液肥の散布が花崗岩由来ウンシュウミカン園土壌の化学性に及ぼす影響(土壌管理・施肥・灌水)  [in Japanese] Effects of Overhead Mixed Liquid Fertilizer Application on Sandy Soil Chemical Properties of Satsuma Mandarin Orchard(Soil Management, Fertilization & Irrigation)  [in Japanese]

ウンシュウミカンにおける液肥樹上散布(スプリンクラー施肥)が土壌(マサ土)の化学性に及ぼす影響を明らかにするため,1年生'宮川早生'(台木はカラタチ)を植えた50Lの樹脂製ポットで散布試験した.試験区として無施肥区,有機配合区および液肥区(濃度と施用回数を変えた4区)の計6区を設定した.液肥として水溶性粉末肥料(窒素15%,リン酸15%,加里10%)の150倍液と300倍液を用いた.液肥は5月31日から1年間,6回あるいは18回,じょうろを用いて樹上から均等に散布した.液肥区の土壌pHは有機配合区に比べて低くなり,この傾向は300倍液に比べ150倍液を散布した場合に顕著に低下した.150倍液を散布した区は,置換性石灰と置換性苦土の低下が大きかった.液肥の施用回数を多くするほど,無機態窒素の増加が速やかとなり,上層土のリン酸と加里も増加した.上層土から下層土へのリン酸と加里の移動は,液肥と有機配合肥料で同等であった.これらの結果から,液肥の施用は無機成分の速やかな供給に効果的と考えられ,節水と施肥労力の軽労化のためには,水溶性粉末複合液肥の150倍液の年間6回散布(25mmかん水相当)が有望と考えられる.

Effects of mixed application of liquid fertilizer on the sandy soil chemical properties of a satsuma mandarin (Citrus unshiu Marc.) orchard were investigated. One-year-old trees of 'Miyagawa Wase'/trifoliate orange rootstocks planted in a 50 L pot were used for the plots. Six plots were settled. One was a non-fertilized plot, the others were solid fertilizer (control) and four liquid fertilizer application plots. Liquid fertilizer was prepared by dissolving solid mixed fertilizer containing 15% nitrogen, 15% phosphorus and 10% potassium in water at 150- and 300-fold dilution. Each dilutions of liquid fertilizer were applied six times or eighteen times starting from the end of May during the one-year experimental period. Mixed Liquid fertilizer application lowered soil pH compared with solid fertilizer application and the tendency was greater at 150-fold than at 300-fold dilution. In relation to this, 150-dilution application of mixed fertilizer lowered exchangeable calcium and magnesium concentration in the soil. The more frequent the applications of liquid fertilizer, the more rapid the increases in the nitrogen content in the soil. Phosphorus and potassium concentrations in the upper soil layer increased in response to liquid fertilizer application. The downward movement of phosphorus and potassium from the upper to lower soil layers showed a pattern similar to that after solid fertilizer application. These findings indicate that the mixed liquid fertilizer application is effective in the immediate supply of inorganic nutrients but that lime application is necessary for soil pH amendment.