Does Stimulating Decomposers with Sodium and/or Carbon Increase Efficiency of Agricultural Phosphorus Cycling?.

Phosphorus (P) runoff from rural landscapes in Northwestern Ohio is one of the principal causes of harmful algal blooms in the Lake Erie Basin. Much of the P added to farm fields binds to soil particles and is relatively inaccessible to plants; thus, in a given year, typically more P is added to the fields than is taken up by plants. This excess P either leaches or accumulates in the soils over time, becoming “legacy P”, which can also enter waterways through erosion. Therefore, there is a critical need to reduce reliance on P fertilizers by enhancing biological P cycling and to find ways to increase the availability of bound legacy P. This work tests the hypothesis that by accelerating the rate of P release with C and/or Na, the amount of plant-available P in the soil will increase without additional fertilizer application—decreasing both P runoff potential and the amount of P that farmers need to apply.

We are working to find ways to increase the P cycling rates, thereby decreasing the amount of P fertilizer required. Specifically, we are testing the hypothesis that stimulating decomposers (such as bacteria and invertebrates) with a high carbon (C) substrate and/or sodium (Na) may increase the proportion of soil P available to plants. We predicted that small Na additions will increase invertebrate decomposer activity, and that additions of corn litter will increase microbial activity and P release from soil particles. To test these predictions, we set up 12 sets of plots in each of four conventionally-managed corn fields in northwestern Ohio to which we either added corn litter, a dilute sodium chloride solution, a combination of both, or neither. We then measured soil P, N and C concentrations, soil microbial enzyme activities, microbial respiration, and decomposer arthropod biomass.