Horticultural Additives influence soil biogeochemistry and increase CO2 emissions from peat

<p>Peat is used as the chief ingredient of growing media in horticulture. The high cation exchange capacity, water retention capacity, low bulk density, and appropriate physical properties make peat-based growing media desirable for horticulture. Peat in its natural form is acidic and low in nutrient composition. Therefore, for suitability as a growing media, peat is mixed with liming agents, nutrients, surfactants, perlite among several other possible additives.</p><p>Using lab incubations, we assessed the change in soil biogeochemistry and CO2 fluxes because of horticultural additives. We obtained samples of raw peat and additive mixed growing media (n=52) from four different peat extraction companies in Canada. Our analysis shows that the key soil biogeochemical parameters C: N ratio, pH, dissolved organic carbon, bulk density, C content differs significantly (p<0.01) between raw peat and growing media. There is a more than a two-fold increase in CO₂ from growing media as compared to raw peat. Further experiment showed the longer-term contribution of carbonates borne CO₂ to the total flux.&#160;</p><p>IPCC (2007) calculates that all C from harvested peat is lost in the atmosphere in the first year. However, our initial results estimate less than 10% of peat C loss in the first year from growing media. Although the influence of horticultural additives in C loss from peat is significant, the current accounting from IPCC is an overestimation.</p>