Microbial and Enzyme Activities and Carbon Stock in Unique Coastal Acid Saline Soils of Goa

Abstract

The aim of the present investigation was to study the effects of salinity under low soil pH conditions on soil microbial and enzyme activities and to quantify soil organic carbon (SOC) stocks in coastal saline soils of Goa, India. Global positioning system based replicated soil samples collected from fifteen different locations showed characteristic variations in electrical conductivity (0.09-6.29 dS m -1 ), soil pH (4.11-6.57), exchangeable sodium (Na) (7.40-23.2 meq 100 g -1 ) and exchangeable sodium percentage (48.3-85.7 %). Exchangeable Na was the most dominant cation among all the cations analyzed at all the sites. The total SOC stock of the study sites varied significantly (p \ 0.05) and ranged from 4.27-24.3 Mg C ha -1 . The soil microbial activity measured in terms of basal soil respiration, soil microbial biomass carbon (C mb ), C mb as a fraction of SOC and enzyme activities related to dehydrogenase, phosphatase and urease showed a decline with increasing salinity levels. On the contrary, metabolic quotient increased with increasing salinity. The results of the study suggest that salinity under low soil pH has a depressive effect on the soil microbial and enzyme activity. Alleviation of the depressive effect of salinity on microbial activity needs to be addressed through suitable interventions and countermeasures for sustainable crop production in coastal acid saline soils of Goa.

Spatial and temporal variability in microbial activities of coastal acid saline soils of Goa, India

“…The qCO 2 of strongly saline soils was 2.4 times higher than that of non-saline soils. The occurrence of higher qCO 2 with high salinity levels has been reported in literature by researcher (Mahajan et al, 2015;Iwai et al, 2012;Tripathi et al, 2007) and our observations are in line with them. Chowdhury et al (2011) and Setia et al (2011) reported the decrease in BSR with increasing levels of salinity and this trend was similar even after addition of organic matter.…”

“…Besides the physical properties of the soil, the biological properties serves as a better indicator of soil quality and one such biological properties is MBC (Mahajan et al, 2015). Inverse relationship of the salinity with MBC, during all the seasons, is in line with those reported by Tripathi et al (2006), Iwai et al (2012), and Mahajan et al (2015). The range of the MBC in the present investigation is 21.1 to 112.8 mg kg −1 .…”

“…The results clearly indicated the detrimental effect of the salinity on microbial activities. The significant reduction of MBC/SOC due to high salinity also recorded by Egamberdieva et al (2010) and Mahajan et al (2015), may be related to microbial stress by higher organic consumption per unit MBC to maintain the cell integrity and release the Na + . These both processes consume and require metabolic energy (Utsugi et al, 1998).…”

“…The values of MBC/SOC in the strongly saline soils (0.59 %) are close and in line with those reported by Sardinha et al (2003) under strong saline soils (0.50 %). The adverse effect of the soluble salts and osmotic stress could have caused inhibition of the C assimilation by microorganisms (Mahajan et al, 2015).…”

“…This explains the magnitude of the salinity effect on microbial activity. The qCO 2 is an indicator of the environmental stress on the microbial community (Reitz and Haynes, 2003;Rasul et al, 2006;Iwai et al, 2012;Mahajan et al, 2015). The reduced qCO 2 in high salinity levels indicates the lower microbial functioning efficiency (Anderson and Domsch, 1989) and it also implies that relatively high C has to be allocated by the microorganisms for maintenance than growth.…”