Tree-based farming systems for improving productivity and ecosystem services in saline environments of dry regions: An overview

Abstract

Degraded salt-affected lands are reported to occupy 1257 million hectares worldwide, representing about 8.5% of land area in 118 countries along with a large area lying barren in arid and semi-arid regions due to lack of good-quality water for irrigation because of saline underground aquifers. Several long-term field experiments carried out in different countries have shown that combining salt-tolerant multipurpose trees with forage grasses, arable and under-explored crops (including aromatic and medicinal plants) using suitable technologies can contribute to a significant improvement in agricultural production without applying costly amendments in sodic lands and sub-surface drainage systems in saline-waterlogged soils. The objective of this review is to discuss salinity constraints to crop production, technological interventions for the tree–based systems, and site-specific systems for enhancing productivity and ecosystem services. Salt-tolerant multi-purpose trees, grasses, high-value halophytes, and commercial crops provide numerous provisioning services including food, fodder, fuelwood, bio-energy, cash crops, and medicinal plants. Bioamelioration of sodic soils, diversity of AM fungi, nutrient cycling, variable litter decomposition rates, and carbon sequestration contribute to enhanced regulatory services. The AM fungal association with fertiliser trees like Prosopis cineraria, and salt-tolerant grasses of sodic soils enhances nutrient cycling. The soil microbial biomass carbon and soil enzyme activities serve as a good indicator of the bio-amelioration of salty lands. Carbon (C) sequestration rates in trees and mallees in South Australia are reported to be 1.73–3.8 ​Mg ​C ha−1 yr−1; C stock in soil (6.839–27.09 ​Mg ​C ha−1) and soil micro-aggregates increased in tree-based systems in north-west India. Soil inorganic C formed 50–78% of total soil C stock in the traditional agroforestry systems in arid regions. The inorganic C stock in semi-reclaimed sodic soil was 157.3 ​Mg ​C ha−1 in a 25-year-old Grevillea robusta plantation.