Sap Flow Monitoring to Improve Water and Nutrient Management Strategies for Sweet Cherry (Prunus avium L.).

Sap flow monitoring to improve water and nutrient management strategies for sweet cherry (Prunus avium L.)

Gerry Neilsen¹ and Denise Neilsen¹, ¹Research Scientists, Pacific Agricultural Research Centre, Agriculture and Agri-Food Canada, Summerland, BC, Canada VOH 1Z0. Phone: 250-494-6377 Email:Gerry.Neilsen@agr.gc.ca

         In semi-arid, irrigated, production regions of western North America, climate change and variability pose threats to consistent production of high value, perennial fruit crops which must withstand changing multi-year temperature and moisture regimes and increasingly unreliable water supply for irrigation. Continuous sap flow measurements have been advocated as a technique to refine irrigation strategies for woody perennials. Little information is available for sweet cherry which has increasingly been planted in the Pacific Northwest. Thus a series of greenhouse and field experiments were undertaken to examine the possible use of sap flow as a stress indicator for cherry. In the greenhouse, Granier style thermal dissipation probes (TDP) were installed in replicated two-year old Van/Mazzard sweet cherry trees subjected to two different irrigation frequencies prior to re-watering to field capacity. Strong correlations were observed between transpiration measured by weight loss of sealed plots and sap flow which also responded to rewetting. TDP probes were subsequently installed in mature sweet cherry trees in two randomized, replicated field experiments. For ‘Lapins'/Gisela 5, sap flow was monitored in response to soil moisture dry down in trees irrigated daily via drip at 100% ET prior to imposition of  50 % and 25% ET deficit irrigation treatments one week prior to harvest. Sap flow responded to decreased water supply but did not consistently predict tree water use suggesting limitations to this method for determining total water use. In a commercial orchard, sap flow measurements on ‘Sweetheart'/Mazzard trees indicated minimal flow until bloom, reduced flow in trees receiving nutrient sprays and instances where diurnal sap flow did not correlate to temperature implying soil moisture limitations to transpiration. These findings have implications for cherry nutrient and water management.