Foliar spray - Yomensanpu

This refers to spraying a thin liquid fertilizer onto the leaves so that the fertilizer components can be absorbed by the plants. Normally, the inorganic components necessary for crops are applied to the soil as fertilizer, and are absorbed and used by the roots, but since plants can absorb nutrients not only through their roots but also through their leaves, foliar spraying is used as a supplementary or emergency measure for fruit trees and flowers, which are valued for their taste and color, and for vegetables with large leaves.

The inorganic components sprayed are trace elements (also called micronutrients) such as iron, zinc, magnesium, and boron, which are needed in small quantities by crops and are fixed or difficult to move when applied to the soil. Macronutrients such as urea are also used for foliar spraying because they are less likely to cause damage, but the absorption varies greatly depending on the type of crop and weather, and there are restrictions such as not being able to make the concentration too high, so foliar spraying of macronutrients is merely supplementary.

[Yuki Koyama]

Fertilizer Association Newspaper Division, Fertilizer Yearbook, various editions (Fertilizer Association)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

肥料成分を植物に吸収させるために液状にした薄い肥料を葉面に散布することをいう。通常、作物に必要な無機成分は土壌中に肥料として施され、根から吸収、利用されるのが本筋であるが、植物は根ばかりでなく葉からも養分を吸収できるので果樹や花卉(かき)のように味、色の商品性を重んじるもの、葉の大きな野菜などで補助的、応急的な手段として葉面散布が行われる。

　散布される無機成分は作物の必要量も少なく、しかも土壌に施すと固定されたり移動しにくい鉄、亜鉛やマグネシウム、ホウ素などの微量要素（微量養素ともいう）である。尿素のような多量要素も薬害が出にくいことから葉面散布に使用されているが、作物の種類や天候などにより吸収状況が大きく異なり、また濃度をあまり濃くできないなどの制約から、多量要素の葉面散布はあくまでも補助的なものにすぎない。

［小山雄生］

『肥料協会新聞部編『肥料年鑑』各年版（肥料協会）』

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