Determination of Crop Water Stress Index for Pistachio Trees under Subsurface Drip Irrigation Using Canopy-Air Temperature Difference

Seifi, Akram; Mirlatifi, Seyed Majid; Dehghanisanij, Hossien; Torabi, Manouchehr

doi:10.22059/jwim.2014.51642

Determination of Crop Water Stress Index for Pistachio Trees under Subsurface Drip Irrigation Using Canopy-Air Temperature Difference

Document Type : Research Paper

Authors

Akram Seifi ¹

Seyed Majid Mirlatifi ²

Hossien Dehghanisanij ³

Manouchehr Torabi ⁴

¹ Ph.D Candidate, Department of Irrigation and Drainage Engergy, Tarbiat Modares University, Tehran, Iran

² Associate Professor, Department of Irrigation and Drainage Engergy, Tarbiat Modares University, Tehran, Iran

³ Assistant, Department of Irrigation Systems Research Department, Agricultural Engineering Research Institute, Karaj, Iran

⁴ Assistant, Department of Irrigation Systems Research Department, Agricultural Engineering Research Institute, Esfahan, Iran

10.22059/jwim.2014.51642

Abstract

This study was conducted to determine the possibility of a crop water stress index (CWSI) to schedule irrigation for Pistachio tree under subsurface drip irrigation. The effects of two irrigation intervals consisting 3 (I₃) and 14 (I₁₄) days based on measuring soil water content were investigated on the CWSI. From 22 May (DOY 143) to 22 September (DOY 266), the evapotranspiration in I₃and I₁₄ treatments varied from 795.45 to 490.79 mm, respectively. The CWSI was calculated using the empirical approach from measurements of infrared canopy temperatures, air temperatures and vapor pressure deficit values for the two irrigation levels. The lower baseline (non-water stressed baseline) was calculated as (T_c – T_a)_LL = -1.642 VPD + 1.432 with R² = 0.49. This equation had a correlation coefficient equal to 0.77 (P<0.01). An average threshold CWSI value of about 0.5 and 0.49 was calculated for I₃and I₁₄ treatments, respectively. Duncan test showed the effect of irrigation levels on CWSI was significant at P<0.05. Linear relationship between evapotranspiration and monthly CWSI calculated as ET = -804.7 CWSI + 680.1with determination coefficient equal to 0.6 (P<0.05). The CWSI can be employed as a useful tool for assessing crop water stress for Pistachio.

Keywords

canopy-air temperature difference

crop evapotranspiration

Infrared thermometer

Irrigation interval

Vapor pressure deficit