# Corn

## Water Production Function

New Mexico Crop Information Corn Water Production function or the relationship between Evapotranspiration and yield

Et = evapotranspiration or water used by crop.

The water production function has grain yield expressed in kg/ha at 15.5 % moisture content.

The reference for this work is Kallsen, C. E. , E. J. Gregory and T. W. Sammis. 1983. Water Use Production Functions of Selected Agronomic Crops in Northwestern New Mexico, Phase III WRRI Report No 159 New Mexico State University.

If you have any questions please contact webmaster@weather.nmsu.edu Updated: Dec 18 1996 Copyright © 1996 New Mexico State University Department of Agronomy and Horticulture Box 30001 / Dept.3Q / Las Cruces, N M 88003-8003 Telephone: (505)646-3405 FAX: (505)646-6041

## Crop Coefficients

New Mexico Crop Information Corn coefficient(k) to calculate evapotranspiration(ET) where Et=k*Eto

Eto = reference evapotranspiration or potential evapotranspiration referenced to grass.

Crop Coefficient uses growing degree days (GDD) accumulated from planting based on the averaging method of calculating GDD with a maximum temperature cutoff of 30 C and a minimum cutoff temperature of 10 C. The Base Temperature is 10 C.

The equation for the crop coefficient (k) is: k=1.20E-1 +1.68E-3 Gdd -2.46E-7 GDD^2-4.37E-10 GDD^3 with an R^2=0.83 based on data from Clovis and Farmington NM. The crop coefficient equation is appropriate for a furrow irrigated crop with corn yield around 9000-12000 kg/ha To convert from GDD to Date get the accumulative heat units for the current year from the weather convert page. Use the metric format because the GDD days are metric units. To convert GDD in degree C to GDD in degree F multiply the value by 1.8.

The reference for this work is Sammis T. W. , C. L. Mapel, D. G. Lugg, R. R. Lansford , J. T. Mc Guckin 1985. Evapotranspiration Crop Coefficients Predicted Using Growing Degree Days ASAE 28(3):773-780

If you have any questions please contact webmaster@weather.nmsu.edu Updated: Dec 18 1996 Copyright © 1996 New Mexico State University Department of Agronomy and Horticulture Box 30001 / Dept.3Q / Las Cruces, N M 88003-8003 Telephone: (505)646-3405 FAX: (505)646-6041

## Irrigation Schedule

New Mexico Irrigation scheduling for corn

Climate data should be copied from web site using Netscape. If you use Explorer, copy climate data to Notepad and then copy from Notepad to spreadsheet. Click on part of picture for instructions on how to fill out spreadsheet. A copy of the spreadsheet has been developed that uses Samani's equation for potential evapotranspiration requiring only temperature data.