NTT general calibration and validation process

The Nutrient Tracking Tool (NTT) uses the Agricultural Policy Extender (APEX) model to estimate nutrient and sediment losses as well as crop yields. APEX uses a combination of site specific data (crop management information, weather, soil and slope) and regionalized environmental parameters to estimate the results produced in NTT program. Simulations are usually done for >30 years and the main function of NTT to evaluate and compare different farm-management practices in order to minimize nutrient and sediment losses while economically optimize the crop production. However, in order to ensure that parameters used in APEX for the regional NTT simulation are appropriate the following tasks within each stage are taken:

Stage 1.     To obtain a general parameterization for each state/region, a series of NTT runs simulating common crop rotations, soils and, weather patterns for the region is done and the results are compared with expected crop yield and nutrient and sediment loss values obtained from National Agriculture Statistics Service, USDA (NASS 2017) .

Stage 2.     During this stage, the field-scale measured data from various sources (e.g., local measured studies and collaborators) are used to finalize the regional APEX parameters.

Stage 3.     The final parameters obtained from stage 2 will be used to repeat the process described in stage 1. However, the various conservation practices, common to the local region, are also simulated and evaluated for all soils and weather conditions during this stage.

Stage 4.     The final results are evaluated and presented to local stakeholders (if any) and collaborators. The results of the parameterization (for all stages) would be available on the NTT site.

STATE: Indiana

Below are the results for Indiana statewide simulations of APEX using the parameters derived through a regional parameterization method (Stage 1). We display the average nutrient, sediment and water quantity results over all simulations.

Stage: 1

Type of parameterization: Regional only (no field-scale data available at this time)

Number of counties: ALL (92)

Number of Soils: 853

Slope: 0-10%

Tile drain depth (for poorly drained soils only): 3.28 ft. (1 m)

Simulation Period: 1981-2015

Number of Scenarios: 16

Scenarios:

Table 1: Crop management scenarios

 *refer to table 2; ** wheat as cover crop

Table 2. Fertilizer Application

Summary of Results:

The results below are averaged over the 35 years simulation period.

A.   Crop Yield:

Table 3. Average crop yield for all crop management scenarios

*National Agriculture Statistics Service, USDA

B.   Water Quantity:

B.1. Tile System

Table 4. Annual average hydrologic components for each crop rotation

Table 5. Annual average hydrologic components for all crop management scenarios

*Range

B.2. No Tile System

Table 6. Annual average hydrologic components for each crop rotation

Table 7. Annual average hydrologic components for all crop management scenarios

*Range

C.   Water Quality:

C.1. Tile System

Table 8. Annual average nutrient and sediment loads for all crop management scenarios

*Range

Table 9. Annual average nutrient and sediment loads for each crop rotation

Table 10. Nutrient and sediment loads from commercial fertilizer application

 Table 11. Nutrient and sediment loads from manure application

C.2. No Tile System

Table 12. Annual average nutrient and sediment loads for all crop management scenarios

*Range

Table 13. Annual average nutrient and sediment loads for each crop rotation

Table 14. Nutrient and sediment loads from commercial fertilizer application

 Table 15. Nutrient and sediment loads from manure application