Agricultural fields in Northwest Ohio and the Maumee River watershed are frequently tile-drained and fertilized with phosphate to optimize plant growth. Phosphate is often lost from fields via surface runoff and tile drainage, either with particulate soil matter or as dissolved reactive phosphate. Soil health can influence the retention and loss of phosphate. Stable oxygen isotopes may provide a non-invasive way of measuring the biological turnover rate of phosphate in soils over longer time scales than previous methods. To validate the ability of oxygen isotopes in phosphate to measure biological turnover, three fields in the Maumee River watershed in Northwest Ohio were sampled from Fall 2016-Summer 2017. Samples were collected before, during, and after fall tilling and fertilization, and before and after spring planting and fertilization. Each sampling included samples before, during, and after rain events.
Results/Conclusions
Preliminary results suggest that dissolved reactive phosphate in soil water increases after fertilization and rainfall, across a period of 2 months, suggesting potential for the use of this approach to assess biological turnover of phosphate in agricultural field. Measuring the rate of biological turnover of phosphate in soil could help researchers and field managers better understand the mechanisms behind the effects of various best management practices (BMPs) on nutrient runoff.