Technical Improvement of Soil Moisture & Nutrition Management on the Slope Land of Citrus Orchards
Huang, H. Y. and C. J. Leu
In general, the soil of slope land orchards in southern Taiwan is low in organic matter (0.7~1.5%), low in pH value (4.0~5.2) and lack of irrigation facilities that resulted in a very serious problem of soil erosion. Soil & water conservation was also poor. Because the soil of Hsinhua ranch station is very typical, one hectare of a 5-yr old orchard of sweet orange was used in this study for the improvement of irrigation and fertilizer application system. The results from 1987 and 1990 are summarized as follow: (1) The cost of the dripping irrigation system is ca. NT$60,000 dollars/ha which is acceptable to most of the farmers, however, the nozzle and uneven flow rate in the pipes should be improved. (2) The diffusion area of water on the soil surface was 10~15 cm in diameter, and the water moved vertically in a sector shape downward to 1 meter in depth. (3) During the dry season, if the dripping irrigation condition controlled at 60~80 liters/tree/10 hrs, the water potential in the soil can maintain between –0.3~-0.5bar in 7~20 days. (4) When the liquid fertilizer of Taiwan Fertilizer Co. (300 dilutions) was mixed into the irrigation system, the application cost of labor reduced. NT$3,000 dollars/ha/time, comparing to the hand application of solid fertilizers. (5) Application of organic fertilizer at the rate of 30kg tree/yr significantly increased the organic matter content of the soil, and the application of calcium carbonate powder at the rate of 2 kg/tree can maintained the soil at high pH value condition in 6 months and then return to the original level. (6) The trunk diameter of the dripped trees increased 11.3% in 2nd year, fruit weight increased 14%, sugar content increased 0.7 Brix and acidity decreased.
Accepted for publication: May 23, 1991.