بررسي وضعيت تنش آبي درختان زيتون با استفاده از شاخص تنش آبي گياه

Investigation of Water Stress Status of Olive Trees Using Crop Water Stress Index

ﻫﺪف از اﯾﻦ ﻣﻄﺎﻟﻌﻪ ارزﯾﺎﺑﯽ ﻗﺎﺑﻠﯿﺖ ﺷﺎﺧﺺ ﺗﻨﺶ آﺑﯽ ﮔﯿﺎه )Crop Water Stress Index, CWSI( ﺣﺎﺻﻞ از اﻧﺪازهﮔﯿﺮي دﻣﺎي ﭘﻮﺷﺶ ﮔﯿﺎﻫﯽ درﺧﺘﺎن زﯾﺘﻮن ﺑﺎ اﺳﺘﻔﺎده از دﻣﺎﺳﻨﺞ ﻣﺎدون ﻗﺮﻣﺰ، در ﺑﺮرﺳﯽ وﺿﻌﯿﺖ ﺗﻨﺶ آﺑﯽ و ﺑﺮﻧﺎﻣﻪرﯾﺰي آﺑﯿﺎري درﺧﺖ زﯾﺘﻮن ﺑﻮد. ﺑﺮاي اﯾﻦ ﻣﻨﻈﻮر راﺑﻄﻪ ﻣﯿﺎن ﺷﺎﺧﺺ ﺗﻨﺶ آﺑﯽ ﮔﯿﺎه و ﺷﺎﺧﺺﻫﺎي ﻣﺤﺘﻮاي ﻧﺴﺒﯽ آب ﺑﺮگ )Relative Water Content, RWC( و رﻃﻮﺑﺖ ﺧﺎك )Soil Water Content, SWC( ﺗﻌﯿﯿﻦ ﺷﺪ. ﺗﯿﻤﺎرﻫﺎي آزﻣﺎﯾﺸﯽ ﺷﺎﻣﻞ دو رﻗﻢ زﯾﺘﻮن ﮐﺮوﻧﯿﮑﯽ و T2( و ﭼﻬﺎر رژﯾﻢ آﺑﯿﺎري )آﺑﯿﺎري ﺑﺮاي ﺗﺄﻣﯿﻦ 70 ،85 ،100 و 55 درﺻﺪ از ﻧﯿﺎز آﺑﯽ ﮔﯿﺎه( ﺑﻮد. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ راﺑﻄﻪي ﺧﻂ ﻣﺒﻨﺎي ﺑﺪون ﺗﻨﺶ در ﻃﻮل دورهي ﭘﮋوﻫﺶ و ﻫﻤﭽﻨﯿﻦ در ﻃﻮل روز ﻣﺘﻐﯿﺮ ﺑﻮد. ﺗﻐﯿﯿﺮات روزاﻧﻪ ﺧﻂ ﻣﺒﻨﺎي ﺑﺪون ﺗﻨﺶ درﺧﺘﺎن زﯾﺘﻮن ﻋﻤﺪﺗﺎً ﺑﻪدﻟﯿﻞ ﺗﻐﯿﯿﺮ در ﻋﺮض از ﻣﺒﺪأ ﺧﻂ ﻣﺒﻨﺎي ﺑﺪون ﺗﻨﺶ ﺑﻮد ﮐﻪ ﺑﻮﺳﯿﻠﻪي ﺗﻐﯿﯿﺮات زاوﯾﻪي رأس ﺧﻮرﺷﯿﺪ ﻗﺎﺑﻞ ﺗﻮﺻﯿﻒ اﺳﺖ. ﭘﺲ از ﺑﺮرﺳﯽ ارﺗﺒﺎط ﻣﯿﺎن ﮐﻤﺒﻮد ﻓﺸﺎر ﺑﺨﺎر آب در اﺗﻤﺴﻔﺮ ) Vapor Pressure Deficit, VPD( و اﺧﺘﻼف دﻣﺎي ﭘﻮﺷﺶ ﮔﯿﺎﻫﯽ و دﻣﺎي ﻫﻮا )Tc − T𝑎(، راﺑﻄﻪي T -Ta=1.06-0.45 VPD, r2=0.99 ﺑﺮاي ﺧﻂ ﻣﺒﻨﺎي ﺑﺪون ﺗﻨﺶ درﺧﺘﺎن زﯾﺘﻮن در ﺳﺎﻋﺖ 12:30 ﺑﻌﺪ از ﻇﻬﺮ ﺗﻌﯿﯿﻦ ﺷﺪ. ﺷﺎﺧﺺ ﺗﻨﺶ آﺑﯽ ﮔﯿﺎه درﺧﺘﺎن زﯾﺘﻮن در رژﯾﻢﻫﺎي ﮐﻢآﺑﯿﺎري ﻧﺴﺒﺖ ﺑﻪ ﺷﺮاﯾﻂ آﺑﯿﺎري ﮐﺎﻣﻞ ﺑﻪﺻﻮرت ﻣﻌﻨﯽدار، اﻓﺰاﯾﺶ ﯾﺎﻓﺖ. ﺷﺎﺧﺺ ﺗﻨﺶ آﺑﯽ ﮔﯿﺎه ﺑﺎ ﺷﺎﺧﺺﻫﺎي ﻣﺤﺘﻮاي ﻧﺴﺒﯽ آب ﺑﺮگ )ﮐﺮوﻧﯿﮑﯽ:**r2=0/82 و r2=0/80** :T2( و درﺻﺪ ﺟﺮﻣﯽ رﻃﻮﺑﺖ ﺧﺎك )ﮐﺮوﻧﯿﮑﯽ:**r2=0/66 و T2: **r2=0/69( ﻫﻤﺒﺴﺘﮕﯽ ﻣﻌﻨﯽدار داﺷﺖ. ﺑﻨﺎﺑﺮاﯾﻦ، ﺷﺎﺧﺺ ﺗﻨﺶ آﺑﯽ ﮔﯿﺎه، ﺷﺎﺧﺺ ﻣﻨﺎﺳﺒﯽ از وﺿﻌﯿﺖ ﺗﻨﺶ آﺑﯽ درﺧﺘﺎن زيتون ﮐﺮوﻧﯿﮑﯽ و T2 اﺳﺖ.

The aim of this study was to assess the crop water stress index (CWSI), derived from leaf temperature using infrared thermometer measurements, to investigate the water stress status and irrigation timing of olive trees. Fpr this purpose a regression function was determined between crop water stress index and relative water content of leaf (RWC) and soil water content (SWC). The experimental treatments involved two olive cultivars (Koroneiki and T2) and four water regimes (irrigation of 100, 85, 70 and 55% of crop water requirement). The results showed that the non-water stressed baseline is varied throughout the study period as well as during the day. The daily variations of non-water stressed baseline were mainly due to variations in the intercept of the non-water stressed baseline that can be explained by variations in zenith solar angle. After investigating the relationship between vapor pressure deficit (VPD) and the difference between crop and air temperature (), the equation of Tc-Ta = -0.45 VPD+1.06, r2 = 0.99 was determined for the non-water stressed baseline of the olive trees at 12:30 pm. The effect of irrigation regime on water stress index of Kroneiki and olive trees was not significant in none of the measurements during the study period. However, crop water stress index was significantly correlated with relative water content (Kroneiki: r2=0.67**, : r2=0.88**) and soil water content (Kroneiki: r2=0.74**, : r2=0.78**). Therefore, the crop water stress index is a good indicator of the water stress status of the Koroneiki and T2 olive trees.