Abstract
Effects of liquid fertilizer application on soil chemical properties of satsuma mandarin (Citrus unshiu Marc.) trees grown in pots filled with granite soils were investigated under a plastic house. The effects of a liquid fertilizer were compared with those of three types of pellet-shaped solid fertilizers. For preparing the liquid fertilizer, water-soluble solid fertilizer (N-P_2O_5-K_2O=15-15-10) was diluted 1:150 with water. It was applied as overhead spray or as soil drench at a rate of 231 mL in a pot equivalent to 1.39 mm water 18 times in a year. The repeated liquid fertilizer application lowered soil pH. In the upper soil layer, the liquid fertilizer application increased inorganic nitrogen and exchangeable potassium content, while exchangeable calcium and magnesium contents were decreased. The available phosphorus content in the upper soil layer in the liquid fertilizer plots was among those of three types of pellet-shaped solid fertilizer plots. Our results by pot tests indicate the possible alternative way of fertilizer application but further experiments in the commercial satsuma mandarin orchards by using sprinkler systems are needed.
