Chapters 5.70

5.70 -Porous Pots to Irrigate Fruit Trees

Joelle Connolly , University of Guelph, Canada

Suggested citation for this chapter.

Connolly,J. (2022) Porous Pots to Irrigate Fruit Trees, In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

Porous Pots to Irrigate Fruit Trees

Successfully growing and harvesting tree fruits is a challenge for many smallholder farmers, as many are located within regions of poverty that are dry, hot and have unpredictable climatic obstacles with limited access to water (Bainbridge, 2001). An effective method that has been used for centuries to irrigate fruits trees in dry regions is the porous pot (Bainbridge, 2001). Typically, this is an orange terracotta pot or referred to as an olla (Permaculture, 2018) (Figure 1). A porous clay pot is filled with water and buried next to fruit trees to irrigate them (Figure 2).

Porous pots are made from clay material which naturally forms micropores -- tiny holes that function as natural water dispersion/drainage for the plant (Permaculture, 2022). When being made, the wet clay is baked at high temperatures to produce a dry unglazed pot. Pot based irrigation systems used are either buried within the ground or are sub-buried leaving the pot partially exposed (Permaculture, 2022). The method selected by farmers is based on what is best for that crop. Fruit trees grow best in subsurface buried pots (Woldu et al., 2015). Porous pots represent a low input system which releases water slowly, based on the needs of the plant and soil moisture content. A potted crop system would be suitable for areas with low rates of precipitation levels of less than 500 mm of rainfall per year (Woldu et al., 2015). Many dry regions have soil with a high saline content, leaving farmers with poor-quality soil; however, the clay balances the pH of the soil and plants (Bainbridge, 2001).

How to use porous pots

Before planting, farmers must determine the size number of pots needed per crop. Pot selection is based on pot volume needed per unit area of land (m2); approximately 5 L/m2 should be considered. The process of planting is relatively easy and has minimal steps:

Steps:

1. Obtain the porous pot. Soak the pot in water for 3- 24 hours to prepare the pot for a plant which allows the clay material to “breathe”.

2. Empty the water in the pot after soaking; the pot will become dark in color when it is ready for use.

3. Once the pot is primed for planting, obtain soil and transplant or sow seeds of choice.

4. Dig a hole in the ground and place the pot subsurface beside the plant, leaving <5cm of the pot exposed).

5. Fill the pot with water, then place an adhesive cover stone on the opening of the pot if it is sub-buried.

6. Repeat watering every 24 hours until the plant is ready to be harvested

7. The pot may need to be replaced every 3-4 years.

Understanding the product and critical analysis

Drip irrigation functions via the microporosity of the pot and slowly releases water to the soil directly surrounding the plant (Permaculture, 2022). The “pores” of the pot allow for moisture levels to be self-regulated when the water content is high or low (Woldu et al., 2015). Once a pot has been buried and is watered/fertilized, excess water diffuse out via the pores, but it stops when the plant reaches maximum absorption capacity (Woldu et al., 2015). This self-sufficient drip irrigation system prevents the need foradditional, expensive water systems such as pressured water pipe systems, sprinklers, or automated watering technologies (Woldu et al., 2015). A porous pot must have an appropriate number of pores with a diameter that allows for water to exit and oxygen to circulate, as improper irrigation results in water stress/nutritional stress on the plant (Bunt et al., 1970). The structural design of pores prevents drainage clogging (Woldu et al., 2015).

Porous pots offer numerous benefits to farmers. The clay material used is sustainable, accessible, and easy to harvest. Clay has insulating properties that efficiently utilize energy from the sun. Clay also promotes the growth of the plant by providing a healthy environment that supports the plant and soil microbes. Unfortunately, the contained water and humidity increase the risk of bacterial growth (Budelo et al., 2018). Bacterial growth can be harmful due to the formation of a biofilm on the pot’s interior surface (Budelo et al., 2018). Additionally, clay contains minerals, including silver or iron which prevents bacterial overgrowth. Silver is advantageous because it inhibits the growth of bacteria that may be pathogenic to the plant (Budelo et al., 2018). Silver contains nanoparticles that inhibit bacterial growth as a disinfectant, disrupting bacterial replication and cell structure (Budelo et al., 2018). Iron benefits the plant as it stores thermal energy and contains nanoparticles that are reactive with oxygen which promote plant growth (Budelo et al., 2018).

However, there are a few additional limitations to consider. Carrying heavy clay pots and digging large holes may be too physically demanding for some farmers. Pot capacity may limit farmers if the volume is inadequate to support plant growth. Regardless of limitations, a porous pot is very simple to use, requiring minimal training and hence represents an appropriate technology for small scale farmers. Finally, many smallholder farms already have good access to clay pots or the materials needed to make them.

Why Porous Pots for Fruit Trees

Many farmers that plant fruit trees reside in unpredictable climates where the soil is dry and high in minerals. Fruit trees have large root systems that radiate horizontally from the tree trunk. Porous pots can drip water onto these root systems and provides fruit trees with a continuous water source. Porous pots with a volume greater than 12 liters is sufficient for a single fruit tree (Woldu et al., 2015). As the fruit tree grows alongside a porous pot, a self-regulated watering system between the tree, soil, and pot forms (Woldu et al., 2015).

How to Implement Porous Pots on Smallholder Fruit Tree Farms

Implementation on smallholder tree fruit farms is dependent on cost, accessibility to local resources/aids, and what crop species is being planted. Most smallholder farmers are poor, and dealing with unpredictable environmental circumstances or scarce agricultural resources. Fortunately, porous pots are low-cost and affordable ($10 - $12 USD or less) and can be purchased from local vendors (Woldu et al., 2015). Local organizations can partner with the International Center for Agricultural Research in the Dry Areas (ICARDA) which provides land, soil, and water management tools to struggling farmers (ICARDA, 2024). The assistance of ICARDA can equip farmers with knowledge of agronomic topics and how to use porous pots. Understanding the function of porous pots, water management, and soil science is critical for introducing this new farming practice (ICARDA, 2024).

Helpful resources to get started

Farmer Training Manual of Porous Pot Irrigation https://www.fao.org/family-farming/detail/en/c/1401660/#:~:text=With%20pitcher%20irrigation%2C%20round%20porous,seep%20out%20from%20the%20pot.

Quick video demonstrating an easy way to plant a buried porous pot and irrigation explanation https://www.youtube.com/watch?v=0MDQsydIGlg

Additional reading resource providing information about use of ollas as an irrigation method https://www.permaculturenews.org/2022/11/29/irrigation-with-ollas/

References

1.Bainbridge, D.A (2001). Buried clay pot irrigation: a little-known but very efficient traditional method of irrigation. Agricultural Water Management 48(2), 79 -88. https://doi.org/10.1016/S0378-3774(00)00119-0

2.Budeli, P. Moropeng, C. Mpenyana-Monytasi, L. and Momba, N. (2018). Inhibition of biofilm formation on the surface of water storage containers using biosand zeolite silver-impregnated clay granular and silver-impregnated porous pot filtration systems. PLoS one, 13(4), e0194715. https://doi.org/10.1371/journal.pone.0194715

3.Bunt, A.C and Kulwiec, Z.J. (1970). The effect of container porosity on root environment and plant growth: 1. Temperature. Plant and Soil, 32(1), 65–80. http://www.jstor.org/stable/42933077

4.ICARDA. (2024). Soil, Water, and Agronomy. ICARDA. Retrieved from: https://www.icarda.org/research/soil-water-and-agronomy

5. Kondo, T. Ikazaki, K. Koala, J. and Takenake, k. (2022). Effects of porous material and irrigation frequency on the survival rate and vegetative growth in mango seedlings at Burkina Faso. Trop. Agr. Develop. 66(3). 89-94.

6.Permaculture. (2018). How to make your garden drought proof using unglazed clay pots. Retrieved from: https://www.permaculturenews.org/2018/12/25/how-to-make-your- garden-drought-proof-using-unglazed-clay-pots/

7.Permaculture. (2022). Irrigation with ollas. Retrieved from https://www.permaculturenews.org/2022/11/29/irrigation-with-ollas/

8.Woldu, Z. (2015). Clay pot pitcher irrigation: a sustainable and socially inclusive option for homestead fruit production under dryland environments in Ethiopia (a partial review). Journal of Biology, Agriculture and Healthcare 5(21), 157 - 167.