Field evaluation of unsteady drain spacing equations for optimal design of subsurface drainage system under waterlogged vertisols of Maharashtra

The field experiment was conducted at Agricultural Research Station, Kasbe Digraj, Dist. Sangli during Adsali sugarcane season of 2012–13 to 2013–14. The experiment was conducted by installing subsurface drainage system with 10, 20, 30 and 40 m drain spacing and 1 m drain depth. In view of different costs and effectiveness of subsurface drainage associated with the varying depths and spacings, field evaluation of unsteady drain spacing equations was important for finding out the optimal drain spacing equation among various equations. The field evaluation of unsteady drain spacing equations revealed that the van Schilfgaarde, Hammad, Modified Glover, Guyon and Integrated Hooghoudt's equation performed satisfactory for estimation of water table depths among seven unsteady drain spacing equations. The Glover-Dumm and Modified Glover-Dumm's equations were not performed satisfactory for estimation of water table depths. Among unsteady drain spacing equations, van Schilfgaarde's equation performed better and hence recommended for water table depth estimation and in turn for optimal design of subsurface drainage system under waterlogged vertisols of Maharashtra.