Relation between Yield and Leaf Area Index in Different Planting Densities under Different Cultural Treatments in Satsuma Mandarin (Citrus unshiu Marc. var. praecox) Tree

Abstract

Two-year-old trees of ‘Miyagawa Wase’, an early maturing variety of satsuma mandarin, were planted in 1967 at various planting densities, and grown under different cultural treatments until they were 19 years old.
Planting densities were 1, 250, 2, 500, 5, 000 and 10, 000 trees/ha. Cultural treatments were shallow plowing+less fertilization, deep plowing+standard fertilization, with either no pruning+no fruit thinning or pruning+fruit thinning.
Effects of planting density and cultural treatment on leaf area index (LAI) were determined from data obtained during the period from 1969 to 1984 (tree age 4-to 19-year-old).
LAI which gave a maximum yield was determined at each tree age, and the relation between LAI and yield was also examined.
Results and conclusions were as follows:
1. The shallow plowing+less fertilization showed a slightly lower LAI level than the deep plowing+standard fertilization. The no pruning+no fruit thinning showed a slightly higher LAI level than the pruning+fruit thinning.
2. LAI increased with tree age at each planting density, and the higher the planting density, the larger the rate of increase became. After LAI had reached a maximum at each planting density, it levelled off with a large yearly fluctuation in higher planting densities.
Average LAI for the levelled off values were 6.0 at 1, 250 trees/ha plot, 6.7 at 2, 500, 8.0 at 5, 000, and 8.7 at 10, 000. Thus the higher the planting density, the larger the LAI became.
3. The average maximum yield for all tree age (4-to 19-year-old) was 67t/ha, and average LAI which gave it was 6.7. Yield per unit leaf area was 1kg/m².
4. The optimum LAI which gave the highest yield (74t/ha) was estimated to be 6.7 in the lower planting density.