''Hibai'' refers to the artificial replenishment of nutrition, such as fertilizer, in the course of cultivation. There are many nutritive substances in natural soil that are essential for plants to grow. However, those substances are not necessarily in a good chemical form for plants to absorb from roots, so there is a need to provide artificial fertilizers. Among such fertilizers are solid ones which dissolve in irrigation water and soak though soil. Liquid ones are mostly concentrates, so they should be attenuated before spraying. Besides the solid and liquid ones, there are soil-activating agents which transform chemical forms of natural nutritive substances in soil to help plants absorb them more easily.
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