Fertilizer Management in Tea Cultivation
In tea cultivation, fertilizer management is an extremely important factor. This is because the quality of Japanese tea is determined by the amino acid content contained in the product. The tea plant absorbs nitrogen through its roots and uses it as a raw material to synthesize amino acids. During the Shincha (new tea) season, these amino acids are supplied to the new buds, and the buds grow. Since the nitrogen source essential for this amino acid synthesis depends on fertilizer, fertilizer management becomes a major factor in determining the quality of the tea.
What is particularly important in tea fertilizer management is the timing of the application. Even with the same fertilizer and the same amount, the effect changes significantly depending on the timing of the application. General fertilizer management for tea consists of summer fertilizer (around August), autumn fertilizer (around September to October), spring fertilizer (around February to March), and budding fertilizer (around April). Since the Shincha season is in the spring, some may wonder if fertilization from the summer to autumn of the previous year is really necessary. However, theanine—the representative amino acid of tea—is produced and accumulated based on nitrogen absorbed the previous year and is supplied to the new buds the following spring. Therefore, it can be said that tea fertilizer management is important throughout the entire annual cycle.
In our own tea gardens, we mainly perform fertilization three times a year: once between August and September, once around October, and once around March of the following year. For the fertilizer from summer to autumn, we apply a "bokashi" fertilizer that contains a lot of animal-based materials with sufficient nitrogen. The fertilizer applied around March is a special one using microbial materials. This fertilizer decomposes easily even at low temperatures and is expected to provide nitrogen even in early spring when the soil temperature is low. In organic cultivation, we cannot use fast-acting chemically synthesized fertilizers, and since there are no substitutes for the materials used as budding fertilizers, we settled on the fertilization design mentioned above.
Fertilization work is quite heavy labor, and it is a difficult task to apply several hundred kilograms of fertilizer to a single field. This kind of year-round management ultimately shows up in the quality of the first-flush tea (Ichibancha), so I work on it daily using that as my motivation.
By Aka Hiroki.
