Runoff characteristics of nutrients from citrus fruit grove and its effects on water area

In this study, field observations are carried out in order to make clear the runoff characteristics of pollutants from citrus fruit grove, especially nutrients such as nitrogen, phosphorus and other inorganic materials. Long-term observation in the test fields continued for more than 7 months and detailed observations during one rainfall are also carried out. From these observations, the following results are obtained. 1) Nitrogen concentration in grove soil leachate is usually in a range of 25 to 45 mgN/L, and the main component is nitrate, whereas phosphorus concentration is in a range of 0.1 to 0.8 mgP/L and the main component is phosphate. Concentration of nutrients is higher than that in environment around it. 2) Runoff loading rate of any materials from grove soil can be unified and expressed as a power function of the flow rate. In this case, runoff style of each material is characterized by the power coefficient betax. 3) It is understood that the runoff characteristics are affected by the pH and rate of rainfall, and the ways of affecting the runoff characteristics are different in each material. 4) It is also suggested that detailed investigations are required to estimate the effect of pollutant runoff because the runoff characteristics are widely changed by the rainfall characteristics.