RESPIRATION OF A SOIL USED FOR VEGETABLE CROPS AT THE BEGINNING OF THE VEGETATION PERIOD

Soil respiration was measured with a new portable soil respiration sys tem (PP Systems, Hitchin, England) in vegetable plots in the greenhous e and field near Bonn from January to May 1996 with the following resu lts: 1. The equipment proved suitable for the purpose over a wide rang e of temperatures. 2. Soil respiration ranged from less than 26 mg CO2 in winter, 30-180 mg CO2 in spring to 700 mg CO2 m(-2) h(-1) in summe r with large variations. 3. The largest soil respiration was recorded from peat-based commercial potting compost with small variations betwe en measurements. 4. The Q(10) was 2,5 (+/-0,6) in the field for temper atures between 5-25 degrees C. 5. The rate of soil respiration was aff ected by soil cultivation with the effect declining with temperature : Ploughing, which unveiled cold and produced a coarse soil surface;redu ced soil respiration, whereas soil respiration was increased by fine s oil cultivation. 6. In vegetable plots, soil respired 6-12 kg in cold (4 degrees C), 40-50 kg CO2 in cool (14 degrees C) conditions in April and 170-210 kg CO2/ha and 24 hours in warm (27 degrees C) weather.