Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2016
Publication Date: 10/11/2016
Citation: Gitz, D.C., Baker, J.T., Lascano, R.J. 2016. Scaling leaf measurements to estimate cotton canopy gas exchange. American Journal of Plant Sciences. 7:1952-1963.

Interpretive Summary: Crops require vast amounts of water, but water suitable to irrigate crops is becoming more and more limited. To insure that water is available for future crop production and to meet the ARS grand challenge of increasing crop production with less water, irrigation timing and amount must be optimized. To develop new irrigation schemes we need to be able to both measure the amount of water used by a crop and measure crop performance. Here we showed that we can infer the amount of water being used by a cotton crop can be estimated by measuring a single leaf. While it is generally held that this cannot be done our results indicate that it is possible, at least in an arid environment in a well-watered cotton plant. This is also important because it shows that agronomists might be able to develop irrigation crop coefficients for semi-arid environments without resorting to much more costly approaches.

Technical Abstract: Diurnal leaf and canopy gas exchange of well watered field grown cotton were measured. Leaf measurements were made with a portable photosynthesis system and canopy measurements with open Canopy Evapo-Transpiration and Assimilation (CETA) systems. Leaf level measurements were arithmetically scaled to estimate canopy level gas exchange and the modeled canopy level gas exchange compared to that of the measured. Canopy transpiration was well predicted, although both transpiration and assimilation were overestimated around mid-day. We concluded that canopy cotton transpiration of well watered field grown plants in a semiarid environment can be closely (within 5%) estimated throughout the day by scaling leaf level measurements to canopy leaf area. Estimating canopy assimilation from leaf measurements remains problematic.