CO2 emissions from cultivated peat soil with sand addition, a CAOS project

Peatlands store a major share of the world’s soil organic carbon and are widespread in Northern and Central European countries. Drainage is a precondition for classical agricultural production on organic soils. Drainage fosters peat mineralization and changes the physical and chemical soil quality. Only few decades after initial drainage, agricultural systems on drained organic soils start experiencing a high risk of crop failure. Decreased hydraulic conductivities lead to decreased infiltration, ponding, and finally to abandonment as drainage will not be effective anymore. One of the problems of (wet) organic soils is the low trafficability. The aim in this experiment is to investigate if the addition of foundry sand to the top soil will improve the trafficability without increasing the CO2 emission. In the Swedish part of the CAOS project, a field experiment (Randomized block design, 3x3) was set up at a former cultivated, but now abandoned, fen peat located at Bälinge Mossar (60.02821N, 17.43008E). We will compare trafficability, yield and CO2 emission from plots sown with Phleum pretense and treated with 0 cm, 2.5 cm or 5 cm foundry sand. The sand was applied in the autumn of 2015 and mixed in the top 10 cm of the soil. Penetration resistance, yield and CO2 emissions will be compared during three years. The first preliminary results (15/9-1/11) show that the CO2 emissions is highest from the plots without sand addition (3.4 µmol*m-2s-1) and lowest from the plots where 5 cm sand was added (1.4 µmol*m-2s-1). The emission from the 2.5 cm treatment was 1.8 µmol*m-2s-1. Yield and trafficability have not been measured yet, but it is promising that the CO2 emission from the plots with sand addition was much lower than untreated soils.