A pot experiment was carried with biofertilizers of N2-fixers (A. chroococcum+A.brasilense), P-dissolvers (Bacillus megaterium) and K-dissolvers ((Bacillus circulans) for sorghum (Sorghum bicolor) grown on a light clay torrifluvent soil. Different combinations of such N1, P1 and K1 biofertilizers were compared with the N0P0K0 non-addition which gave 15.2 g pot-1. All additions giving one or more or all of the 3 biofertilizers caused positive response. Ranges of % increase were: 63 (N1P0K0) to 81(N1P1K0) for yield; 63 (N0P0K1) to140 (N1P1K0) for N uptake; 88 (N1P0K1) to 224 (N1P1K1) for P uptake and 69 (N0P1K0) to 130 (N0P0K1) for K uptake. When given singly (solely), the percentage increase caused by any of the 3 biofertilizers was higher than when given in presence of any or both of the others (i.e. interaction effects). For yield, increases of 63, 67 and 65 % occurred due to a sole application of N, P and K biofertilizers respectively. Main (average) increases were 13, 14 and 12 % for each biofertilizer respectively (irrespective of presence or absence of the others).The average increase by one was greater in absence of each of the others, and generally non effective in presence of the other. Similar patterns occurred regarding uptake of N, P and K. The interactions among the 3 biofertilizers were evident. An indication of competition among the micro-organisms could have taken place. Practical implications indicate that biofertilizers could be used to decrease total dependence on chemical fertilizers. |
