| Abstract: | Effect of different fertilizers on the potential N2-fixing capacity (acetylene-reduction assay) of a sandy orthic luvisol The N2-fixation capacity of 36 different soil samples, taken from a field trial with 4 fields crops, was tested by the acetylene-reduction-method. Each of the 4 plots was divided into strips. I = mineral fertilizer (NPK), II = stable manure compost, III = stable manure compost with bio-dynamic preparations. These different kinds of fertilizer were given in three amounts of N: 1 = 0,5 × A kg N/ha, 2 = 1 × A kg N/ha, 3 = 1,5 × A kg N/ha. Like the 3 years before in 1984 rye ?Halo”? A = 100, potatoes ?Nicola”? A = 120, red beets ?Rote Kugel”? A = 160, carrots ?Luwal”? A = 120 were cultivated. The soil samples were taken after harvest, dried and sieved. 50 g soil were moistened with a glucose-solution, hatched at 25°C for 24 h and then incubated for another 24 h at the same temperature and an acetylene concentration of 9,23%. The amount of ethylene which had developed after 8 h, 15 h and 24 h was analysed by GC. The acetylene-reduction (AR) of the soils was significantly higher after the cultivation of rye and potatoes compared with carrots and red beets; but always the crops formed the main influence. On an average the organic manured soils showed a higher AR than the mineral fertilized ones. The encouraging effect of the different organic manures was depending on the type of crop. |
