Soil Nutrient Dynamics and Yield in a Young Merlot Grape (Vitis vinifera) Vineyard: Implications of Irrigation and Soil Amendment Practices.

Soil nutrient dynamics and yield in a young Merlot grape (Vitis vinifera) vineyard: implications of irrigation and soil amendment practices

K.D. Hannam¹, G.H. Neilsen², D. Neilsen², T. Forge², M.D. Jones¹, C. Nichol³ and M. Fentabil³

¹Biology Department, University of British Columbia Okanagan, Kelowna, B.C V1V 1V7 Phone: 250-494-2101 Email:kirsten.hannam@agr.gc.ca

²Agriculture & Agri-food Canada, Pacific Agri-Food Research Centre

Summerland, B.C. V0H 1Z0

³Earth and Environmental Sciences, University of British Columbia Okanagan, Kelowna, B.C V1V 1V7

In the Okanagan Valley of British Columbia, there is growing interest in the use of management practices that reduce water consumption, improve resource use efficiency, and enhance soil organic matter.  In 2011, a Merlot grape (Vitis vinifera) vineyard was established to compare the effects of irrigation using drip emitters or microsprinklers on nutrient availability, fruit quality and yield.  Nested within the irrigation treatments, five soil amendment treatments were applied that use various combinations of compost, mulch and fertigation to deliver 40 kg available nitrogen/ha/yr.  Ion-exchange resins were used to monitor soil inorganic N levels through the 2013 growing season.  Soil moisture and temperature were measured using time domain reflectometry probes and thermocouples, respectively.  Petioles were sampled at bloom and at veraison for analysis of tissue nutrients; fruit yield and juice composition were measured at harvest.  Drip irrigation increased soil nitrate, particularly later in the growing season; this pattern appears to be related to treatment differences in the distribution of irrigation water.  Petiole N concentrations were also higher under drip irrigation, but there was no effect of irrigation treatment on fruit yield.  Soil nitrate was decreased under the mulch treatments but this could not be explained by the soil microclimate or soil carbon variables that were measured.  Application of N via fertigation with urea increased petiole N at bloom relative to application of N via compost but this effect had disappeared by veraison, and there were no effects of soil amendment on fruit juice composition or yield at harvest.  The results of this study suggest that considerable savings in water and chemical fertilizers could be made through the use of soil amendments, such as compost or surface mulch, with few - if any - negative consequences for the yield or composition of wine grapes.