Sodic soil reclamation potential of Jatropha curcas: A long-term study

Abstract

Jatropha curcas L. (JCL) has been identified as a biodiesel plant globally. Efforts are underway to domesticate JCL for high seed yield. The plant has potential to grow on marginal/degraded/substandard lands to avoid competition with food crops, but little is known about its potential to reclaim degraded lands. At this study, several accessions of JCL were planted in 2005 on sodic soil to assess soil amelioration potential of the plant. After six years (2011) of plant growth, seed yield was not economically viable; however, soil properties improved significantly when compared to initial (0-year plantation) soil properties at 0–15cm soil depth. Random soil samples were collected from 0 to 15cm soil depth beneath and outside canopies of JCL with high, medium and poor growth in the year 2008 (3-year plantation) and 2011 (6-year plantation). Soil bulk density, pH, electrical conductivity (EC) and exchangeable sodium percentage (ESP) decreased and soil organic carbon (SOC), nitrogen (N), phosphorus (P), microbial biomass (MB-C, MB-N and MB-P) and enzyme activities (dehydrogenase, β-glucosidase and protease) increased significantly with effect of JCL plantation. Significant decrease in soil pH, EC and ESP has been noticed from 8.6 to 7.6, 1.29 to 0.98dSm−1 and 20.7% to 13.8%, respectively. Similarly, soil fertility parameters like SOC, MB-C, dehydrogenase, β-glucosidase and protease increased significantly from 4.55 to 8.41gkg−1, 98 to 352μgg−1, 16.3 to 51.2μgTPFg−1h−1, 75.8 to 338.2μgPNPg−1h−1 and 43.7 to 163.2μgTyrosineg−1h−1, respectively after 6 years of JCL cultivation on sodic soil. Changes in soil properties were significantly higher beneath the canopy than outside canopy. Soil sodicity parameters (bulk density, pH, EC and ESP) and fertility attributes (SOC, N, P, MB and enzymes) were significantly negatively and positively correlated with the height, biomass and litter fall of JCL, respectively. Furthermore, to test whether changes in soil properties are induced by test crop, changes were compared with Prosopis juliflora plantation of same age, which is generally planted for amelioration of sodic soils. The significant decrease in soil sodicity and increase in soil fertility conclude that JCL is equally good to reclaim the sodic soils.