Abstract
ABSTRACT Increasing land demands for food production has led to large-scale soil degradation in the hilly regions of south-eastern Bangladesh. An intensification of slash-and-burn techniques, where fallow intervals have shortened considerably in recent years, has led to widespread losses in soil quality. Here we sought to test to what extent do current agroforestry practices in the area, compared with current reforestation efforts, can ameliorate different physicochemical soil properties after the abandonment of slash-and-burn practices. We observed that concentrations of soil organic matter (4.75%), available phosphorous (12.17 μg g−1) and exchangeable potassium (0.39 mg kg−1) in agroforestry plots were significantly higher than in reforestation (3.18%, 6.50 μg g−1 and 0.21 mg kg−1, respectively) or slash-and-burn plots (1.83%, 5.90 μg g−1 and 0.03 mg kg−1, respectively). While reforestation and agroforestry may both serve to restore soil functions but we observed higher benefits in the latter system. Thus, agroforestry systems may be a suitable land management system for replacing ancestral slash and burn techniques but care should be taken to diminish soil compaction.
Highlights
One of the main challenges during the 21st century will be to ensure food supply while avoiding large-scale land degradation under global change
In case of soil physical properties, dry bulk density (DBD) and moist bulk density (MBD) were significantly higher in agroforestry plots (1.35 g cm−3 and 1.42 g cm−3, respectively), than in denuded slash-and-burn hills (1.20 g cm−3 and 1.24 g cm−3, respectively) or than in adjacent forest plantations (1.08 g cm−3 and 1.17 g cm−3, respectively), whereas there was no significant difference in DBD or MBD between the forest plantation and the denuded hills (Table 2)
We observed no significant differences in soil moisture content (MC) between the agroforestry plots (5.62%) and the denuded hills (3.64%), but soil MC was significantly higher in forest plantations (8.43%) (Table 2)
Summary
One of the main challenges during the 21st century will be to ensure food supply while avoiding large-scale land degradation under global change. In many areas globally, including Bangladesh, land degradation has been increasing at an alarming rate Ancestral management techniques, such as slash-and-burn, are under pressure to provide support for an increasing population (Biswas et al, 2012; Suryatmojo, 2014). This has led to the shortening of the fallow period from 15–20 years in the 1900 s to just to 3–5 years nowadays. The Chittagong Hill Tracts (CHTs) from south-eastern Bangladesh are sensitive to soil degradation because the area is characterized by steep slopes, often reaching above 40%, which may increase soil erosion and, soil fertility losses (Lenka et al, 2012). Annual crop production by slash-and-burn practice in steep slopes adversely affected the forest genetic resources and hampered ecosystem functioning (Biswas et al, 2012; Haque et al, 2014)
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