ISHS Acta Horticulturae 511: XXV International Horticultural Congress, Part 1: Culture Techniques with Special Emphasis on Environmental Implications - Nutrient Management
RELATIONSHIP BETWEEN TRUNK DIAMETER FLUCTUATIONS, STEM WATER POTENTIAL AND FRUIT GROWTH RATE IN POTTED ADULT APPLE TREES |
| Authors: | J. Bonany, F. Camps, J. Salvia, M. Cohen |
| Keywords: | Apple, diameter, fruit, growth, LVDT, potential, stem, transpiration, trunk, water |
| Abstract:
Methods available to schedule irrigation in decidous fruit crops are not completely satisfactory. Either water balance methods or soil based measurements have important disadvantages. Methods based on plant water status measurements are thought to overcome part of the problems and allow an irrigation management that would lead to enhanced fruit production and quality with more efficient water use and reduced tree vigour. One of the methods proposed to measure plant water status for irrigation scheduling is measurement of Trunk Diameter Fluctuations (TDF) using Linear Variable Differential Transducer (LVDT). Use of TDF derived parameters, Maximum Daily Shrinkage (MDS) and Daily Evolution (DE), have been proposed in different species as decision tools to manage irrigation. However, apple trees seem to behave differently from other tree species regarding the relationship between MDS and water stress compared to other fruit species. Additionally, threshold data for MDS and DE to be used to manage irrigation of apple commercial orchards is not widely available. Research was conducted to relate TDF with other plant water status measurements and fruit growth in order to use TDF for irrigation scheduling. On mature 'GOLDEN DELICIOUS' grafted on 'M9' planted in 100 L containers, TDF was monitored continously using LVDT connected to CR-10 dataloggers through several drought-irrigation cycles. LVDT's were also mounted on fruits to record fruit growth. Additionally, stem water potential was measured periodically throught the day. Relationships between TDF measurements and derived variable, MDS and stem water potential with fruit growth were analyzed and significance for irrigation scheduling discussed. A threshold value of 200 microns for MDS is proposed to irrigate apple trees. Above this value, fruit growth rate would start do decrease. This threshold needs to be validated under field conditions. | |
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