素焼パイプを用いた地下自動潅水法による育苗及び挿し木について

Abstract

素焼多孔質管を用いた地下潅水法による作物の栽培は古くから実用化が試みられてきたが, 木本の育成についてはほとんど応用されていない。本研究は普通の陶土を1, 100℃で焼結した外径3cm, 浸出面長20cmの素焼パイプの給水性能と, 造園用樹木の育成ならびに挿し木に対する効果をプランターを用い温室内で検討したものである。その結果, 以下のような特性が明らかになった。1) 給水量は正圧の方が著しく大きく, また負圧が大きくなるほど減少する。いずれも土壌表面からの蒸発量と比例する。2) 腐植質や砂を混合した空隙の多い用土より, 田土のような粒径の細かい土壌の方の給水量が多い。3) 土壌湿度は素焼パイプから隔たるにしたがって同心円的に減少する。4) 造園用苗木を27ヵ月間育成した結果, サツキとサザンカは負圧 (設定水頭-13cm) の方が, カナメモチは正圧 (+20cm) の方が良く成長した。この間の給水量は気温が高くなるほど多くなった。5) サツキ, サザンカ, カナメモチの挿し木の発根状態は手潅水より-1cmの負圧潅水がよかった。以上から, 自動的, 連続的に給水の可能な素焼パイプによる地下自動潅水法は, 苗木の育成, 挿し木養苗にきわめて有効であるといえよう。

Long-term studies have been conducted on the practical cultivation of several crops by a subsurface irrigation system using a porous ceramic pipe, but cultivation of young trees by this method has not been reported. This paper discusses the property of the water supply from the porous ceramic pipe made of pottery clay baked at 1, 100℃, and 3 cm in diameter and 20 cm in length on seepage outside. Furthermore, the effects of subsurface irrigation for long-term cultivation of garden trees and rooting of cuttings in a plastic container in a greenhouse are reported. 1) The water supply by the positive pressure in a ceramic pipe is much larger than the negative pressure, and its quantity gradually decreases towards the higher negative pressure. In general, a positive correlation exists between the quantity of water supply from pipe and the quantity of evaporation from the soil surface. 2) The water supply for the fine clay such as a rice field soil is much larger than the porous loam mixed with humus and sand. 3) The soil moisture decreases conformably to concentric circles from the porous ceramic pipe. 4) Cultivation of garden seedlings for 27 months revealed more vigorous growth for Rhododendron indicum SWEET and Camellia sasanqua THUNB. grown at a negative pressure (difference of water level between ceramic pipe and tank : -13cm) and for Photinia glabra MAXIM. grown at a positive pressure (+20cm) compared to those grown at positive and negative pressures, respectively. The water supply increased with the incraese in temperature for three seasons. 5) The rooting rate of cuttings of Rhododendron indicum, Camellia Sasanqua and Photinia glabra in a negative pressure of -1cm level was markedly larger than that of the hand-irrigated cuttings. As mentioned above, the subsurface irrigation method by the porous ceramic pipe having the characteristic of self-controlled and continuous irrigation may be useful for the cultivation of seedlings and cuttings.