異なった栽植密度におけるワセウンシュウの果実生産力, 葉面積指数及び樹冠占有面積率と収量との関係

Abstract

Two-year-old trees of ‘Miyagawa’ Wase, an early maturing cultivar of satsuma mandarin, were planted in 1967 at various planting densities and grown until they were 21 years old. The effect of planting density on fruit productivity (bearing amount per unit leaf area), yield per unit land area, leaf area index (LAI) and crown density, and the relations between fruit productivity, LAI, crown density and yield were determined in lower planting density (1, 250 and 2, 500 trees/ha) and higher planting density (5, 000 and 10, 000 trees/ha).1. While fruit productivity showed a slight decrease from 1.21kg/m2 to 1.00kg/m2 with an increase of tree age from 10 to 21 in lower planting density, it showed a large decrease from 0.93kg/m2 to 0.50kg/m2 with an increase of tree age from 4 to 17 in higher planting density. Higher planting density showed larger LAI and crown density than lower planting density at any age.2. The relations between LAI and fruit productivity, and between crown density and fruit productivity showed that fruit productivity hardly changed when LAI and crown density were lower than 5 and 80%, respectively, but decreased when they were over these values.3. An increase in yield for early-stage trees was mainly dependent on a rapid increase in LAI or crown density, and a subsequent decrease in yield was mainly dependent on a large decrease in fruit productivity.4. Yield (60t/ha) in the higher planting density was nearly equal to that in the lower planting density (60t/ha) for 11-year-old trees. The higher planting density had the superior yield for trees younger than 11 years old, but after 11 years its yield was surpassed by the lower planting density.