November 1, 2013

Intermittent water stress and severe drought can limit corn yields in the Corn Belt and in many other parts of the world where corn is grown under rainfed conditions. Producers, crop consultants, crop insurance providers, and policy makers need robust tools to estimate and quantify the impacts of water stress and drought on crop yield and to devise strategies for mitigation. Crop simulation models provide a powerful tool for these purposes.

The new release (Version 2013.4) of the Hybrid-Maize model, developed by researchers in the UNL Department of Agronomy and Horticulture, incorporates several new components to improve performance in simulating yields under moderate to severe water stress based on data from recent research. Compared to the previous release (version 2006.3), the new version offers the following improvements and new features:

1. More responsive and robust functions to account for the impacts of water stress on leaf area expansion and senescence (Figure 1).
2. Improved simulation of soil water balance by:
   — simulation of surface runoff based on field slope, soil drainage class, and soil surface residue coverage (Figure 2);
   — simulation of soil moisture at planting time by tracking soil water balance during the pre-planting fallow period (Figure 3); and
   — revised simulation of soil surface evaporation and influence of crop residues cover on that evaporation rate
3. Improved simulation of kernel setting under water stress conditions.
4. Improved simulation of rooting depth and lateral root distribution.
5. The option of using alfalfa- or grass-referenced evapotranspiration (ET) in weather data
6. The option of running a large number of simulations with one click by using input settings in an Excel spreadsheet.
7. Fully compatible with Windows 7 and earlier Windows operating systems.
8. Upgraded weather data utility program, “WeatherAid,” which is fully compatible with Windows 7 and earlier Windows operation systems.

Figure 1 (left). New version vs old version on simulated leaf area index (LAI) under water stress.

Figure 2 (right). User input settings for estimation of surface run-off based on residue coverage and field slope and drainage.

Figure 3 (below left). User input settings for estimating soil moisture status at planting by tracking soil water balance in the pre-planting fallow period.

Figure 4 (below right). Simulated vs. measured corn yield under rainfed conditions in the US Corn Belt based on yield data from rainfed maize fields that received near optimal management. 

Overall, the new version offers a more user-friendly interface, greater functionality, and more importantly, produces more robust simulation results under water stress conditions (Figure 4).

Hybrid-Maize modeling software can be purchased online from the NUtech Ventures for $35.

Dr. Haishun Yang, Associate Professor
Dr. Patricio Grassini, Assistant Professor
Dr. Ken Cassman, Professor
UNL Department of Agronomy and Horticulture