Paraquat supports sustainable tea in Vietnam

Paraquat prevents soil erosion on slopesTea is a thriving crop in Vietnam and farmers rely on paraquat for a weed control system that reduces soil erosion.  Much of the tea crop is grown on sloping land prone to losing very significant amounts of soil each year. Results of research conducted by the Northern Mountainous Agriculture and Forestry Science Institute show that using paraquat for weed control instead of hand hoeing can save huge amounts of soil. Paraquat is more effective than glyphosate because it leaves roots intact to anchor the soil.

Tea in Vietnam

Tea is an important industry in Vietnam with six million people involved in production, processing and exporting1. Tea is a native plant to the country and has been cultivated for thousands of years. The industry has been experiencing a rapid expansion since the mid 1990s. Yields have also improved, more than doubling over this period, and now approach the best in Asia2. Exports of tea are increasing and efforts are being made to improve the international image of Vietnamese tea. Vietnamese black tea is generally used in blends. However, fine quality green teas are produced and drunk by the Vietnamese people. Tea cropping has increased dramatically in Vietnam (FAOSTAT, 2009).Using paraquat reduces soil erosion4                         Some of the key issues facing Vietnam’s tea industry are inconsistent yields and serious soil erosion problems. Tea fields tend to be on steep slopes. High rainfall means that soil erosion can be very serious. Erosion losses approaching 200 tonnes of soil per hectare in a single year have been recorded3. Bare soil without any plant cover is most susceptible. Pressure to grow more food has resulted in excessive soil cultivation which soon damages soil structure by reducing levels of organic matter. Poor soil structure leads to erosion and low fertility. Degraded soils mean poor harvests. Even in perennial crops like tea, hoeing to control weeds loosens the soil and makes it susceptible to erosion.

Paraquat saves soil, labor and costs

Researchers at the Northern Mountainous Agriculture and Forestry Science Institute (NOMAFSI) are developing more sustainable cropping


Management and conservation of the natural resource base and the use of technological and organizational change in a manner that ensures continued agricultural production from the land for present and future generations. Such practices conserve land, water, and plant and animal genetic resources. They are environmentally non-degrading, technically appropriate, economically viable, and socially acceptable. Sustainability rests on the principle that we must meet the needs of the present without compromising the ability of future generations to meet their own needs. Therefore, stewardship of both natural and human resources is of prime importance.

Authoritative On-line References and Resources Information from the USDA's Alternative Agricultural Systems Information Center.
systems aimed at combating soil erosion in particular. A previous article on the Paraquat Information Center looked at the results of work on maize . In this article the focus will be on recently published results from field experiments on tea4. These are summarised in the table below.
  Traditional System Paraquat for weed control
Labor (man-days/year) 170   90
Total production costs/ha (million VND) 10.2 6.12
Cost savings/ha (million VND) -  4.08
NB 1 million VND (Vietnamese dong) = US $48.63, May 2011 The traditional weed control system of hand hoeing needed almost twice as much labor as the paraquat-based system. Consequently, it was much more expensive. Using paraquat saved on average the equivalent of nearly $200/ha. Yields of tea leaves improved too. From May through July, nearly 20% more leaves were picked from plots where paraquat had been used. Apart from the short-term advantage of higher profitability through saving labor, using paraquat gives a long-term advantage by saving soil. The chart above shows that in one season an average of nearly 40 tonnes/ha of soil were eroded from plots managed in the traditional way. However, using paraquat reduced this loss to only 16 tonnes/ha. Paraquat was considerably more effective than glyphosate. This was because, being a contact herbicide, paraquat only kills weed shoots leaving the roots intact to anchor the soil. Perennial weeds


Weeds that return year after year. Some die back in the winter but their roots remain alive and shoots reappear in spring; some don't die back and grow in size and stature the next season.

Authoritative On-line References and Resources

The International Weed Science Society represents individual associations around the world.
may be allowed to re-grow, giving a vegetative cover protecting the soil from the impact of rainfall, before spraying again to contain them.
Weed control based on paraquat is helping to improve the sustainability of Vietnam’s tea industry.


  3. Mai Van Trinh (2007). Soil erosion and nitrogen leaching


    The natural process by which water soluble substances are carried downward through the soil into groundwater.
    in northern Vietnam.
    University of Wageningen, Netherlands.
  4. Nguyen Quang Tin, Ha Dinh Tuan, Le Quoc Doanh and Dao Xuan Cuong (2010). The role of Gramoxone 20SL herbicide in sustainable sloping land cultivation. Vietnamese Journal of Plant Protection, 229, (1), 31 – 36


The brand name for the leading paraquat product is Gramoxone.