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Abstract
Tree density (222-801 trees/ha) affected growth of roots in plantings of ‘Washington’ navel orange (Citrus sinensis (L.) Osbeck). Root spread, circumference, and root size were greater on wide spaced trees than on closely planted trees which had overlapping root systems. Roots of closely spaced trees were shorter in length and smaller in size.
Abstract
The effect of tree spacing on the root distribution of 9-year old ‘Washington’ navel orange trees on ‘Troyer’ citrange rootstock was studied. Spacings ranged from 9 ft x 15 ft to 22 ft x 22 ft. Roots were washed from soil cores (3-ft deep, 4-inch diam) taken at 2-ft intervals along 2 transects, 1 across the row and 1 along the row and beneath an irrigation furrow. The distribution of both small roots (1.5 mm in diam or smaller) and large roots was affected by tree spacing and by location of the irrigation furrow. At close springs, many soil cores contained about 4 g dry wt of small roots, suggesting that the soil contained as many feeder roots as possible under those conditions. Wider spacings had fewer roots per core. Evidence suggests that considerable overlapping of root systems occurred at close spacings but not at the wider spacings. It is likely that root competition will limit yield during the next decade at the closer spacings, whereas considerable room for root growth exists at wide spacings.
Abstract
In 1961, trees of Frost Nucellar ‘Washington’ navel orange on Troyer Citrange rootstock were planted at eleven different spacings to determine the effect of tree spacing on growth, production, and fruit quality. Growth rate as measured by trunk circumference was proportional to decreasing tree density or increased spacing. The wider the spacing, the greater was the trunk circumference and the fruit-bearing capacity of the tree. Shading of skirt foliage, as closely planted trees began to crowd, caused the skirts to die and decreased production. Pruning to keep these trees from crowding reduced yield in proportion to the amount of foliage removed. Removal of alternate trees in the two most densely planted spacings, 9 ft. × 11 ft. and 11 ft. × 11 ft., reduced competition and allowed more light to reach the remaining trees. Skirt foliage regrew and yield per-tree and per-acre increased.
Fruit colored faster and was larger on the widely spaced trees, where less shading had occurred, than on closely spaced trees. Fruit quality analysis showed no difference in percent of juice, soluble solids, acid, or rag, or in peel and rind thickness.
The closest spacings, 9 ft. × 11 ft., 9 ft. × 15 ft. and 11 ft. × 11 ft., operated at a net loss for the first five years of production. Although per tree production was highest on the widest spacing, 22 ft. × 22 ft., net returns per acre on this spacing are still low because of the number of trees per acre. The 11 ft. × 22 ft. spacing with 180 trees per acre had the largest net income per acre.
Abstract
High density planting of tree crops has the potential of increasing yield and income during the early years of an orchard’s life. Eleven different planting densities of citrus were studied over a 10-year period to determine the effect of tree spacing on yield, tree growth, root distribution, nutrition, and economic factors involved. Extremely close plantings soon crowded to the point where they were unmanageable and tree removal became necessary. Pruning was needed to maintain a workable orchard in more moderatley spaced plots.