Formulations of arbuscular mycorrhizal fungi inoculum applied to soybean and corn plants under controlled and field conditions

Abstract

Phosphorus is one of the most important and limiting nutrient in plant development, as it is an exhaustible and non-renewable resource, but arbuscular mycorrhizal fungi (AMF) assist plants in uptaking nutrients from the soil, especially phosphorus, and can be used for artificial inoculation of seeds, enhancing their growth potential. The objective of this study was to evaluate the effect of three different substrates, peat (Pt), vermiculite (V) and rock phosphate (RP), as carriers for AMF inoculation (Rhizophagus clarus, produced in vitro), with and without P, in soybean (Glycine max L.) and corn (Zea mays L.). Experiments were carried out in a controlled environment (greenhouse) and at the experimental farm (field trial) of State University of Londrina, Brazil. The parameters evaluated were germination percentage, adhesion of infective propagules and carriers on seeds, AMF root colonization, shoot dry weight, grain yield and phosphorus (P) and nitrogen (N) content in leaves. The analyzed carriers generated different effects in the inoculated crops. In soybean, the AMF colonization was higher with vermiculite with added P, but an increase of 16.3% was detected in the yield when vermiculite was applied without P. The N content of soybean leaves was improved with rock phosphate, with and without P. In corn, peat with P increased the yield by 20%. The leaf N and P contents were higher when rock phosphate with P and vermiculite without P were used, respectively. Vermiculite produced negative effects in AMF colonization on corn, shoot dry weight, yield and seed germination. These results demonstrated that carrier substrates cause different effects in soybean and corn and hence the inoculum formulation needs to be specific for each plant.