Soil moisture sensor calibration, actual evapotranspiration, and crop coefficients for drip irrigated greenhouse chile peppers

• Published in: Agricultural water management 2017-01, Vol.179, p.81-91
• Main Authors: Sharma, Harmandeep, Shukla, Manoj K., Bosland, Paul W., Steiner, Robert
• Format: Article
• Language: English
• Subjects: Chile peppers; Compartments; Crop coefficient; Crops; Deep percolation; Evapotranspiration; Greenhouse; Greenhouses; Hydra; Irrigation; Peppers; Roots; Seasons; Sensors
• ISSN: 0378-3774; 1873-2283
• DOI: 10.1016/j.agwat.2016.07.001

•Year round chile pepper production in greenhouse has water and nutrient saving potential.•New calibration equations were developed for three soil moisture sensors.•No significant differences in transpiration rate and leaf temperature were observed when less irrigation water applied.•Irrigation scheduling can be done using sensors and/or crop coefficients. Limited water supplies in arid regions put constraints on agriculture. In arid New Mexico, greenhouse chile pepper production has the potential for water and nutrient savings. The objectives of this study were to (1) compare two capacitance sensors – (Hydra probes and 5TM) and one TDR CS616 sensor, (2) compute actual evapotranspiration (ETa) for drip-irrigated chile peppers for three water treatments, and (3) develop new crop coefficients (Kc) for the three growing seasons in a greenhouse study. Three water treatments were (1) control where water was applied near the surface using two drip emitters, (2) partial root zone drying vertical (PRDv) where subsurface irrigation was applied at 20cm depth from soil surface, and (3) partial root zone drying compartment (PRDc) where roots were divided into two compartments and irrigation were switched between compartments after 15days. Sensor-generated volumetric water contents (θ) were correlated with the gravimetrically determined θ, and the new calibration coefficients improved the precision of θ estimates. From 2011 onward, irrigation amounts were adjusted to minimize deep percolation, and about 30% less water was applied in 2014 as compared to the 2011 growing season but no significant differences were observed in transpiration rate and leaf temperature. The ratio of intercellular to ambient CO2 concentrations (Ci/Ca) was significantly correlated to transpiration rate and vapor pressure deficit in 2014 (P