Nutrient Retention of Artificial Soils Used in the Eden Project Biomes (Cornwall, UK).

The Eden Project (EP), in Cornwall, prepares its own artificial soils for use on site by recycling waste materials sourced from throughout the region; components include sand, lignite clay, composted green-waste and bark, with approximately 83,000 tonnes deployed to date. Inconsistent management practices have resulted in variable soil performance, with respect to plant growth. This study focuses on the biogeochemistry of EP soil, with the ultimate aim of improving nutrient retention and storage potential within these soils, and artificial soils more generally.

The nutrient retention characteristics of the artificial soil were investigated. Soil was packed into 4 columns (1 m x 0.11 m height x diameter) which were subjected to the EP irrigation regime (6x5 minute waterings/24 hours, delivering 0.14 mL cm^-2 18.2 MΩ cm^-2 water). Column leachate was monitored for nutrient concentrations in the leachate for 12 months. The leached total dissolved nitrogen concentrations changed declined over the first 180 days, from  13.1 - 2.51 mg L^-1, pH decreased during this period, from 6.7 to 6.5. From day 15 nitrate+nitrite concentration represented <5% of the total dissolved N present within the leachate, implying that there was a significant fraction of dissolved organic nitrogen (>95%). The decrease in pH may have resulted from the gradual release of organic acids. Additional measurements will be made to confirm this.

 The high nitrogen concentrations present within the leachate suggest that there is potential for a nitrogen recycling process, helping to lower operational costs for EP.