Free air CO2 enrichment of potato (Solanum tuberosum, L.): design and performance of the CO2-fumigation system

Free Air CO2 Enrichment (FACE) systems are used to fumigate unconfined field plots with CO2. As these installations can treat a sufficiently large area without interfering with natural climatic conditions, they are considered important tools for global change research worldwide. However, there is general consensus that elevated capital costs of existing FACE systems as well as high running costs may prevent their application at the required level of scale. A new and small FACE system that was designed to reduce both capital costs and CO2 use, is described in this paper. Due to its intermediate size (8 m diameter) between the smaller Mini-FACE systems that were developed in Italy and the larger systems designed by the Brookhaven National Laboratory in the USA, it was named Mid-FACE. The Mid-FACE was at first developed as a prototype and then used to enrich field grown potato crops in a CO2 concentration gradient experimental design. Technical details of a Mid-FACE prototype and of the operational set-up are presented in this paper together with performance data in terms of temporal and spatial control of CO2 concentrations within the experimental area.