Articles
SAP FLOW MEASUREMENTS TO ASSESS REGULATED DEFICIT IRRIGATION STRATEGIES ON CITRUS TREES
Article number
951_7
Pages
71 – 78
Language
English
Abstract
Transpiration of well watered (C) and regulated deficit irrigated (RDI) trees was determined by means of the compensation heat pulse method during 2009 and 2010 in commercial citrus groves of Clementina de Nules (CN) and Navel Lane Late (NLL). In both species, sap flow (SF) was measured in two trees per treatment instrumented with two gauges per tree.
CN trees were equipped with two different types of gauges (type1 shorter than type2) determining heat velocity from crossing time at four different xylem depths according to Green et al. (2003). In NLL oranges, all the gauges were identical and the data were processed according to the compensation heat pulse + calibrated average gradient (CAG) method (Testi and Villalobos, 2009). Plant water status was determined by midday stem water potential measurements (Ψstem). Results showed that the absolute SF values, and especially those from type2 gauges in CN, clearly underestimated tree water use.
Tree to tree variability registered in CN (CV=0.09) was lower than in NLL (CV=0.17) which also showed a 17% of within tree variability.
The average nocturnal-to-diurnal sap flow ratio was between 7% and 13%. The evolution of relative SF (e.g.
SFRDI/SFC) was in agreement with differences in Ψstem (r2=0.78 in CN and 0.84 in NLL). This SF ratio showed the expected decreasing trend during the water restriction period and the recovery when irrigation was reestablished to normal dose.
Overall, the results show that sap flow sensors can detect plant water stress but they also highlight some of the problems for accurately measuring transpiration.
CN trees were equipped with two different types of gauges (type1 shorter than type2) determining heat velocity from crossing time at four different xylem depths according to Green et al. (2003). In NLL oranges, all the gauges were identical and the data were processed according to the compensation heat pulse + calibrated average gradient (CAG) method (Testi and Villalobos, 2009). Plant water status was determined by midday stem water potential measurements (Ψstem). Results showed that the absolute SF values, and especially those from type2 gauges in CN, clearly underestimated tree water use.
Tree to tree variability registered in CN (CV=0.09) was lower than in NLL (CV=0.17) which also showed a 17% of within tree variability.
The average nocturnal-to-diurnal sap flow ratio was between 7% and 13%. The evolution of relative SF (e.g.
SFRDI/SFC) was in agreement with differences in Ψstem (r2=0.78 in CN and 0.84 in NLL). This SF ratio showed the expected decreasing trend during the water restriction period and the recovery when irrigation was reestablished to normal dose.
Overall, the results show that sap flow sensors can detect plant water stress but they also highlight some of the problems for accurately measuring transpiration.
Publication
Authors
C. Ballester, J. Castel, D.S. Intrigliolo, J.R. Castel, L. Testi
Keywords
compensation heat pulse method, transpiration ratio, water stress
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