Ploughing and planking in spate irrigated areas

In spate irrigated areas (Pakistan, Eritrea and Yemen) the combination of ploughing prior to and after irrigation are important soil moisture conservation measures. Breaking the topsoil through ploughing land prior to irrigation greatly increases infiltration rates with initial infiltration rates for Wadi Rima in Yemen increasing from 40 to 60 mm/hour (van Steenbergen et al., 2010). Pre-irrigation ploughing also makes cultivation much easier and quicker to carry out once the floodwaters arrive, which is important, as a great deal of labour is required to cultivate the land after irrigation (Williams, 1979). Having captured as much water during the spates farmers then need to make sure that the water does not evaporate or is lost to deep groundwater. The common recommendation then is not to delay ploughing for more than two to three weeks, to avoid water loss through evaporation or deep percolation. Research in Yemen suggests that, if land is not ploughed within two weeks after irrigation, up to 30–40 percent of the moisture may be lost.

Following the ploughing seeding can take place which in certain spate irrigated areas is followed by planking. Which by means of bullock or tractor drawn planks (weighed down by people) ensures modest compaction of the top soil (<10cm) and further reduces evaporation; essential for ensuring soil moisture retention during the first planting stage.

References

van Steenbergen, F., Lawrence, P., Mehari, A., Salman, M., & Faurès, J.-M. (2010). Guidelines on spate irrigation (Irrigation). FAO. http://www.fao.org/3/i1680e/i1680e.pdf.

Williams, J.B. (1979). Yemen Arab Republic. Montane Plains and Wadi Rima Project: a land and water resources survey. Physical aspects of water use under traditional and modern irrigation/farming systems in Wadi Rima Tihama.

Additional sources

Saeed Khan, R., Nawaz, K., van Steenbergen, F., Nizami, A., Ahmad, S., 2014. The Dry Side of the Indus. Exploring Spate Irrigation in Pakistan.