Model Library

Capabilities

• APEX is a robust, comprehensive field-scale model for simulating crop growth and environmental impacts (Texas A&M University, n.d.);
• APEX supports large, complex farming systems, including multiple fields, soils, rotations, and management practices (Texas A&M University, n.d.);
• APEX routes water, sediment, nutrients, and pesticides across landscapes and channel systems to the watershed outlet (Texas A&M University, n.d.);
• APEX evaluates global climate/CO2 effects, designs landfill and biomass systems, and supports diverse environmental applications (Texas A&M University, n.d.).

Limitations

• The tile drainage subroutine in APEX needs improvement (Guo et al., 2020);
• Simulation of flow and nutrient transport through macropores needs enhancement (Guo et al., 2020);
• APEX assumes phosphorus (P) as dissolved, not accounting for particulate P losses through tiles (Guo et al., 2020);
• APEX has limitations in accurately predicting flow, sediment, and nutrient losses due to process representation issues (Francesconi et al., 2014; Bhandari et al., 2017);
• APEX is not sensitive to soil bulk density differences in claypan landscapes (Mudgal et al., 2010);
• APEX does not support ponding conditions for paddy simulations (Kim et al., 2020).

Inputs

• Topography data, LULC data, Soil data, Meteorological data, Hydrological data, Water quality data, Management data, Socio-economic data.

Outputs

• The model simulates detailed water balance, sediment transport, and the fate of sediment, nutrients, carbon, and chemicals.
• It also models crop growth, soil water content, soil temperature, soil organic carbon pools, and net ecosystem exchange.

References

Osei, E., Jafri, S. H., Gassman, P. W., Saleh, A., & Gallego, O. (2023). Climate change impacts on surface runoff and nutrient and sediment losses in Buchanan County, Iowa. Agriculture, 13, 470. 
https://doi.org/10.3390/agriculture13020470

Guo, T., Confesor, R., Saleh, A., & King, K. (2020). Crop growth, hydrology, and water quality dynamics in agricultural fields across the Western Lake Erie Basin: Multi-site verification of the Nutrient Tracking Tool (NTT). Science of The Total Environment, 726, 138485. 
https://doi.org/10.1016/j.scitotenv.2020.138485

Objectives

The main objective of this study is to determine the extent to which projected changes in climate will impact edge-of-field surface runoff and associated sediment and nutrient losses from cultivated croplands.

The objective of the study was to develop a calibrated single parameter set Nutrient Tracking Tool (NTT) that can be used across fields in the Western Lake Erie Basin to simulate annual crop yields, water balance, and nutrient loads. The study aimed to ensure that simulation results are comparable with observed data, improve understanding of water balance and nutrient transport processes, and facilitate testing of conservation practices without site-specific monitoring data.