The Control of Magnesium Deficiency in Apple Rootstock Stoolbeds

Abstract

Trials lasting nine years have been conducted on two types of magnesium- deficient apple rootstocks to assess the curative value of foliar sprays and/or soil applications of Epsom salt (MgS04.7H20).After the first year, M.IV rootstocks sprayed with 2% Epsom salt solution produced more, larger, and better-rooted shoots than did the untreated plants, giving more than a 60% increase in numbers of high-quality rooted shoots, and three sprayings were as effective as nine. The implications of this finding are discussed.In contrast to M.IV, spraying MM.102 rootstocks did not lead to a sustained improvement in quality of rooted shoots even though symptoms of magnesium deficiency were eliminated and the number of shoots increased. Elimination of foliar symptoms is therefore, of itself, no indication of economic improvements of growth. It is concluded that some other factor, perhaps potassium deficiency, limited growth.Foliar sprays applied nine times annually to M.IV rootstocks raised the percentage of magnesium i...