Determination of Application Rates of Nitrogen Fertilizer for ‘Shiranuhi’ Mandarin in Plastic Film Houses Using Soil Electrical Conductivity

In this study, we developed an equation to determine nitrogen fertilizer rates for ‘Shiranuhi’ mandarin [(Citrus unshiu × C. sinensis) reticulata] growing soils in plastic film houses prevent salt accumulation and maintain optimum nutrient levels. We analyzed the amount of applied fertilizers, soil chemical properties, yields from 45 farms that vary concentrations on Jeju Island, Korea. The results revealed average property values, such as electrical conductivity (EC), available P2O5, exchangeable cations (K+, Ca2+, Mg2+), were higher than acceptable range, except pH organic matter. showed amounts phosphorus through application (N 327 kg ha-1, P2O5 294 K2O 236 ha-1) standard rate cultivation mandarin. EC values NO3-N concentration had a close correlation (r = 0.96, p < 0.001). did not differ with fertilizers while there was significant negative -0.455, 0.01) -0.476, soils. Our demonstrated has substantial effect value. Soil levels may recommended depending each tree’s age.Recommended (N) according (EC) tree ages cultivated Island. Tree (years) N recommendation equation† (dS m-1) 0.5 1.0 2.0 4.0 Recommended (kg 1 - 5 Y 1.6273X + 18.065 17.3 16.4 14.8 11.6 6 10 8.1363X 90.323 86.3 82.2 74.1 57.8 11 15 16.273X 180.65 173 164 148 116 16 20 24.409X 270.97 259 247 222 21? 32.545X 361.29 345 329 296 231 †Y: ha-1); X: