Effect of Bio-Organic Amendments on Growth, Yield, Nodulation Status, and Microbial Activity in the Rhizosphere Soil of Peanut Plants under Sandy Soil Conditions

In a field experiment, plant growth, nodulation status, yield, mineral content, and the rhizosphere enzyme activities of peanut (Arachis hypogaea L), cultivated in sandy loam soil were studied under the effect of the amendment with humic acid and the inoculation with plant growth promoting rhizobacteria (PGPR) that applied as foliar andor as seed coating. Bradyrhizobium was used as a single inoculum andor accompanied with PGPR (Azospirillum sp.+ Paeniacillus polymyxa+ Serratia marcescens) with or without humic acid. Results revealed that inoculation with Bradyrhizobium as a single inoculum or accompanied with PGPR, increased significantly shoot dry weight, and yield of peanut under coating and foliar applications.  Incorporation of humic acid at two rates of 3L/fed and 5L/fed as foliar and seed coating gave the highest significant values for all tested parameters.  inoculation with Bradyrhizobium as single inoculum or accompanied with PGPR enhanced the nodulation status and nitrogenase activity.  Also, the values of nodules and nitrogenase activity achieved by coating application method were higher than those recorded by foliar application. In addition, the combined application of coinoculation Bradyrhizobium and PGPR accompanied with humic acid led to significant increases in the content of N, P, and K in shoot plant and in soil. Likewise, humic acid amendment can stimulate the microbial activities in the rhizosphere soil. Higher values of dehydrogenase activity in the rhizosphere soil and carbon dioxide were found with coinoculation and foliar application of humic acid.