Restoration of degraded sodic soils through silvipastoral systems in the Indo-Gangetic Plains

Excessive salts in degraded sodic soils aggravate the bio-physicochemical properties of soils that need to be remediated and restored in a judicious way. The present study envisages smothering harmful effects of sodic soils and maintaining soil fertility through need-based silvipastoral systems. We report on a three-times replicated field experiment with 13 treatments comprised of three agroforestry tree species Acacia nilotica, Casuarina equisetifolia, and Eucalyptus tereticornis planted during 2005 on highly sodic soil of pH 10.6 and exchangeable sodium percentage (ESP) of 89 in the Indo-Gangetic Plains. Fodder grass species viz. Chloris gayana, Panicum maximum, and Pennisetum purpureum were planted under each of the 10-year-old tree species. The maximum biomass production of understory grasses was recorded from A nilotica + C. gayana silvipastoral system while the highest nutritive value in terms of N. P, K, and crude protein content (%) was recorded in A. nilotica + P. purpureum. A strong correlation between photosynthetically active radiation (PAR) and understory grasses was observed. Significantly higher tree growth and biomass yield were recorded under silvipastoral systems over silvicultural system. A significant reduction in soil bulk density and increase in soil porosity, infiltration rate, and water holding capacity (WHC) were recorded in silvipastoral systems over silviculture and control due to reduced sodicity, addition of leaf litter, increase in microbial activities due to tree and grassroots, better plant growth, and fine root decay. Reduction in soil pH, exchangeable sodium percent (ESP), and increase in soil organic carbon were more pronounced under silvipastoral systems over the silviculture. The highest reduction in these parameters was recorded under the A. nilotica + C. gayana silvipastoral system. Similarly, soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP), and dehydrogenase activities were higher under silvipastoral systems over the silvicultural system The highest MBC was recorded in C. equisetifolia + C. gayana which was 302.8% higher than the control. However, highest MBN and dehydrogenase activities were recorded under A. nilotica + C. gayana silvipastoral system. Hence, on the basis of total biomass yield and improvement in soil bio-physicochemical properties A. nilotica + C. gayana silvipastoral system could be a highly ameliorative and productive system for the restoration of degraded sodic soils.

Automated summary

Excessive salts in degraded sodic soils exacerbate soil properties, which need to be remediated and restored in a judicious way. This study aimed to mitigate the harmful effects of sodic soils and maintain soil fertility through need-based silvipastoral systems. The results demonstrated that different tree species and grasses significantly influenced soil properties and plant growth, with the A. nilotica + C. gayana silvipastoral system being the most effective for restoring degraded sodic soils.