Soil carbon pools as affected by the history of agricultural land use of calcic red tatosols in Jaffna
Date
2013-07-04
Authors
Ajanthini, S.
Dandeniya, W. S.
Journal Title
Journal ISSN
Volume Title
Publisher
The University of Peradeniya
Abstract
The agriculture sector is growing in the Jaffna district in Sri Lanka. Mismanagement of agricultural lands could lead to soil degradation. Soil organic carbon (SOC) is a key determinant of soil fertility. Information on the quantity and quality of carbon pools will be useful in formulating long term plans to manage soil fertility. A study was conducted to compare SOC pools in different land-use histories in Jaffna and to assess the activity of organic-matter decomposing microorganisms in the respective soils.
Land-uses on calcic red yellow latosol with no-cultivation history (A), and history of cropping with organic amendments only (B and C), inorganic amendments only (D) and both amendments (E) were selected. Soil was sampled from 0-15 cm depth, air-dried and brought to University of Peradeniya and passed through a 2 mm sieve. Soil was analyzed for SOC using loss on ignition (LOI) and Walkley and Black methods, particulate organic-matter (POM), active-carbon (AC), inorganic-carbon, and potential mineralizable nitrogen (PMN). Soil respiration was determined after bringing soil moisture content to 25% (w/w). To assess the activity of SOC decomposing microorganisms, the response to organic inputs with different complexities was determined. For this, subsamples from each land-use history were incubated with rice-straw, poultry manure (PM) and glucose (2%, w/w), and soil respiration was measured for 2 weeks. Data were statistically analyzed using SAS 9.1.3 software.
In cultivated sites (B – E), pH was neutral, EC ranged from 419 to 620 μS/cm and cation exchange capacity (CEC) ranged from 20.3 to 33.3 cmol+/kg. At site A, pH, EC and CEC were 7.75, 168.4 μS/cm and 12.8 cmol+/kg, respectively. CEC was positively correlated with SOC (r2= 0.8, p<0.05). SOC pools varied across land-use histories. Application of organic manure caused significantly higher SOC and AC contents. Uncultivated site A had a higher basal soil respiration (1.21 μg <formula>/g/wk) than cultivated sites (ranged from 0.55 to 0.88 μg <formula>/g/wk). PMN was different across land-use histories (2 – 8 μg N/g/wk) and hence the quality of labile SOC. Amending uncultivated soil with PM decreased respiration by 50% but respiration increased by more than 10% with the same treatment in other land-uses with a history of organic manure usage. Increase in respiration rate in response to amending soil with glucose, rice-straw and PM was positively correlated with AC (r= 0.6, 0.6 and 0.7) and POM (r= 0.5, 0.5, and 0.6). History of land-use affects the quantity and quality of soil carbon pools and organic carbon decomposing microbial communities.
Description
Keywords
Climate and Environment , Calsic red latosols , Soil carbon pools , Agricultural land , Jaffna
Citation
Peradeniya University Research Sessions PURSE - 2012, Book of Abstracts, University of Peradeniya, Sri Lanka, Vol. 17, July. 4. 2012 pp. 02