Adding value to green tea by reducing nitrogen loading in tea cultivation using spent coffee grounds
2023
Shimomuki, T.
Tea production has been increased continuously in the world. However, both production and consumption in Japan have been declining year by year, and the number of tea growers have also been decreasing significantly. Green tea has been applied nitrogen (N) fertilizer much more than the other agricultural products to achieve high prices. The N fertilizers application shows to stimulate amino acid synthesis and improve yields. High fertilizer application does not necessarily to lead to a proportional increase in crop yields, and residual N might release to the environment. On the other hand, in Japan, spent coffee grounds (SCG) are emitted in large quantities every year as food waste, most of which is incinerated. SCG have been shown to improve soil aeration and aggregate structure, rich in nutrients, and low risk of heavy metal pollution. In this study, authors investigated to find an optimal fertilizer design for tea cultivation that can maintain tea production and reduce N discharges from the soil by applying SCG. The results of cation exchange capacity (CEC) of soil showed higher values in the test plot with SCG than in the test plot without SCG, up to 5.5me/100g in plot Zero (no-fertilizer) compared to C (SCG only) and F2C (Fertilizer + double weight SCG). The total amount of NO sub 3- and NO sub 2- discharges in soil water were lower in all test plots where SCG was applied compared to plot F. The N loading rate (N loading/applied Nx100) were 26.12-19.68% in SCG applied plot, compared to 86.85% in the conventional plot. Tea yield was increase in SCG application plots than conventional, with the order of increase being 0.8F1C 13.9% F1C 9.2% F2C 1.15%. The total amount of N in the leaf was lower in the test plot where SCG was applied compared to plot F.
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