Response of maize plants to inoculation with azospirilla and (or) straw amendment in Egypt

Abstract

A pot experiment was designed to investigate the effects of inoculation with Azospirillum and (or) straw amendment on growth of plants grown in Giza soils. Inoculation caused increases in plant dry weight (200%) and total N content (157%) of plants. These characters were correlated with increases in ATP production in rhizosphere (492%), nitrogenase activity (438%), and densities of Azospirillum sp. (116-fold). Addition of straw only (5%, w/w) to the soil stimulated rhizosphere microorganisms (ATP, 410%), N2 fixation (nitrogenase activity, 392%), and also plant growth (plant dry weight, 176%; total N content, 149%). Simultaneous Azospirillum inoculation and straw amendment exerted the most favourable conditions for N2 fixation on roots (nitrogenase activity, 554% increase over control) leading to the greatest biological (numbers of azospirilla, 156-fold; ATP, 543%; nitrogenase activity 554%), as well as agronomic (total dry weight, 343%; total N content, 196%; leaf surface, 478%) effects. Under farming conditions of Egypt, field-grown plants benefitted from inoculation with Azospirillum sp. Increases up to 150–170%, 180–270%, and 120–130% were reported for straw yield, grain yield, and total N, respectively. Three cultivars responded differently to inoculation, and application of 200 kg N Ha−1 significantly reduced nitrogenase activity.