The effects of organic fertilizers on yield, quality and antioxidant activity in tea (Camellia sinensis L.)

In recent years, the use of organic fertilizers, as an alternative to inorganic fertilizers, has been increasing worldwide due to the negative effects of chemical fertilizers on the environment, sustainability of natural resources and human health. In this context, the determination of the effects of organic fertilizers on yield and quality criteria in tea is extremely important. This study was conducted to determine the effects of different organic fertilizers on fresh leaf yield, total phenolic substances, caffeine and catechin compounds, and antioxidant activity in tea (Camellia sinensis L.) plant. The two-year research was carried out at three locations (Pazar, Musadağı and Ortapazar) with different altitudes. In the study, in addition to the inorganic fertilizer (25-5-10) traditionally used in tea production, 3 solid organic fertilizers (K1, K2 and K3), 2 liquid organic fertilizers (S1 and S2) and 1 liquid + solid organic fertilizer combination (S+K) were applied and fresh tea leaves were harvested in three shooting periods (may-june, 1st harvest; july-august, 2nd harvest and september-october, 3rd harvest). In the experiments, fresh tea leaf yields were determined based on shooting period and in total annual, and total phenolic substances, caffeine and catechin compounds, and antioxidant activity analyzes were performed in fresh tea leaves. As a result of the research, fresh leaf yield increased by up to 100% with inorganic fertilizer and 74% with solid organic fertilizers compared control with no fertilizer application. The effect of liquid organic fertilizers and the combination of liquid + solid organic fertilizer on fresh leaf yield is generally not different than the control. In terms of caffeine content, an increase of around 29% was recorded in inorganic fertilizers and solid organic fertilizers. In general, total phenolic substances, antioxidant activity and catechin compounds increased the most in the liquid + solid organic fertilizer combination. The effects of organic fertilizers in different form and content on fresh leaf yield, quality criteria and antioxidant activity varied depending on harvest periods, altitude and years.