Re-utilization of factory tea waste as a potential biostimulant on the early growth and nutrient uptake of tea (Camellia sinensis (L.) O. Kuntze) nursery plants

Humic-like substances extracted from organic waste materials are widely used as plant biostimulants in sustainable agriculture. This study was aimed to extract two types of humic-like fractions from tea waste and study their chemical characteristics and investigate their biostimulant effects on the early growth of tea nursery plants under different application methods and fertilizer rates. Humic-like fractions were extracted from tea waste using alkaline hydrolysis. One fraction has purified humic acid named as humic-like acid (HLA) while the other has impurified humic and fulvic acids called as humic-like substances (HLS). Both fractions were applied as foliar and soil application along with full (100%) and half (50%) rates of fertilizer. The results revealed that HLA had higher total organic carbon and elemental composition, while HLS showed higher humic yield, C/N ratio, total acidity and E4/E6 ratio. The results of the plant study indicated that foliar application HLS with full rate of fertilizer significantly improved the dry weight of various plant parts (Leaf, stem and root), growth parameters, and nutrient uptake compared to untreated plants. Foliar application of HLS and HLA along with 100% fertilizer increased the total plant biomass by 36.9% and 22.6% respectively over control. Furthermore, both fractions increased the concentrations of leaf N and P and the uptake of N, P and K. Our findings revealed that foliar application of HLS along with 100% fertilizer could be used to produce vigorous tea nursery plants most suitable for successful transplanting in the field.