Effects of fertilization methods on N-uptake, vegetetive growth and yield of forcing strawberry

To establish labor-saving and efficient fertilization methods in strawberry culture, field experiments were conducted using different blending ratios of Cyclo-Di-Urea (CDU) compound fertilizer (15-15-15) and sigmoid types of polyolefin coated urea (POCUS, 40-0-0); the other two are: POCUS80 (D1=40, D2=40) and POCUS120 (D1=60, D2=60). The blending ratios of fertilizer were compared with conventional fertilization method: broadcast application of C DU compound fertilizer: POCUS80: POCUS120 = 15:45:40), band application (5: 45:50) and hole application (4:43:53). The application rates of N-fertilizer were reduced 20%, 35%, and 50% for br oadcast, band and hole application, respectively, as compared to the recomm ended application rate of nitrogen fertilizer in Kumamoto prefecture (24 g. m(-2)). 1. The average fresh weight of plants in middle growing stage was in the fo llowing order : hole >band>broadcast application. 2. The total yields from the three fertilization plots with POCU fertilizer s were almost the same as that for conventional fertilization although the amount of N was reduced. The average fruit weight and the percentage of A-c lass fruit (good shape and 7g<) were almost same in each treatment. 3. The N-uptake by plants in the hole application exceeded those of plants in the broadcast and band application throughout growing period. 4. The concentrations of residual inorganic N in the soil from band and hol e applications remained below the nontoxic level to strawberry plants. Base d on our results, we conclude that a single basal application of polyolefin coated fertilizer with reduced leveled of nitrogen is highly feasible for strawberry culture because no significant decrease in fruit yield and quali ty were observed.