Bacterial feeder Nematodes: Facilitator or competitor for Plant Phosphorus in soil

Abstract

Rock phosphate is the main constituent of soil in lower Himalayan region of Pakistan but less accessible to plants. Although a lot of work has been done on the role of phosphate solubilizing bacteria for phosphorus availability from insoluble tricalcium phosphate (TCP), no significant success has yet been achieved at larger scale. The survival and function of introduced P solubilizing bacteria is directly influenced by their grazers present in soil. We hypothesized that the interactions between P solubilizing bacteria and grazer nematodes are able to improve P liberation from both TCP and bacterial biomass turnover. The hypothesis was tested by growing Pinus roxburghii seedlings in sand medium with or without TCP as a P source. The plants were grown alone or with a TCP solubilizing bacteria and bacterial-feeder nematodes. The test bacteria and the nematodes were isolated originally from pine rhizosphere of P mining zone located in lower Himalaya region of Pakistan. The grazing of bacteria by nematodes enhanced the P availability in the medium. Although bacteria were abundant in rhizosphere without nematodes they remained less efficient in P liberation compared to that measured in the presence of nematodes. Our data also showed that acidification was not the only reason of P availability from TCP. Another mechanism was prominent in liberation of the bacterial locked organic phosphorus via phospha-tase secretion as a result of nematodes predation. Our results, thus, open a new window towards the success and efficiency of bacterial-based biofertilizer, which mostly fail in the soil.