Abstract: Disclosed is a method for cultivating a citrus plant, comprising: applying to the citrus plant a liquid composition comprising Fe ions, wherein at least a portion of the Fe ions are Fe2+ ions, wherein the citrus plant is cultivated in sandy soil.

Abstract: Disclosed is a method for cultivating a citrus plant comprising: applying to the citrus plants a liquid composition comprising Fe ions and humus acids, wherein at least a portion of the Fe ions are Fe2+ ions.

Abstract: A liquid humic acid extract that does not form precipitates when combined with a liquid fertilizer containing at least one of Mg, Fe, Zn and Mo and having an electric conductivity of 90 ms/cm or more. A liquid humic acid extract containing humic acid that has a mass-average molecular weight of 100 to 1,200, and having a total organic carbon concentration of 15,000 to 25,000 mg/L and a pH of 0.5 to 4.0. Preferably, the liquid humic acid extract contains a humic acid having a mass-average molecular weight of 100 to 1,200, and has a total organic carbon concentration of 15,000 to 25,000 mg/L and a pH of 0.5 to 4.0. A liquid humic acid extract that hardly forms precipitates and realizes an increase in the crop yield.