The Relationship Between Soil Water Potential, Environmental Factors, and Plant Moisture Status for Poblano Pepper Grown Using Tensiometer-Scheduled Irrigation

Managing irrigation using soil moisture sensors for automation can allow for a reduction in water use while avoiding drought stress and maintaining optimum yields in high-value crops. Measurements of plant water status such as leaf water potential and relative water content are often utilized to demonstrate the presence or lack of drought stress in plants subjected to varying soil moisture regimes. Poblano peppers (Capsicum annuum L.) were grown under four automated, tensiometer-controlled irrigation regimes with set points of on/off -30/-25, -40/-35, -50/-45, and -60/-55 kPa and a manually operated treatment with set points of -50/-10 kPa. Soil moisture data were collected at depths of 15 and 25 cm and plant midday leaf water potential and relative water content data were collected throughout the growing season. Yield and fruit quality were unaffected by irrigation treatment. Soil water potential was poorly correlated with plant leaf water potential and relative water content. Plant leaf water potential and relative water content were well correlated with the following environmental factors: air temperature, relative humidity, dew point temperature, and solar radiation. These data indicate that in a non-drought-stressed production system leaf water potential and relative water content may be poor indicators of soil water status because they may be affected by environmental variables to a greater extent than by soil moisture.