Synergistic effect of releasing potassium bacteria and clay minerals improving maize growth and soil nutrients availability

Abstract: Widely distributed shallow-buried paleochannels sand-bodies are valuable reservoirs of shallow water resource in the coal mining area. It is located in the transition zone between Maowusu desert and Loess Plateau, in which ecological environment is fragile and vulnerable to damage. It is necessary to rationally develop and utilize soil in shallow-buried paleochannels for ecological restoration in the mining area of northwest china. In order to reveal the effects of releasing potassium bacteria on plant growth and soil nutrients utilization in the shallow-buried paleochannels in the Northwest Mining area, the study was performed by short-term pot cultures in heliogreenhouse with maize in artificial soils, which simulated the soils with different contents of clay minerals in paleochannels. Test artificial soils were composed of quartz and 2 kinds of potassium-rich clay minerals, including feldspar and illite which are common minerals in the soil of northwest mining area. The test artificial soils were treated with 6 levels of clay minerals, which followed by 18%, 25%, 38%, 45%, 68% and 75% mass fractions of clay minerals in soils. Each level of clay minerals treated with inoculation with active C6X or sterilized C6X. The C6X was the tested strains of releasing potassium bacteria Phyllobacterium ifriqiyense isolated from the garden soil in Beijing Suburbs by microbial reclamation laboratory in China University of Mining and Technology. We investigated the relationship between the releasing potassium bacteria quantity and the artificial soils with 6 different kinds of clay minerals ratios, and their synergistic effect on the growth of maize including dry weight of shoot, root shoot ratio and root activity, mineral nutrients of maize and apparent utilization ratios of nitrogen, phosphorus and potassium in soil. The results showed: 1) The quantity of releasing potassium bacteria was increased with increase in the clay minerals contents in soil. Releasing potassium bacteria quantity reached the peak value when the mass fraction of clay minerals in soil was 68% and concentration of exchangeable potassium in soil was 170 mg/kg, which was followed by decline of releasing potassium bacteria quantity at the mass fraction of clay minerals of 75%; 2) Maize dry weight of shoot, root shoot ratio, root activity were increased following the increase of clay minerals contents. When the mass fraction of clay minerals was 68% with inoculation with active C6X, the 3 indexes of maize growth reached maximum value; 3) The optimum mass fractions of clay minerals in soils with active C6X inoculation were 45%, 68% and 75% for accumulations of maize nitrogen, phosphorus and potassium and soil nutrients availability. The maximum apparent utilization ratios of soil potassium, nitrogen and phosphorus were 65%, 53% and 17%, respectively; 4) Releasing potassium bacteria promoted the absorption of phosphorus in the case of soil potassium deficiency (the mass fraction of clay minerals was 18%), while it promoted the absorption of nutrients in maize and use efficiency of nitrogen , phosphorus and potassium in the case that soil potassium exceeded (the mass fraction of clay minerals was 75%). The absorption and utilization of nitrogen, phosphorus and potassium in maize was closely associated with potassium content in the artificial soils, and was not significantly correlated with initial contents of nitrogen, phosphorus in the artificial soils. In sum, releasing potassium bacteria quantity was intensively influenced by the contents of clay minerals in soil. The interaction between clay minerals and releasing potassium bacteria in soil affected maize growth and nutrition uptake actively, also enhanced the utilization of mineral nutrients in soil. It provides useful information for exploring suitable microbial reclamation technology and improving degraded soil in mining area in northwest China.