Reactive Transport Modeling of the Combined Effects of Elevated Ambient Temperatures and Drought on Fertilizers of Cultivated Soils

Abstract:

Climate change and its accompanying temperature will impact agro-ecoystems across the globe. More frequent drought is expected to accompany elevated temperatures in many agro-intensive regions of the United States. The combined effect of drought and increased temperatures can reduce crops’ ability to assimilate carbon and can disrupt reproductive development, leading to reduced yield and quality. Such climate disturbances can have an enormous impact on global economics and food supplies.

This project aims to determine if changes in ambient temperature and soil moisture negatively impact the availability and movement of K⁺ and SO₄^-2-bearing nutrients within soil systems by modeling their reactive transport. Four major simulations will be conducted to determine the stand-alone effects of elevated temperature (10 °C above ambient) and drought (rainfall and cessation of irrigation), as well as a range of combinations of drought and elevated temperature. Highly versatile, non-isothermic and multiphase modeling codes like TOUGHREACT enable the design and development of 1D model simulations that provide insight on the solubility and precipitation kinetics of soil nutrients when subjected to elevated temperature and drought. The models will be parameterized with real-time soil moisture, temperature, and electrical conductivity data, as well as diurnal atmospheric temperature and pressure data from experimentally heated soybean plots. These data will also serve to validate the reactive transport simulations. Additionally, soil texture and chemistry will be modeled from 80cm soil profiles, irrigation-water chemistry acquired from previous regional groundwater analyses, and nutrient loadings quantified from the amounts applied in the experimental plots.

We hypothesize that the combined effect of drought and elevated ambient temperatures will lead to an increase in the range and depth of the soil dehydration profile, effectively limiting fertilizer movement across soils. Certainly, diminished nutrient mobility can have cascading effects on crop productivity and soil sustainability, such as limiting the depth at which nutrients are available for plant uptake. If this hypothesis is supported, an additional pathway by which climate change impacts agro-ecosystems will be defined.