Effect of open ditch draining on sediment and soil properties in cultivated areas in southeast Mexico

In the last 10 years in many parts of the coastal plain of Tabasco, SE-Mexico open ditch draining systems were installed. From April to October 2003 we investigated the effect of draining on sediment deposition on floodplain soils with agricultural and pasture use. Open ditch draining reduced the amount of sediment deposited on inundated soils. This was due to the fact that the number of inundations that occurred in the drained area was smaller than in natural areas. However, neither the amount of sediment deposited on the floodplain soils after a single inundation nor the nutrients or heavy metals (Zn, Pb) transported with the sediment deposited by a single inundation were influenced by the draining. The total amount of deposition in the drained areas varied from 94.2 to 123.5 t ha− 1 (April to October) and did not show any significant differences between different land uses. In the natural area the deposition was significantly higher (242.6  t ha− 1). Organic matter, Ntot, Ptot and Zntot content of the new sediment did not differ between natural and drained sites. In none of the sediments Pb was detected. However, in the natural area organic matter, Ntot and Ptot content in topsoil increased significantly between April and October 2003 whereas in the drained areas only the Ptot content in topsoil increased. Eighty-five percent of the amount of organic matter and Ntot deposited on the topsoil of the natural area was lost probably by mineralization and lateral transport. The input of Zntot deposited with the sediment in all sites exceeded the trigger value of 1200 g ha year− 1 for critical load inputs in soils [Bundes-Bodenschutz- und Altlastenverordnung, 1999. http://www.fh-kehl.de/projekt_bodenschutz/bundesrecht/BodSchV.htm] due to extremely high quantity of sediment deposition.