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Effects of foliar sprays on plum development and production under Latvian conditions

Gravite, I., Kaufmane, E.
Acta horticulturae 2017 no.1177 pp. 355-360
Prunus domestica, air temperature, boron, budbreak, calcium, cultivars, flavor, flowering date, foliar spraying, fruit yield, fruits, plums, pollination, rain, spring, summer, trees, winter, Latvia
A study of the effects of summer foliar sprays of Ca or B on plum trees (Prunus domestica) was conducted over 2 years (2012 and 2013) in Latvia with two plum cultivars 'Sonora' and 'Edinburgas Hercogs'. Both years had unusual weather, which significantly influenced the health and yield of the trees. In 2012 the yield of both plum cultivars was very low because winter cold started in the 2nd half of January, when the majority of cultivars had not developed sufficient resistance to low temperatures, which caused significant bud damage. The spring of 2013 had a rapid increase of temperature which caused plum flowering two weeks after bud break. This was followed by intense rainfall (60 mm in two days) during flowering, along with high air temperatures (+29°C), which had a negative effect on pollination. Fruit yield, depending on cultivar, was 0.02-0.49 kg cm-2. In the summer of 2013, uncommonly high temperature had a negative effect on fruit quality of 'Sonora'. The fruits matured very rapidly, colored and softened very early, without developing good flavor. Foliar sprays of boron increased yield, quality and delayed maturation while calcium foliar sprays tended to advance flowering date.