Effect of trees alone or with grasses on halting canal seepage and shallow water table control in saline vertisols

A field experiment was conducted at Agricultural Research Station, Gangavati, Karnataka during 1991–1999 to evaluate the effect of different tree species in halting canal seepage and thus control of shallow water table. Six tree and 3 grass species were tried for the purpose. The effects of trees were monitored either by quantifying the seepage flowing through soils (1991–93) or changes in depth to water table (1995–99). Acacia nilotica was observed to intercept about 86% of incoming seepage when compared with control (no trees) and this was followed by Dalbergia sissoo that intercepted 84% of the flow. Performance of Sesbania grandiflora and Casuarina equisetifolia was almost equal (72%) despite later having only 50% of the canopy area. Other species such as Hardwickea binata and Azardirachta indica showed relatively lower efficiencies (<70%) in respect of control of seepage. Grasses when planted with trees had synergetic effect. Water table depth during 1995–99 receded considerably in the plantation area during both the canal running (from 1.3 to 1.8 m) and canal lean period (from 1.7 to 2.1 m); despite an increasing trend (from 1.0 to 0.7 m during canal running period) observed outside the plantation where field crops were grown. On the whole the studies established the role of trees in lowering water table of marshy lands.