Appropriate Nitrogen Form and Application Rate Can Improve Yield and Quality of Autumn Tea with Drip Irrigation

Abstract

Applying nitrogen fertilization is an important way to improve the yield and quality of autumn tea (Camellia sinensis L.), but the effects of nitrogen application rate and nitrogen form still remain unclear. Field experiments were conducted in a drip-irrigated tea garden in Rizhao City, China in 2020 and 2021. The effects of nitrogen application levels (N: 0 kg·hm−2, CK; N: 45 kg·hm−2, U1; 75 kg·hm−2, U2; and 105 kg·hm−2, U3) and nitrogen application forms (ammonium bicarbonate, AB; ammonium bicarbonate + urea, UAB; and urea, U) on soil moisture, as well as nitrogen spatiotemporal change, and autumn tea yield and quality, were studied. Results showed that applying ammonium bicarbonate or urea through a drip irrigation system can significantly increase the tea plant evapotranspiration and the autumn tea yield and quality (including free amino acids and tea polyphenols). With the same nitrogen application, the urea fertilization treatment had the higher ammonium nitrogen content within the 0–60 cm soil layer. The application form of nitrogen fertilizer had a significant impact on the yield of autumn tea, and the yield increasing ability was U > UAB > AB. The partial factor productivity of applied nitrogen under the AB treatment was the lowest. The yield-increasing effect of nitrogen fertilizer can be observed only 16–18 days after topdressing through the drip irrigation system. In 2020 and 2021, the yield of autumn tea under the U3 treatment increased by 40.6% and 23.0%, respectively, compared with the CK treatment. In conclusion, the topdressing with urea 105 kg·hm−2 with drip irrigation for tea plants in autumn is recommended. This recommendation will provide a theoretical basis for efficient irrigation and yield increase in tea gardens.