Soil Nutrient Status and Greenhouse Gas Emission in Major Agroforestry Systems of South India
Agro forestry systems play a predominant role in the global carbon cycle by restoring carbon stock in the
ecosystem and reducing greenhouse gas (GHGs) emissions from soil. The impact of major plantation agroforestry systems
in South India viz. rubber, tea, coffee and cardamom on soil nutrient availability and GHG emission was investigated.
Representative soil samples were collected and analysed for total and available nutrients, CEC and pH.For examining
temporal and seasonal changes in soil respiration (Rs), insitu carbon dioxide (CO2) flux rate in each system was recorded by
using an automated soil respiration analyser. Static closed chamber method was used to measure methane(CH4) and nitrous
oxide(N2O) emission from agroforestry systems and the collected gas samples were analysed using gas chromatography.
Significant difference in soil nutrient status and GHG emission was observed among different agroforestry systems. The
high biomass addition, nutrient enrichment of soil through fertilizers and liming materials contributed to significantly high
per cent of total carbon (TC), organic carbon (SOC), nitrogen (TN), available calcium (Ca), magnesium (Mg) and pH in
coffee agroforestry system. Tea agroforestry system had high per cent of available soil phosphorus (P) and potassium (K).
The Rs varied spatially, temporally and seasonally among different systems and was higher in summer season followed by
winter. Among the systems studied, the highest rate of Rs was detected in cardamom and coffee system and lowest in rubber.
Nitrous oxide (N2O) and methane (CH4) gases were undetectable in all agroforestry systems during the period of observation.
Significantly positive correlation of Rs with soil temperature was observed in all systems. The lower per cent of the total and
available soil nutrients were observed in rubber agroforestry system, which might be due to the lower altitude of the system
compared to other systems. The results of the study indicated that the altitude, land use pattern and management practices in
agroforestry systems significantly influenced the total and available soil nutrients status and GHG emission from soils.
Index Terms - Agroforestry Systems, GHG Emission, Soil Nutrient Status, Soil Respiration