Impact of some Plant Growth Promoting microorganisms and Humic Acid on Phosphorus Solubilization for increasing Murcott tangerine Production

Abstract

Egyptian lands generally suffer from a deficiency of phosphorus because a large part of the phosphorus nutrient is fixed in the soil in the form of tricalcium phosphate (TCP) due to high temperatures and lack of organic matter with an increase in pH. Two field experiments were conducted at in a private orchard (Pico Farm) located in Giza governorate, Egypt during two seasons (2021-2022) to study the influence of plant growth promoting microorganisms (PGPM) and humic acid on phosphate solubilization of Murcott tangerine trees (Citrus sinensis (L.) Osbeck x Citrus reticulata Blanco) with winter management and/or after fruit set compared to control a randomized complete block design. All tested microorganisms were apparently able to trigger PGPM properties. However, Trichoderma asperellum appeared to be superior in IAA, P-solubilization Bacillus megatherium recorded the best production of exopolysaccarides. As for the nature of siderophores, two strains exhibited hydroxymate nature whereas, carboxylate nature was showen by Trichoderma. on the contrary of catecholate nature which was not produced by either strains. The obtained results showed a significant rise in all measured parameters for yield efficiency, fruit set percentage, leafy inflorescence's percentage, fruit quality attributes, biochemical contents and mineral content of leaves as compared with the control. Optimum results were obtained from the T7 (Humic acid with winter management + after fruit set) and T4 (PGPM with winter management + after fruit set) treatments.