Effect of planting density on dry matter partitioning in young ‘Laetitia’ / ‘Marianna’ plum trees grown in lysimeter tanks

Abstract

The effects of increasing planting density on young Iysimeter tank-grown plum trees were investigated. Seasonal increases in stem circumference, and average shoot lengths, decreased significantly (P = 0.05) as the number of trees per 1.4 x 3.0 m tank increased from one to three. Total single-tree dry masses after three seasons were smaller, by 17.8% in the 2-treetank· 1 and 53.2% in the 3-tree tank-I, than in the 1-tree tank-I treatment. Corresponding decreases in fruiting spur dry mass (OM) tree-\ were 46.3% and 64.8%. Ratios of topgrowth (above graft union) OM tree-I to rooting system (below graft union) OM tree-I increased from 1.98 to 2.62 to 3.04 in the 1-, 2-and 3-tree tank-\ treatments, respectively. Branch OM made up 26.5%, and stem OM 68.9%, of the single-tree topgrowth OM in the 1-tree tank-\ treatment but, in the 2-and 3-tree tank-i treatments, branch OM increased to approximately 60.3%, and stem OM decreased to approximately 35.9% of the topgrowth OM. Leaf, fruit, shoot and < 3 mm diameter root nitrogen contents increased with planting density. By extrapolation, total tree OM ha-\, and fruiting spur OM ha-I , are greater at 4762 than at 2381 or 7143 trees ha-I .