DETERMINATION AND ASSESSMENT OF SOIL TEMP ERATURE-DEPENDENT CHANGES IN INORGANIC N-CONTENTS AND STUDIES INTO N-DYNAMICS OVER THE GROWING-SEASON

A total of 91 field trials were made, determining at fourtnight interv als the inorganic N contents (inorganic N/mineral N) in the 0-30-cm la yer. Simultaneously, soil temperatures were recorded at a depth of 20 cm. N uptake rates were studied in eight field trials at three differe nt locations. With the help of linear estimation functions changes in soil inorganic N were calculated for the period between 10 March and e nd of June. The results were r = 0.654** in sand/loamy sand and r = 0 .585** in loam/loamy loess. In the mean of ten years, N mineralizatio n in soil under fallow was 35 and 40 kg.ha-1, respectively. Annual dev iations were between 10 and 15 kg.ha-1. Proceeding from the N uptake r ate of winter cereals and the soil inorganic N/mineral N content at di fferent periods of the growing season, N mineralization until maturity totals 100 kg.ha-1.