Diversity and behaviour of the naturally regenerated vegetation in commercial tea soils under herbicide free integrated weed management

Abstract

Weed management is essential in agriculture to prevent Economic Crop Damage in farm products due to quality and quantity losses. Herbicides are profusely being used to meet this objective despite their hazardous nature on human health and the environment caused by residual contamination of food and drinking water. Sri Lanka imported 7,967,852 kg and 5,675,611kg of Herbicide chemicals in the forms of bulk and ready to use formulations in year 2013 and 2014 respectively and Commercial Tea Plantations too are heavily depend on herbicides to maintain “Clean and Clear Ground Concept” (CCGC) based mind set established in the sector. However, CCGC is not recommended by Tea Research Institute of Sri Lanka due to severe degradation in the tea soils resulted. Many of the so called weed species has the ability to thrive in degraded poor soils forming a quick ground cover arresting further depletion in soil and upgrade same by addition of Organic Carbon as leaf litter and root secretions feeding soil microbes. This study explored the diversity and perennial behaviour of the Natural Vegetative Regeneration (NVR) in Commercial Tea Soil under herbicide-Free Conditions to demonstrate the possibility of practicing Herbicide-Free Integrated Weed Management (HFIWM) in the Tea Industry at commercial scale in Sri Lankan conditions. The survey commenced in Hapugastenne estate Maskeliya Plantations PLC., following to pruning, on a weed free, exposed Tea field in an extent of one hectare, where natural regeneration of vegetation was allowed and monitored, under a Treatment of “Herbicide - Free Integrated Weed Management” (HFIWM), for three years. Non-IWM (Control) area of similar extent was demarcated adjoining to said area and sprayed with Diuron, Paraquat and Glyphosate, as recommended by the Tea Research Institute of Sri Lanka. The naturally regenerated Terrestrial Vegetation in treated and control areas, was surveyed periodically and simultaneously, by investigating 3m X 3m sample plots with four replicates each time, concerning species diversity and recorded the variations observed. Non-IWM section displayed a continuous increase in plant diversity up to 76 species, within three years, dominated by Herbicide tolerant weed species. Vegetation established on HFIWM area reached a peak of 64 plant species within the first year itself, forming a complete ground cover whilst effectively suppressing many of the targeted notorious weeds which cause severe economic damage in Commercial Tea Plantations.