throughout the year

Conditions for using raised furrow basins:

• Crops: most vegetables, however, solanaceous crops such as tomato, eggplant, and potato are susceptible to disease in seasonally waterlogged areas
• Seasons: rainy and dry. Appropriate for year-round production and can be used for drainage and water management during rainy periods
• Slope: mild (less than 2%). Steeper slopes can result in greater erosion rates, especially in sandy soils, requiring additional labor for maintaining furrows
• Water supply: various, especially stream diversions, natural and protected springs, and pumped water

Limitations and challenges of raised furrow basins:

• System requires higher up-front costs in labor than other irrigation systems
• Furrows must be unblocked during rain to avoid the risk of flooding the plot
• Rain and irrigation water may erode furrows and beds, especially in sandy and other loose soils; system requires consistent labor in re-shaping beds and clearing furrows

 

Raised and terraced main canal

This is a main canal for feeding water into irrigation furrows, raised above the level of the field to allow easier control of water into furrows. The canal is terraced to have a minimal slope in each section of the canal. This is done to ensure an even distribution of water through discharge points along the canal. Spiles, or spiggots, are inserted into the sides of the canal to divert water to a plot.

Benefits of raised and terraced main canal:

• Easy control of water into furrows
• No moving of soil, which can damage furrows and canals
• Good uniformity of flow into each furrow
• Little labor required during irrigation
• Can be used in areas with easily eroded soils

Conditions for using a raised and terraced main canal:

• Crops: appropriate for most vegetable crops, bananas and other tree crops
• Seasons: best for dry-season vegetable cultivation
• Slope: mild to moderate. Mild slopes allow for best control of irrigation; faster erosion of furrows and beds can result in steeper sloped areas
• Water supply: various and most viable in areas downslope of water supply (e.g. stream diversion, valley fringe with natural springs, dam)

Limitations and challenges of raised and terraced main canal:

• Need for careful leveling of terraces
• Yearly re-leveling of soil in bottom of canal is recommended to maintain good water uniformity in all spiles
• Making canal walls requires a significant amount of labor, especially if using sand bags (required for loose, sandy soil)
• If spiles are left open without monitoring, plots can become waterlogged