Crop Growth Parameters and their Measurements - Crop Growth Assessment and Modelling | Crop Production Notes- Agricultural Engineering PDF Download

Crop Parameter Values and User Inputs Table 8.2.1 presents parameter values for corn, soybeans, grain sorghum, cotton, winter wheat, spring wheat, oats, alfalfa, bromegrass, peanuts, tobacco, and annual ryegrass required by the cropland plant growth model. Values for corn, soybeans, and wheat parameters were obtained from the literature or estimated using measured field data. Several of the parameters were determined based upon long-term model simulations using climate input files for the major U.S. states producing those crops. Be sure to obtain the most recent version of the WEPP user documentation, as it will contain any updates to these parameters. Also, the Crop Parameter Intelligent Database System (CPIDS) (Deer-Ascough et al., 1993) was developed to assist users in developing WEPP plant growth parameters for crops not already parameterized. 

For cropland plant growth simulation, the user is generally required to provide the following information:

1. number of overland flow elements - (nelem) 

2. number of different crops in the simulation - (ncrop) 

3. cropping system (annual, perennial, or fallow) - (imngmt) 

4. crop types in the simulation - (itype) 

5. number of tillage sequences in the simulation - (nseq) 

6. number of tillage operations within each sequence - (ntil) 

7. Julian day of tillage (mdate), tillage depth (tildep), and tillage type (typtil) 

8. initial conditions at the start of simulation, including canopy cover (C_c), interrill residue cover (C_ri), rill residue cover (C_rr), and prior crop type (IRESD) 

9. crop information including planting date (JDPLT), row width (R_w), and harvesting date (JDHARV)
10. base harvest index which is used for partitioning live biomass into that removed as a harvested crop material (grain, silage, etc.) and that converted to dead crop residue. Default values for harvest index are provided in Table 8.2.1 for annual crops normally harvested as grain. These values may have to be increased if harvested for silage. 11. plant management information for annual crops including date of application of a contact herbicide (JDHERB) to convert living biomass to dead residue
12. plant management information for perennial crops that are cut, including the number of cuttings (NCUT), cutting dates (CUTDAY), and cutting height (CUTHGT)
13. plant management information for perennial crops that are grazed, including the date that grazing begins (GDAY), the date that grazing ends (GEND), the number of animal units (N_a), average body weight (B_w), field size (A_f), and the digestibility of the forage (D_g).

† A "-" indicates not applicable. Please check the current version of the WEPP User Summary document for updated values for these parameters.

* Three values of BEINP have been provided for most crops illustrated, representing the crops grown under Low/Medium/High fertility levels. 

** Growing degree days for crops to reach maturity varies by variety and region. Values listed here are typical for crop varieties grown near Indianapolis, Indiana. A value of 0 may be input to the model for any crop, and WEPP will internally compute a value for GDDMAX based upon the planting and harvest dates for an annual crop, and for the entire year for a perennial crop.

† A "-" indicates not applicable. Please check the current version of the WEPP User Summary document for updated values for these parameters. 

* Three values of BEINP have been provided for most crops illustrated, representing the crops grown under Low/Medium/High fertility levels. 

** Growing degree days for crops to reach maturity varies by variety and region. Values listed here are typical for crop varieties grown near Indianapolis, Indiana. A value of 0 should be input for GDDMAX for perennial crops which will be grown during the simulation, A value of 0 may be input to the model for any crop, and WEPP will internally compute a value for GDDMAX based upon the planting and harvest dates for an annual crop, and for the entire year for a perennial crop.