engleski

Soil carbon loss by soil respiration under different tillage treatments

Soil carbon stocks are highly vulnerable to human activities (such as tillage), which can decrease carbon stocks significantly. These activities break down soil's organic matter and some carbon is converted to carbon dioxide (CO2). A part of CO2 (a greenhouse gas that is one of the main contributor to global warming) is lost from the soil by soil respiration (soil CO2 efflux). The aim of our study is to determine the soil carbon loss by soil CO2 efflux under different tillage treatments. The experimental site is characterized by continental climate. Field experiment with six different tillage treatments usually used in this area was set up on Stagnic Luvisols in Daruvar, central lowland Croatia in 1994 with investigation aim on determination of soil degradation by water erosion and later, in 2011, expanded to the research on soil CO2 efflux. Tillage treatments differed in tools that were used, depth and direction of tillage. Tillage treatments were: black fallow (BF), ploughing up/down the slope to 30 cm (PUDS), no-tillage (NT), ploughing across the slope to 30 cm (PAS), very deep ploughing across the slope to 50 cm (VDPAS) and subsoiling (50 cm) plus ploughing (30 cm) across the slope (SSPAS). Field measurements of soil CO2 concentrations were conducted during one year (n = 14) from November 2011 till November 2012, when cover crop was corn (Zea mays L.). Preliminary soil sampling for determination of soil total carbon content was conducted in April 2011. This paper presents results of soil total carbon content in the soil surface layer (0-30 cm), the variations of CO2-C efflux during the year, soil carbon loss by CO2-C efflux and correlation between soil total carbon content and CO2-C efflux. The range of soil surface total carbon content varied from 19 083, 7 kg/ha at BF treatment up to 31 073, 6 kg/ha at SSPAS treatment. The treatment with the lowest average measured CO2-C efflux was BF. The average CO2-C efflux at BF treatment was 7, 9 kg CO2-C/ha/day where CO2-C efflux varied from 2, 3 kg CO2-C/ha/day up to 22, 6 kg CO2-C/ha/day. The treatment with the highest average measured CO2-C efflux was NT. Range of CO2-C efflux at NT treatment varied from 7, 8 kg CO2-C/ha/day up to 65, 8 kg CO2-C/ha/day and the average CO2-C efflux was 24, 4 kg CO2-C/ha/day. Daily soil total carbon loss by soil respiration ranged from 0, 04% at BF treatment up to 0, 09% at NT treatment. Soil CO2-C efflux was fully positively correlated with soil total carbon content (r=0, 91). After all mentioned, it can be said that in these agro-ecological conditions, best tillage practice in sustainable plant production in terms of the lowest daily soil total carbon loss (0, 06%) by soil respiration is ploughing to 30 cm (PUDS and PAS). Still, it is necessary to conduct the total soil carbon balance in the future research for better understanding of soil carbon gains and losses.

soil carbon loss; soil respiration; CO2 - C efflux; Croatia

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