Seasonal changes in leaf nutrient concentration of male and female hardy kiwifruit grown in Oregon

摘要

Leaf nutrient concentration of hardy kiwifruit [Actinidia arguta var. arguta (Siebold and Zucc.) Planch. ex Miq.] was evaluated throughout two growing seasons (2008-2009) for determinate and indeterminate shoots of female ('Ananasnaya') and male vines. While research has been conducted on the more commonly grown fuzzy kiwifruit (A. chinensis var. deliciosa C.F.Liang & A.R.Ferguson), little is known about the nutrient requirements, leaf tissue sufficiency levels, or optimum time and method of leaf sampling in hardy kiwifruit. The objectives of this study were to determine whether leaf sampling should be conducted based on phenology or calendar date, and to identify best practices for sampling. Leaves were sampled from determinate and indeterminate shoot types separately from male and female vines every 2 weeks from mid-May to late October, starting when flower buds reached 6 mm in diameter and finishing after fruit harvest. Leaf nutrient concentration varied by year, plant gender, and shoot type for many nutrients and sampling dates. Key plant developmental stages were 2 weeks earlier in 2009 than 2008 despite fewer cumulative growing degree days (GDD) at each phenological stage in 2009, except at harvest when there were more GDD in 2009. Patterns of change in nutrient concentration were similar between years, and did not always match the 2-week shift in phenology. Female vines had higher concentrations of N, K, S, Cu, and Zn early in the season, but were similar to males later in the season. For other nutrients, including P, Mg, Ca, Fe, and Mn, females had consistently higher leaf concentrations across the whole season. Shoot type affected the concentration of many nutrients in both female and male vines for many sampling dates, but generally followed the same pattern of change through the season. The currently recommended leaf sampling time for kiwifruit vines in the northern hemisphere is August. While there were phenological differences between years, calendar-based sampling in mid-to late-August provided a better window of relative stability for most nutrients than phenology-based sampling for female vines. When compared to existing available standards for fuzzy kiwifruit, the hardy kiwifruit in this study often fell outside of the recommended ranges and, for B, into the excessive range, suggesting revisions to nutrient standards for hardy kiwifruit in Oregon may be appropriate.