Estimating Crop Water Production Functions Based on Transpiration and Crop Growth Curves through Modeling

This report concerns the development of crop growth curves based upon growing degree days instead of calendar days and the development of crop water production functions based upon transpiration.

Lysimeter data to carry out these procedures for alfalfa, corn, wheat, barley, grain sorghum and cotton was available from four New Mexico sites with different climates. Once the crop growth curves were derived, they were statistically compared to determine if they were similar in spite of the climatological differences. Results indicate that the crop growth curves were statistically (P>0.05) similar for crops grown from northern to southern New Mexico.

Lysimeter data was not available for lettuce, onions, chile, potatoes or pinto beans. Thus, crop coefficients were derived from the literature and a modeling approach was utilized to devise the crop growth curves based upon growing degree days.

The development of crop water production functions based upon transpiration also was carried out for the above crops. This step was undertaken to remove some of the variability caused by the evaporation component of evapotranspiration. These functions can be used statewide and on various soil types.