The rise in groundwater table followed by waterlogging and secondary soil salinization is a serious problem in canal-irrigated areas of arid and semi-arid regions. To combat the problem, an agroforestry model for biodrainage was tested in waterlogged fields of Haryana (northwest India), where 10 per cent area (0.44 m ha) is waterlogged resulting in reduced crop yields and abandonment of agricultural lands.
In this model, four parallel strip-plantations of clonal Eucalyptus tereticornis (Mysore gum) were raised in December 2002 on four ridges constructed in the north–south direction in 4.8 ha canal-irrigated waterlogged fields of farmers. The strip-plantations were spaced at 66 m and each strip-plantation contained two rows of trees at a spacing of 1 m × 1 m, resulting in a density of 300 plants ha–1.
Levels of groundwater table were measured over 3 years (April 2005–April 2008) in 22 observation wells installed in two transects across the strip-plantations. The study indicated the following –
- The groundwater table underneath the strip-plantations remained lower than that in the adjacent fields and the drawdown in groundwater table was 0.85 m in 3 years.
- The annual rate of transpiration by 240 surviving trees per ha was 268 mm annum–1 against the mean annual rainfall of 212 mm.
- The strip-plantations sequestered 15.5 t ha–1 carbon during the first rotation of 5 years and 4 months.
- Benefit–cost ratio of the first rotation of strip plantations was 3.5: 1 and it would be many folds for next 3 to 4 rotations due to negligible cost of coppiced Eucalyptus.
- Wheat yield (April 2008) in the interspace of strip-plantations was 3.4 times that in adjacent waterlogged areas without plantation. It was mainly because of lowering of the water table and improvement in soil properties.
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