Vol.:(0123456789) 1 3 International Journal of Environmental Science and Technology https://doi.org/10.1007/s13762-018-1791-y ORIGINAL PAPER Humic substrates extracted by recycling factory tea waste improved soil properties and tea productivity: an innovative approach P. Pramanik 1  · S. Safque 1  · A. Jahan 1 Received: 31 July 2017 / Revised: 30 November 2017 / Accepted: 14 May 2018 © Islamic Azad University (IAU) 2018 Abstract Factory tea waste is a high lignin and phenolic compounds-containing fbrous material generated in tonnes in tea manufactur- ing factories. In spite of its high nitrogen content, these physical and chemical properties limit its application as an organic amendment in soil. In this study, a novel technique was developed for extracting humic substrates by recycling factory tea waste and potential of those extracted humic substrates for improving soil properties and tea productivity was evaluated under feld condition. Humic substrates are organic soil amendment that is often used for enhancing chemical and biochemical properties in soil. For extracting humic substrates, factory tea waste was processed through multi-step technique combined with easily available plant biomass like aquatic weeds. The method was suitable for extracting up to 25–30 L humic substrate solution containing 25.1 ± 3.8 g L −1 active constituent, 507.3 ± 11.8 mg L −1 total nitrogen and 2.91 ± 0.07 g L −1 total potas- sium by recycling each kilogram factory tea waste. The extract had shown fair similarity with standard humic acids. Under feld condition, extracted humic substrates lead up to 6% increase in tea productivity and improved soil chemical properties. The residue remained at the end of this process was further vermicomposted to prepare organic amendment having total nitrogen content 1.34 ± 0.07 mg g −1 with C/N ratio 10.87 ± 0.92. In this study, the addition of pond sediment produced inferior quality humic substrate and vermicompost. Keywords Factory tea waste · Recycling · Humic substrates · Field study · Tea productivity · Fourier transform infrared spectroscopy Introduction Humic substances (HS) are the most stable form of soil organic matter and are considered as a key component of the terrestrial ecosystem. Humic substrates are responsible for many complex chemical reactions in soil (Batjes 1996). These HS contain heterogeneous high molecular weight organic materials, which are resistant to microbial degrada- tion and ubiquitous in the terrestrial environment (McKnight et al. 1990). Humic substrates possess aliphatic and aromatic (phenolic) hydroxyl group and carboxylic groups as the major functional groups (Pramanik and Kim 2014). Since HS form the stable organic C pool in soil; they also control several microorganism-mediated biochemical properties in soil (Tandon 2010). Pramanik et al. (2017) revealed that the application of humic substrates in diluted form enhanced nutrient uptake by tea bushes. Lovely et al. (1996) observed that soil microorganisms often use HS as electron acceptor in redox reactions during their metabolism and application of HS in arable soil enhanced the activity of soil microorgan- isms and the growth of plants (Suarez-Estrella et al. 2008). They extracted HS from composted organic substrates for feld trial. However, that method has a major faw. Com- posting is an easy recycling technique of organic wastes to produce nutrient-enriched organic amendments. During this mineralization, one part of organic carbon (C) in the decom- posing substrates gets polymerized to form high molecu- lar weight stable HS (Silva et al. 2016) and those humi- fed compounds control biochemical properties in compost (Pramanik et al. 2007). The average HS content in composts Editorial responsibility: Necip Atar. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13762-018-1791-y) contains supplementary material, which is available to authorized users. * P. Pramanik prabhat2003@gmail.com 1 Soils Department, Tocklai Tea Research Institute, Tea Research Association, Jorhat, Assam 785008, India