The Effects of Calcium and Nitrogen Amendments On Soil Organic Matter Dynamics In Pine Forests Stands At Sand Ridge State Forest.

Concern over the increase in atmospheric CO₂ content has created interest in the mechanisms that increase and stabilize organic matter in soils.  The present study examined the impacts of calcium and nitrogen on soil organic matter (SOM) in nutrient poor pine soils.  Literature supports that calcium increases soil C content and retention while the benefits of N additions on SOM retention are divided.  Increases in SOM resulting from additions of calcium and N to non agricultural soils would have potential to increase C sequestration in degraded systems.  Our study focused on low nutrient pine stands in the Sand Ridge State Forest in central Illinois.  Plantations were established at this site on native sand prairie in 1950’s.  Soil organic matter in these stands is generally low.  Amendments consisting of CaCl₂ and NH₄NO₃ were made in 2007.  Amendments were made separately and together on the surface of the soil and incorporated into the soil to 20 cm.  For the latter treatment litter was incorporated into soils with amendment mimicking tillage. Carbon mineralization incubations were initiated to examine the initial effects of each of these treatments.  There were significant differences detected in the amount of C released from soils even 500 days after treatment.  Calcium alone and with N had low rates of C evolution.  Calcium and Ca/N added with pine litter had higher C release than control but less than when litter was added without amendment or with N alone. Results suggest that Ca additions in forest soils decrease C loss through mineralization.  Whether this results in long term stabilization of soil organic matter; without affecting plant nutrient availability remains to be seen.  Forest plots will be evaluated for the next several years to determine the extent to which these trends continue and the impacts on above and belowground communities.