Experience around the world has made it clear that soil pitting is often the most cost effective treatment to facilitate recovery of abandoned, barren land. Pits capture water and provide safe sites for seeds, collect litter, and help to protect and water seedlings.
Pitting is relatively easy to do with hand labor and is less noticeable in a restoration project because the pattern can be varied easily, Hand pitting is best done as a communal activity so progress is clearly visible. But it is slow. mechanical pitters are critical to cover large areas.
A wide variety of pitting plows have been developed and used successfully. Australia’s Kimseed Camel Pitter has been available for several decades. It can be pulled by a truck, jeep or camel. The current model of Camel Pitter includes seed metering devices. On our research projects we used a custom built larger disk pitter that had to be pulled by a tractor or large truck. These pits helped speed recovery but for degraded lands even larger pits are desirable.
The answer for larger deeper pits is the Delfino plow and the Vallerani system. Significant progress came with the development of the mechanized system of harvesting surface runoff with the “Vallerani System” (named after its Italian inventor). The first experiments in the development of this approach were carried out in 1988 as part of the Integrated Programme for Rehabilitation of the Damergou (FAI-Niger). Since then work has been carried out in many countries.
The Vallerani system makes it possible to bring hard, compacted soil that had been abandoned because it was impossible to work manually back into production. The Delfino plow has a ripper in front of the plowshare to open and loosen the soil down to 60–70 cm. The ripper also helps protect the plowshare. The rip lines create an underground furrow that can help share the water between adjoining micro basins. Ripping the compacted soil enables deep infiltration of rainwater and more extensive root growth. The rainwater, top soil, seeds, and organic materials transported by the wind and run-off accumulate in the micro basins and along the rip line, facilitating recovery. The reversible plowshare allows for efficient tractor operation. The tractor mounted plow can typically treat 1.5-3 hectares per hour.
These soil pits make a difference. Experiments have found 2 to 4 times more water available for crops, pastures, and plants with improved survival and growth and recovery of biodiversity. In areas with excessive bare soil with no seed sources it is desirable to add seeds to the basins. These can be nitrogen fixing multipurpose tree or shrub species like ratam and olives (in the Mideast), honey mesquite (in SW North America), and neem (in Mali). Planting appropriate seedlings in the pits can create more rapidly established islands of fertility. The VS allows for direct seeding whose germination and growth is possible thanks to the water collected in the micro-basins and the improvement in soil physical characteristics. Images of the recovery possible with the VS are striking.
The larger tractors and Delfino plows will require maintenance and technical support. Each tractor (200 hp) might cost US$50-200,000 and the Delfino plow from Nardi might cost another $40,000. Hommes et Terre offers the Vallerani treatment as a service rather than selling the plow/system in Mauritania, Senegal, Mali, Burkina Faso, Niger, Chad, Gambia and Benin. Overall treatment costs might be on the order of US$100 hectare plus the cost of seeds and/or seedlings. Adding organic material, compost, or mulch can also be helpful but adds to the cost. This made a difference in our studies of soil pitting.
Hommes et Terre is a Belgian-African company with a social mission to restore degraded land, ensuring that communities have sustainable access to productive land. Their economic model is to develop profitable and sustainable agroforestry systems in an equitable collaboration with local communities. Hommes et Terre develops their own projects through the Project Forests Villages (PFV) program. This innovative program is based on intensive, equitable and sustainable collaboration with villages. Hommes et Terre enters into 25 year relationships with village partners.
Further reading
Ali, A., T. Oweis, A. Abdul Aal, M. Mudabbar, K. Zubaidi, and A. Bruggeman. 2006. The Vallerani Water Harvesting System. ICARDA Caravan No. 23, December. pp 13-15.
Bainbridge, D. A. 2024. Initiating recovery of degraded dry lands with soil pitting. SW Chapter Conference, Tucson. September. 6 pages. https://www.youtube.com/watch?v=ctsR7GeKy-w
Bainbridge, D. A. 1993. Soil pitting: a technique to improve arid land revegetation. Soil Ecology and Restoration Group, San Diego State University. Bulletin #1. San Diego, CA 7 p. https://www.academia.edu/3796575/1993_Soil_pitting_for_land_restoration
Conedera, M., N. Bomio-Pacciorini, P. Bomio-Pacciorini, L. Sciacca, S. Grandi, A. Boureima, and A. M. Vettraino. 2010. Reconstitution des écosystèmes dégradés sahéliens. XX: Bois et Forêts des Tropiques. 304(2): 61-71. http://bft.cirad.fr/cd/BFT_304_61-71.pdf
Food and Agriculture Organization of the United Nations. 2015. Global guidelines for the restoration of degraded forests and landscapes in drylands: building resilience and benefiting livelihoods. Forestry Paper No. 175. Rome: FAO. https://www.fao.org/3/a-i5036e.pdf
Gammoh, I. A. and T. Y. Oweis. 2011. Performance and adaptation of the Vallerani Mechanized Water Harvesting System in degraded Badia rangelands. Journal of Environmental Science Computer Science and Engineering & Technology. October. 5:1370-1380.
Gammoh, I. A. and T. Y. Oweis. 2011. Contour laser guiding for the mechanized “Vallerani” Micro-catchment Water Harvesting Systems. Journal of Environmental Science and Engineering. 5 (2011) 1309-1316.
ICARDA. nd. Recovering the Degraded Soils of the Badia in Jordan. https://www.icarda.org/research/innovations/recovering-degraded-soils-badia-jordan.
Tamura, M., T. Y. Oweis, V. Nangia and S. Strohmeier. 2021. Managing scarce water resources in the drylands of West Asia and North Africa: Review of Joint Research between ICARDA and Japanese Researchers. Japan Agricultural Research Quarterly JARQ 55 (SI), 511-519. https://www.jircas.go.jp
Whitesides, A. and K. Clingen .2023. Vallerani Micro Water Harvesting Department of Landscape Architecture Course. Climate by Design, Fall. (https://www.gsd.harvard.edu/course/climate-by-design-fall-2023/)
