Influence of beneficial microbes and proline treatments on sugar beet under nitrogen limitation in saline-sodic soil

A field experiment on sugar beet [Beta vulgaris L.] yield and yield quality under saline-sodic soil conditions was conducted at Sahl El Hussinia Res. Station, El Sharkia Governorate, Egypt, during the winter season of 2008/2009. The influence of cyanobacteria and N[2]-fixing bacteria were compared either individually or in combination to supplementation with proline amino acid under two levels of mineral nitrogen fertilization [50 and 75% of nitrogen recommended dose]. Soil enzymatic activities [dehydrogenase and nitrogenase], total bacterial counts, total cyanobacteria counts and total nitrogen fixing bacteria counts were enhanced by the biofertilizers compared to proline treatment and controls, particularly when the combined inoculum of cyanobacteria and N[2]-fixing bacteria was applied in the presence of 75% N. In addition, inoculation with cyanobacteria and N[2]-fixing bacteria, either individually or in combination with 75%N, led to a slight decrease of pH and EC values of saline soil, while there was an increase in the availability of NPK as compared with control plots. Proline and biofertilizers showed a significant positive impact on some physiological properties of plants drown at 75% nitrogen level, such as chlorophyll in leaves, proline and phenolic compounds in roots. The highest responses for these traits were in proline-treated plots followed by the combined inoculation of cyanobacteria and N[2] fixing bacteria, while, there was no significant difference in root yield productivity between proline treatment and the combined inoculum of cyanobacteria and N[2] fixing bacteria with 75% nitrogen fertilizer. The combined inoculation positively increased N, P and K uptake and decreased the uptake of Na in roots. Also, the combined inoculum of cyanobacteria and N[2] fixing bacteria with 75% nitrogen led to a significant increase in shoot and root dry weight as well as root yield quality [sucrose and purity]. Results suggest that the beneficial effect of the cyanobacteria and N[2] fixing bacteria on sugar beet growth, yield and yield quality was attributed to the biologically active substances produced by these microbial strains besides the nitrogen fixation of the diazotrophs which compensate the reduction of the costly and the environmentally polluted mineral nitrogen fertilizers in the new reclaimed saline-sodic soil

Evaluation of the potential of two plant growth promoting rhizobacteria [PGPR] on the increase of wheat productivity under different salinity regimes

A POT experiments was conducted winter 2007-2008 at the experimental greenhouse of Microbiology Department, Soils, Water and Environment Research Inst., ARC, Giza, Egypt, to evaluate the response of the wheat cultivars, Sakha 93 and Gemiza 7, to be inoculated with Azotobacter sp. and Bacillus sp., under two salinity regimes [NaCl concentration 100 mM and 150 mM, respectively] for improving salinity tolerance in sandy soils. The results showed that dehydrogenase and nitrogenase activities were significantly inhibited by increasing salinity in the rhizosphere of all uninoculated plants. The chlorophyll-a [chl. a], chlorophyll-b [chl. b] and carotenoid contents of 30 days old seedlings were significantly reduced in response to increase of salinity levels in all treatments. Data also revealed that increasing salinity level caused an increased gradual accumulation of proline in the shoots of the stressed wheat plant in both cultivars. Bacterial amendment resulted in a significant increase in all measured yield parameters compared with the un-amended control. The mineral contents [N, P and K] in both wheat cultivars varied as a response to the saliniy regims and presence of Azotobacter sp. and Bacillus sp., N, P and K contents of grains were significantly decreased with increasing salinity in all treatments in both cultivars but most pronounced in Gemiza 7