Model and Production Function for Irrigation Management

Abstract

A simulation model was developed to estimate the effect of deficit irrigation upon crop yield. The model was designed to provide relative yield estimates for numerous combinations of irrigation system, crop growth and irrigation management parameters. A daily soil moisture balance was used to predict evaporation and transpiration from which crop yields were estimated. Gross irrigation water requirements were estimated from net irrigation requirements, irrigation efficiencies, irrigation system limitations, and effective rainfall. Crop production functions that use physically defined parameters were also developed to relate crop yields to gross irrigation requirements. The production functions worked well on a limited test compared to field data. The model and production functions are general since they depend upon readily available information or physical parameters, and can be used to evaluate irrigation management alternatives.

Crop Yield and Water Requirement Relationships for Major Irrigated Crops in Southern Alberta

“…Stewart et al (1977) and Doorenbos and Kassam (1979) predicted relative yield reductions from the product of relative evapotranspiration deficits and a crop-specific yield response factor or yield reduction ratio. This approach has been used extensively to estimate relative yield from inadequate irrigation applications or shortages in water supply (Martin et al, 1984;Scheierling et al, 1997;Kirda et al, 1999;Raes et al, 2006;Shrestha et al, 2010). Relationships between crop yield and evapotranspiration may subsequently be used to develop crop water production functions that relate crop yield to the field water supply, which includes effective precipitation, stored soil moisture depletion, and irrigation amounts that account for spray droplet evaporation and water drift outside the target area, surface runoff, and deep percolation losses (Stewart and Hagan, 1973;Vaux and Pruitt, 1983;Howell, 1990).…”

Evaluation of Irrigation Planning Decisions

“…Martin et al (1984) developed a method to estimate the necessary coefficients for commonly used production functions. The technique is based upon a linear relationship of yield to evapotranspiration (ET):…”

“…Generally, these coefficients are determined from regression analysis of data from a specific experiment. Using the three conditions previously listed, Martin et al (1984) developed relationships between physical parameters and these coefficients for a quadratic, exponential, and power function used to describe the yield response ratio. Martin et al showed that using the physically based coefficients in the production functions represented experimental data as well as regression analysis results for data from Nebraska.…”

“…The definition of β emerges from the analysis of Martin et al (1984). The parameter β represents the portion of the irrigation that is used by the crop as evapotranspiration when producing the maximum yield.…”

“…A simulation program (Martin et al, 1984) was used to calculate the parameters for the crop production function. The model was used to simulate the evapo- …”