Leaf temperature of maize and crop water stress index with variable irrigation and nitrogen supply

Authors: CARROLL, DAVID - Brigham Young University; HANSEN, NEIL - Brigham Young University; HOPKINS, BRYAN - Brigham Young University; DeJonge, Kendall

Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2017
Publication Date: 9/19/2017
Citation: Carroll, D.A., Hansen, N.C., Hopkins, B.G., Dejonge, K.C. 2017. Leaf temperature of maize and crop water stress index with variable irrigation and nitrogen supply. Irrigation Science. doi:10.1007/s00271-017-0558-4.
DOI: https://doi.org/10.1007/s00271-017-0558-4

Interpretive Summary: Water stress indices based on crop canopy temperature can be useful for assessing plant water status and for irrigation scheduling, but an understanding of management practice interactions is needed. Irrigation timing and crop nutrient deficiencies could compound the interpretation of water status from leaf temperature by altering leaf color and radiation balance. The objective of this study is to evaluate three water stress indices derived from canopy temperature: Crop Water Stress Index (CWSI), Degrees Above Non-Stressed (DANS), and Degrees Above Canopy Threshold (DACT) in maize (Zea mays L.) under controlled deficit irrigation and varying supply of nitrogen (N). Replicated studies were conducted using maize grown in both glasshouse and field environments. The glasshouse study consisted of well-watered or drought irrigation and sufficient, intermediate, or deficient N levels. The field study consisted of well-watered, controlled deficit, or drought irrigation and sufficient, sufficient delayed, or deficient N levels. All three water stress indices were responsive to irrigation treatment, but did not account for differences in the timing of drought stress relative to critical crop growth stages. Nitrogen levels created widely different leaf chlorophyll concentrations but did not have a significant effect on leaf temperature or any of the water stress indices in the field. Correlations between CWSI and DACT indicated that a constant threshold temperature of 28.0 °C may be too high for some environments.

Technical Abstract: Water scarcity due to changing climate, population growth, and economic development is a major threat to the sustainability of irrigated agriculture in the Western United States and other regions around the world. Water stress indices based on crop canopy temperature can be useful for assessing plant water status and for irrigation scheduling, but an understanding of management practice interactions is needed. Irrigation timing and crop nutrient deficiencies could compound the interpretation of water status from leaf temperature by altering leaf color and radiation balance. The objective of this study is to evaluate three water stress indices derived from canopy temperature: Crop Water Stress Index (CWSI), Degrees Above Non-Stressed (DANS), and Degrees Above Canopy Threshold (DACT) in maize (Zea mays L.) under controlled deficit irrigation and varying supply of nitrogen (N). Replicated studies were conducted using maize grown in both glasshouse and field environments. The glasshouse study consisted of well-watered or drought irrigation and sufficient, intermediate, or deficient N levels. The field study consisted of well-watered, controlled deficit, or drought irrigation and sufficient, sufficient delayed, or deficient N levels. All three water stress indices were responsive to irrigation treatment. For example, average DANS values in the glasshouse were 3.25 °C for the drought treatment and 2.32 °C for the well-watered treatment and in the field were 4.65 °C, 5.45 °C, and 5.81 °C for the well-watered, drought, and controlled deficit irrigation treatments, respectively. These average values, however, do not account for differences in the timing of drought stress relative to critical crop growth stages. Nitrogen levels created widely different leaf chlorophyll concentrations but did not have a significant effect on leaf temperature or any of the water stress indices in the field. Measuring canopy temperature to assess water stress is robust across varying N levels, illustrating their usefulness in managing water applications even among variable field conditions. However, the water stress indices did not correlate well with leaf area due to the effects of N levels on plant growth. Compared to CWSI, DANS and DACT are simpler to calculate, similarly differentiated among irrigation levels, and were not affected by N treatment. Correlations between CWSI and DACT indicated that a constant threshold temperature of 28.0 °C may be too high for some environments. Water stress indices are useful tools in evaluating crop water status, but consideration of other factors, such as nutrient status, must be taken for prediction of crop growth and yield.