Soil nitrogen and tea leaf properties in organic and conventional farming systems under humid sub-tropical conditions

Abstract

The effects of organic (OFS) and conventional (CFS) farming systems on soil nitrogen and tea (Camellia sinensis L.) leaf physiological as well as biochemical properties under humid sub-tropical conditions were studied at the experimental field of Tocklai Tea Research Institute, Jorhat, Assam, India. A part of the field under CFS was converted to organic in 2008 by using different organic manures, viz., vermicompost, P-enriched vermicompost, de-oiled neem cake, and inserting green crop, besides phosphorous (P) and potassium (K) solubilizing bacteria. After 4 years of conversion process, OFS resulted in significantly higher values for leaf total catechin (262.03 mg g−1), (−)-epigallocatechin gallate (EGCG, 159.97 mg g−1), and (−)-epicatechin gallate (ECG, 42.93 mg g−1) contents although there was up to 22 % reduction in tea yield. On the other hand, CFS resulted in significantly higher values for soil available nitrogen (154 mg kg−1) contents as well as for leaf chlorophyll a (2.51 mg kg−1), chlorophyll b (1.02 mg kg−1), and total chlorophyll (3.53 mg kg−1), contents. No significant difference was observed for caffeine, (−)-epigallocatechin (EGC), (+)-catechin (C), and (−)-epicatechin (EC) contents between the two farming systems studied. Correlation analysis indicated that (−)-EGCG was the major catechin fraction significantly correlated with leaf chlorophyll a, chlorophyll b, and total chlorophyll contents. The present study has provided knowledge on soil available nitrogen as well as leaf physiological and biochemical contents in tea shoots under humid sub-tropical conditions in Northeast India.