｢毛管給水ひも」によるトマト栽培の可能性について

This research was conducted to investigate any potential problems that may be encountered while using capillary wick irrigation system. Medium-fruited tomato plants were cultivated in spring up to the 10th truss. In the first experiment, a 1/5,000a wagner pot was used, and small openings were made 5mm or 50mm from the bottom of the pots. Capillary wicks, 4 cm in width and 45 cm in length were inserted into the slits and aligned to the pot’s inner wall perpendicularly to the soil surface. The other end of the wick was dipped in half or full strength Ohtsuka-A nutrient solution. The wick was covered with water permeable root-barrier material to prevent root penetration into wick. This resulted in good growth and relatively high yield. Without covering, roots grew vigorously into the wicks and 1 month after transplanting extended to the reservoir solution. Removal of root overgrowth caused wilting in some of the plants. This symptom was more pronounced where the wick insertion points were 50 mm from the base. Root contexture was observed in non-covered and imperfectly covered wicks. These results indicate that it is important to make a wick with a perfect covering for stable plant growth and fruit yield. In the second experiment, the capacity of 2 cm or 4 cm wide with and single or double layers of capillary wicks to transport water to the plant root-zone was examined. Some of the plants wilted in the 2 cm single layer, while no differences were observed in other treatments. Furthermore, a high percentage of blossom-end rot was recorded in all treatments. In response to water uptake by the plants, the nutrient solution was supplied daily depending on the decrease of water in the reservoir, in order to maintain the water level fluctuation within a 3 cm range. This fluctuation may account for the blossom-end rot prevalence observed, probably due to water-stress imposed on the plants by unstable water level in the reservoir.

「毛管給水ひも」によるトマト栽培の可能性を探るため，中玉トマトの10段摘心栽培を試み，ひもの特性と栽培上の問題点を明らかにした．1/5,000ａワグネルポットの底から5㎜位と50㎜位に小穴を開け，そこへ毛管ひも（幅4㎝，長さ45㎝）の一端を導入し，そのまま鉢中央を横切り対壁に沿って土壌表面まで配置した．他の一端は培養液に浸した．この毛管ひもを遮根透水シートで被覆し（接着あるいは機械織りによるチューブ状管にひもを挿入），その「被覆ひも」を「無被覆ひも」と比較したところ，被覆ひもでは根の侵入が強く抑制でき成育が旺盛で収量も高かった．被覆しないと1か月後には根が毛管ひも内に伸長して貯液槽にまで達した．この根を除去すると多くの個体は萎れの症状を呈した．この症状は50㎜位の方が著しかった．被覆が不完全だと接着部あるいは織り込み部から根は毛管ひもに侵入する．従って，毛管ひもは完全被覆されることが重要であるといえる．また，遮根透水ひもを2㎝幅，4㎝幅としシングル状とダブル状で比較したところ，成育半ばでシングル2㎝幅では萎れ症状が観察され枯死する個体も現れた．その 他では成育等に大きな差異は認められなかったが，いずれの処理区においても多くの尻腐れ果が発生した．トマトの吸水に伴って水位は低下するため本試験では毎日，培養液を手で補給した．しかし，水位変化は最大で3㎝と大きかった．尻腐れ果発生はこの液槽の水位レベル管理に起因するところ大と推察され，今後の課題として残された．