ARRANGEMENT OF EXPERIMENTS FOR SIMULATING THE EFFECTS OF ELEVATED-TEMPERATURES AND ELEVATED CO2 LEVELS ON FIELD-SOWN CROPS IN FINLAND

The experimental plants: spring wheat, winter wheat, spring barley, me adow fescue, potato, strawberry and black currant were sown or planted directly in the field, part of which was covered by an automatically controlled greenhouse to elevate the temperature by 3 degrees C. The t emperature of the other part of the field (open field) was not elevate d, but the field was covered with the same plastic film as the greenho use to achieve radiation and rainfall conditions comparable to those i n the greenhouse. To elevate the CO2 concentrations, four open top cha mbers (OTC) were built for the greenhouse, and four for the open field . Two of these, both in the greenhouse and in the open field, were sup plied with pure CO2 to elevate their CO2 level to 700 ppm. The tempera tures inside the greenhouse followed accurately the desired level. The relative humidity was somewhat higher in the greenhouse and in the OT C:s than in the open field, especially after the modifications in the ventilation of the greenhouse and in the OTC:s in 1994. Because the OT C:s were large (3 m in diameter), the temperatures inside them differe d very little from the surrounding air temperature. The short-term var iation in the CO2 concentrations in the OTC:s with elevated CO2 was, h owever, quite high. The control of the CO2 concentrations improved eac h year from 1992 to 1994, as the CO2 supplying system was modified. Th e effects of the experimental conditions on plant growth and phenology are discussed.