BIOFERTILIZERS AS COMPLEMENTS TO SYNTHETIC AND ORGANIC FERTILIZATION - Fertilizers: Components, Uses in Agriculture and Environmental Impacts - page 170

and P uptake by 27.5%. According to the authors the increase in these variables was the result
of a more developed root system, which permitted to expand the exploratory capacity of the
plant in the soil.
Naveed et al. (2008) demonstrated the possibility of maintaining grain maize yields by
replacing 87 Kg urea ha -1 (50%) of the complete N fertilizer dose (175 Kg ha -1 ) with 300 Kg
ha -1 of an organic compost elaborated with fruit and vegetable wastes and enriched with 147 g
N fertilizer Kg -1 compost; a basal dose of P and K (100 and 50 Kg ha -1 , respectively) was
applied to all field plots. However, when the N-enriched compost was inoculated with
different strains of Pseudomonas and then applied to the field plots conjunctly with 88 Kg
urea ha -1 a significantly increase (1.1 ton grain ha -1 ) in the growth and yield of maize was
observed over full dose of N-fertilizer and exhibited superiority over organic fertilizer (0.5
ton grain ha -1 ). According to the authors, Pseudomonas fluorescens strain N3 was particularly
effective in promoting growth because of its high capacity of root colonization, chitinase
activity and ACC deaminase activity, characteristics that confer this strain a relatively more
competitive advantage. Effects of rhizobacteria containing ACC deaminase activity are well
known for improving root growth of plants as a result of reduced ethylene synthesis through
ACC hydrolysis into NH 3 and α-ketobutyrate in the inoculated roots (Shaharoona et al. ,
2007). These results imply that inoculation of organic fertilizers with PGPR possessing these
traits could help developing improved biological products combining the nutritional
characteristics of the compost and the beneficial activities of the rhizobacteria with
synergistic effects on growth and productivity of crops.
Khurram et al. (2012) evaluated the effect of Bacillus strains possessing ACC deaminase
activity and phosphate solubilizing characteristics, either as a single mechanism or a dual
mechanism (strains with both features). Under axenic conditions, the bacterial strains with
dual plant growth-promoting activities were superior in improving growth of wheat as
compared to the strains possessing single trait. Similarly, these dual traits bacterial strains
were more effective than single trait strains under soil conditions (pot trial) in increasing root
weight (up to 3.9-fold) and root elongation (up to 3.8-fold), dry shoot weight (up to 37.6%),
number of tillers (up to 56%), grain yield (up to 38.5%) and P uptake in grain (up to 77.4%)
of wheat grown in the presence of P applied as diammonium phosphate (DAP), RP (rock
phosphate) or RP-enriched compost. An almost similar trend was observed when the same
trial was repeated under field conditions. Inoculation in the presence of RP-enriched compost
resulted in promoting various growth parameters almost comparable to that recorded in the
case of DAP. It was concluded that the simultaneous presence of two superior plant growth-
promoting traits in the bacteria could have an additive effect not only on growth and yield of
wheat but also on P uptake. The performance of Bacillus strains possessing dual traits was
distinctly superior to that of the single trait strains.
Abdullahi et al. (2013) studied the effect of using a biofertilizer (containing Azospirillum
sp. and Glomus mosseae ) and poultry manure (PM) on nutrient uptake, plant growth and soil
microbial population associated with sesame under field conditions. Plant height, numbers of
leaves/plant, numbers of branches/plant, leaf area, shoots and root dry biomass increased
significantly due to the application of the biofertilizer and poultry manure singly or in
combination over control. Combined application of the biofertilizer and poultry manure at 5
ton/ha (bio-organic treatment) significantly produced the plants with the best growth
parameters, nutrient content, and N, P, and K uptakes, and also recorded the highest
populations of Azospirillum sp. (28.56 X 10 -6 CFU g -1 soil) and AM fungi (69.3 AM spores g -