Articles
Climatic and canopy factors influencing transpiration of young and full-bearing pomegranate orchards under semi-arid conditions
Article number
1464_35
Pages
259 – 266
Language
English
Abstract
Quantifying tree transpiration and relating it to canopy characteristics and climatic processes is important knowledge that can be applied to improve irrigation management practices.
The pomegranate production industry depends on rainwater harvesting during the winter to ensure enough water reserves during the growing season (summer). Currently, there is no adequate information in South Africa on the influence of canopy-related variables on transpiration and how the climate influences the transpiration of pomegranate trees.
This study investigates the influence of canopy characteristics and daily weather parameters on the daily transpiration of pomegranate trees, as well as the role of climatic factors in driving transpiration at an hourly scale.
The study was conducted in the Western Cape Province of South Africa on commercial farms in the Porterville and Drakenstein districts.
Transpiration was measured using the heat ratio method.
The fractional interception and leaf area index (LAI) were measured using a ceptometer.
Weather data was recorded using an automatic weather station.
Sap flow measurements were conducted for six months (November to April) during the 2023/2024 growing season for eight trees that varied in stem diameter.
The fractional interception related better with transpiration than LAI. The correlation analysis between the diurnal sap flow, net radiation, air temperature and wind speed showed a strong positive relationship with a p-value <0.0001; however, a negative relationship was observed with the relative humidity.
The air temperature was the most important variable responsible for over 70% of the variation in transpiration for the young orchard, and the net radiation contributed to 86.5% of the variation for the full-bearing orchard.
Based on the stepwise regression, it can be concluded that the air temperature and the net radiation are the main drivers of hourly transpiration for the young and full-bearing orchards, respectively.
The pomegranate production industry depends on rainwater harvesting during the winter to ensure enough water reserves during the growing season (summer). Currently, there is no adequate information in South Africa on the influence of canopy-related variables on transpiration and how the climate influences the transpiration of pomegranate trees.
This study investigates the influence of canopy characteristics and daily weather parameters on the daily transpiration of pomegranate trees, as well as the role of climatic factors in driving transpiration at an hourly scale.
The study was conducted in the Western Cape Province of South Africa on commercial farms in the Porterville and Drakenstein districts.
Transpiration was measured using the heat ratio method.
The fractional interception and leaf area index (LAI) were measured using a ceptometer.
Weather data was recorded using an automatic weather station.
Sap flow measurements were conducted for six months (November to April) during the 2023/2024 growing season for eight trees that varied in stem diameter.
The fractional interception related better with transpiration than LAI. The correlation analysis between the diurnal sap flow, net radiation, air temperature and wind speed showed a strong positive relationship with a p-value <0.0001; however, a negative relationship was observed with the relative humidity.
The air temperature was the most important variable responsible for over 70% of the variation in transpiration for the young orchard, and the net radiation contributed to 86.5% of the variation for the full-bearing orchard.
Based on the stepwise regression, it can be concluded that the air temperature and the net radiation are the main drivers of hourly transpiration for the young and full-bearing orchards, respectively.
Authors
M. Ravuluma, P.C. Tharaga, T. Volschenk, S. Dzikiti, S. Walker
Keywords
daily transpiration, leaf area index, fractional interception
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