Relationships between Crown Density, Yield and Leaf Area Index in Different Planting Densities in Wase Satsuma Mandarins (Citrus unshiu Marc. var. praecox Tanaka)

Abstract

Two-year-old trees of ‘Miyagawa Wase’, an early-maturing cultivar of satsuma mandarin, were planted in 1967 under four different planting densities: 1, 250, 2, 500, 5, 000 and 10, 000 trees/ha. The relationships between crown density and yield, and between crown density and leaf area index (LAI) were investigated from data obtained from 1969 to 1986 (tree age 4 to 21 years). The contribution of several factors such as crown density, LAI and planting density affecting yield was also determined.
1. The relationships between crown density and yield, and between crown density and LAI showed a close fitness to the quadratic curve proofs. Quadratic regression coefficients became smaller as planting density increased. Yield per unit leaf area decreased with increasing planting densities.
2. The crown density which gave the highest yield (64t/ha) was estimated to be 99%, as the quadratic curve showed. At this time LAI was estimated to be 6.8. LAI then increased toward the highest value (8.2) during six years after the orchard was almost covered by foliage.
3. In analyzing variation of yield, LAI made the greatest contribution. The contribution of crown density and planting density to yield was so small that effects of these factors were expected to be largely due to their influence on LAI.