Response of tea yield, quality and soil bacterial characteristics to long-term nitrogen fertilization in an eleven-year field experiment

Abstract

Nitrogen (N) fertilization is an important field management practice in tea (Camellia sinensis L.) plantations. Although the supply of N fertilizer plays a vital role in the growth and quality of tea plants, the optimal N application rate and the effects of different N application regimens on tea yield and quality still remain unclear. In this study, we conducted an eleven-year field experiment to investigate the impact of N application on tea yield and quality, as well as soil bacterial characteristics. We found that N fertilization quadratically increased the yield and amino acid (AA) content of tea, but quadratically decreased total polyphenol (TP) content. Increasing N rates resulted in significant changes in soil community characteristics, including decreased diversity, weakened community function and lower community stability. Additionally, higher taxonomic levels and low-abundance taxa were affected most significantly by N fertilization. Based on PERMANOVA results, the variation of bacterial community composition can be largely explained (~50%) by the soil properties of pH, exchangeable magnesium (Exch-Mg), exchangeable potassium (Exch-K) and exchangeable hydrogen (Exch-H). Partial least squares regression (PLSR) and path modeling (PLS-PM) illustrated that N fertilization indirectly affected tea yield and quality mainly by causing changes in soil properties of Exch-Al and pH, respectively. Soil bacterial characteristics, on the other hand, contributed relatively little to the changes in tea yield and quality. Overall, excessive N application had an adverse effect on soil quality, despite mostly positive effects on tea growth and quality. N application rates of 119–285 kg N ha−1 yr−1 were the most optimal for high tea growth and quality. Understanding the response of above- and belowground plant characteristics to N application rates should help to guide field fertilization and achieve a higher N-use efficiency in agricultural systems.