Sap flow measurements and cotton irrigation

Authors: Lascano, Robert; VAN BAVEL, MICHAEL - Dynamax Inc; Baker, Jeffrey

Submitted to: International Workshop on Sap Flow
Publication Type: Abstract Only
Publication Acceptance Date: 10/7/2019
Publication Date: 10/7/2019
Citation: Lascano, R.J., Van Bavel, M.J., Baker, J.T. 2019. Sap flow measurements and cotton irrigation. International Workshop on Sap Flow. Presentation. Helsinki, Finland, October 5-11, 2019.

Interpretive Summary: The stem heat balance method using sap flow sensors is a direct measure of crop transpiration. Scientists from the ARS in Lubbock, working with a commercial company tested the sensor with cotton plants in a greenhouse experiment and with cotton plants using growth chambers in a field experiment. The cotton water use in the greenhouse was measured by weighing potted plants and in the growth chambers was measured by gas exchange, measured with an infrared gas analyzer. Our results showed that for a wide range of conditions the sensors correctly measured the water use of the cotton plants. This sensor is one of a kind that can be used for a variety of tests that require the direct hourly and daily measurement of cotton plants.

Technical Abstract: The stem heat balance (SHB) method to measure plant transpiration (T) and using stem flow gauges has been extensively tested in a variety of agricultural plants with emphasis on horticultural crops. These include grapes, olive trees and other wood plants; however, its application to agronomic crops such as cotton has been somewhat limited. Recently, a new design of a stem gauge based on the SHB was introduced and the measurement of cotton-T was evaluated and tested in greenhouse and field experiments. In the greenhouse, values of cotton-T obtained with the stem gauge were compared to values off cotton-T measured gravimetrically on potted plants. In the field experiment, cotton-T measured with the stem gauges were compared to values measured with portable growth chambers, where the vapor flux (cotton-T) was measured using infrared gas analyzers. Results from these comparisons indicated a close relation, i.e., linear regression analysis, between the values of cotton-T measured with the new design of the stem gauges and values of cotton-T measured in the greenhouse and field experiment. Our next step is to evaluate how the measurements of cotton-T obtained with the gauges can be used to schedule the seasonal irrigation of a cotton crop. We further examine our experimental field data of measured cotton-T relative to reference evapotranspiration (ETo) and the calculation of crop (Kc) and stress coefficients (Ks) to derive actual values of cotton evapotranspiration.