Effect of forage grass (Pennisetum pedicellatum) and legume
(Stylosanthes hamata) revegetation on recovery of soil fertility in a
reclaimed hazardous waste dump
Abstract
Dumping of hazardous waste causes land degradation, air, and water
pollution, deteriorates landscape and aesthetics, which can be
controlled by reclaiming with grass-legume seeding. The study aimed to
examine the effect of grass-legume revegetation between 1- and 5-years
in a restored waste dump (hazardous waste of an integrated steel plant)
reclaimed with coir-matting, topsoil blanketing followed by grass
(Pennisetum pedicellatum) and legume (Stylosanthes hamata) seeding. We
hypothesized that the synergistic effect of the grass-legume mixture
would lead to an increase in productivity and soil fertility. To assess
the effects, changes in root and shoot biomass, mulch accumulation,
nitrogen (N) mineralization, and its effect on soil fertility were
measured. Our results showed between 1- to 5-years legume and grass
biomass increased by 44% and 37%, respectively. An increase in mulch
density and thickness along with revegetation age potentially increased
the soil moisture by 7.5% and lowered soil temperature by 9°C at 10 cm
depth. Cumulative N-mineralization by legume was three-fold higher than
the grass. Soil organic carbon (SOC), available N, total N, N-stock, and
soil respiration was doubled after 5-years of revegetation.
Dehydrogenase and urease activity increased by 44% and 56%
respectively, indicating greater C and N accumulation at the dump
surface. The study concluded that grass (P. pedicellatum) and legume (S.
hamata) mixture can be used for reclamation of the waste dump that
accelerates recovery of the fertility of disturbed topsoil by
contributing mulch with increasing age of revegetation.