Smart irrigation for sweet corn : evapotranspiration-based or soil moisture sensor-based scheduling technique?

Abstract

Globally, water deficit during the growing season is a major factor limiting sweet corn and overall crop production. Irrigation scheduling is one of the novel methods that can be used to achieve ideal crop yield while saving water. The overall goal of this study was to compare between two smart irrigation scheduling methods, the ET-based and soil moisture sensor-based systems under different treatments and their effects on sweet corn morphometric parameters in improving water productivity while observing sap flow rates in different soil moisture regimes. The two experiments were carried out at the Agricultural Research and Educational Center (AREC) of the American University of Beirut (AUB) in Lebanon’s Beqaa Valley. The ET-based experiment had three treatments calculated to be equal to 60percent, 90percent, and 120percent of Penman-Monteith (ETC), and was automatically set and calculated via an irrigation controller. The soil moisture sensor-based irrigation experiment had SM25percent, SM30percent, and SM35percent which were thresholds recorded from soil moisture sensors whereby an irrigation event was initiated when soil volumetric water content (SVWC) reached the soil water depletion thresholds. All the irrigation treatments had three replicates and had flow meters installed on all six irrigation treatments to measure the applied irrigation water. Results showed a positive linear relationship between fresh ear yield and amount of water applied, regardless of the scheduling method, increasing at the rate of 32kgm⁻³. More so, water saving was realized in irrigation treatments ET60percent, SM25percent and ET90percent at 29percent, 11percent, and 5percent respectively. Deficit irrigation in both scheduling methods showed an increase in water productivity except in ET60percent, which had a significantly low yield of 11.92 tha⁻¹. High soil moisture conditions proved as detrimental on yield as water stress conditions in the productivity of sweet corn. Sap flow data had a positive relationship with ET and the amount of applied water. Only treatment SM30percent had a hig