Effect of Claroideoglomus etunicatum, vermicompost and phosphate sources on root colonization and growth of lettuce

Phosphorus is one of the important macro nutrients. Available phosphorus in calcareous soils is low, due to high pH and calcium carbonate, and low amounts of organic matters and moisture, also phosphate minerals are insoluble in such conditions. Arbuscular mycorrhiza inoculation for improving plant growth and yield has become so attractive recently. The symbiosis between plant roots and arbuscular mycorrhizal fungi with increasing phosphorus uptake (through phosphorus uptake by extra and intraradical mycelia and also solubilizing inorganic and organic insoluble phosphates), other nutrients and water cause increase in plant growth. Vermicompost increases the growth of plants due to having nutrients, plant growth regulators and beneficial microorganisms. This research was conducted to evaluate the effect of arbuscular mycorrhizal fungi, vermicompost and phosphate sources on root colonization, shoot fresh and dry weights, number of leaves, chlorophyll index and phosphorus uptake of lettuce in a calcareous soil.
A greenhouse experiments was conducted with factorial arrangement in a completely randomized design with three factors and replications in a calcareous soil. Treatments consisted of two levels of arbuscular mycorrhiza (Claroideoglomus etunicatum (AM)) (with and without inoculation), two levels of vermicompost (0 and 1% w/w) and four phosphate sources (control (P0), rock phosphate (RP), tricalcium phosphate (TCP) and triple super phosphate (SP) at 25 mg P kg-1 level). Non sterile soil was used and its characteristics along with vermicompost were analyzed by standard methods. Seeds of lettuce (Lactuca sativa) cv. Ferdos were planted. After 10 weeks after planting, chlorophyll contents, leaves numbers, fresh and dry weights, root colonization and phosphorus uptake were measured. Data were analyzed with SAS statistical software.
Application of vermicompost increased root colonization and phosphate sources decreased it. The highest rate of root colonization was observed in co-application treatments of vermicompost and arbuscular fungus and in the absence of phosphate sources. Mycorrhizal inoculation increased shoot dry weight and phosphorus uptake. Vermicompost application increased shoot fresh and dry weights, number of leaves, chlorophyll index and phosphorus uptake. Application of SP increased shoot fresh and dry weights and decreased chlorophyll index and phosphorus uptake. Application of RP decreased chlorophyll index and increased shoot dry weight and phosphorus uptake. Co-application of mycorrhizal fungi, vermicompost and phosphate sources increased shoot fresh and dry weights, number of leaves and phosphorus uptake.
Application of biofertilizers (vermicompost and arbuscular fungi) along with insoluble phosphate source (RP and TCP) can be increased phosphorus uptake and plant growth and reduced the consumption of chemical fertilizers especially SP.