This study was conducted to investigate the changes in soil water potential to maintain the optimum soil water condition for the improvement of fruit quality by polyethylene(P.E.) film mulching and root pruning during the period from August 28 to November 18. Soils used in this experiment were black volcanic ash soils and fruit trees were Satsuma mandarin (Citrus unshiu). Soil water potential was measured with self-made gypsum block. Average bulk density, particle density and porosity of the soils were 0.70g/㎤, 2.40g/㎤, and 71 %, respectively.
Soil moisture content before the treatments was slightly lower than field capacity. Soil water potential in P. E. t71m mulching was rapidly lowered and maintained below -1.0 ㎪ after 20 days and 30 days at 10㎝ and 30㎝ soil depth, however, that in control was maintained about -0.1 ㎫ after 40 days. Degrees of saturation of the soils before the treatments were in the range of 47∼51 %, among 4 treatments shown no significant differences. At harvest, degree of saturation in P. E. film mulch was 28%, being 9.5∼20.2% lower than other treatments.
Reltative increase of fruit width during the period from Aug. 28 to Nov. 18 was 134% in P. E. film mulching and 138% in root pruning+P. E. film mulching, and 142% in control. Soluble solids content before the treatments was 6° Bx, without any difference among the treatments. At havest, the soluble solids content in P. E. film mulching was 11.6° Bx, being 1.9∼2.3° Bx higher than other treatments. Soluble solids content in fruit juice was negatively correlated with fruit width and soluble solids content in P. E. film mulching was about 2° Bx higher than other treatments with same fruit width.
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