UBC Theses and Dissertations
Impact of postharvest deficit irrigation and organic amendments on sweet cherry production at newly and previously established orchards in the Okanagan Valley Gebretsadikan, Tirhas Mebratu
In the Okanagan Valley, sweet cherry production has expanded to higher altitudes due to climate change, but water availability and maintenance of soil health are major concerns for sustainable production. This study examined the effects of mulches and postharvest deficit irrigation (PDI) on soil health, tree productivity and fruit yield and quality in cherry orchards over two seasons. Sweet cherry trees were planted with six replicates at three sites in a randomized block split-plot design, while a split-split-plot experimental design was used at the fourth site. Two irrigation rates (100% and ~70% water supply) were the main-plots, with mulches (compost, woodchips and bare ground) as sub-plots for three sites. Fumigation, compost and legacy effect of mulch and P fertigation were assigned accordingly as main-, sub- and sub-subplots at Site 4. Mulched (Sites 1-3) or incorporated (Site 4) compost increased soil organic matter, nutrients, pH and conductivity at all sites. Compost decreased arbuscular mycorrhizal fungi (AMF) colonization and increased total bacteria in soil, while fewer root P. penetrans were detected from incorporated compost alone or in combination with fumigation compared to the corresponding control. By contrast, woodchips affected only a few of these soil properties, including increasing soil C and C:N, and decreasing AMF colonization. The legacy effect of mulch at Site 4 was associated with increases in most soil nutrients, and higher total fungal populations when legacy mulch was combined with fumigation. Compost increased soil moisture compared to bare ground, but had no effect on stem water potential of cherry trees. Compost also increased leaf area, a few foliar nutrients and fruit quality attributes, while no impacts of woodchips were observed on these parameters compared to bare soil, with very few exceptions. Use of PDI saved up to 28% irrigation water after fruit harvest per season without affecting soil moisture, soil biochemical properties, stem water potential, or any tree growth and productivity parameters. Overall, results suggest that mulches are a promising strategy to maintain soil moisture, improve soil fertility, plant growth and productivity, and PDI has the potential to reduce irrigation water use after harvest without affecting cherry production.
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Attribution-NonCommercial-NoDerivatives 4.0 International