Fast acting paraquat means more maize

Research site in the mountains of VietnamFarmers in the mountains of Vietnam can plant maize crops more than two weeks early by using paraquat in a conservation tillage


Any tillage and planting system that covers 30 percent or more of the soil surface with crop residue after planting to reduce soil erosion by water.

Authoritative On-line References and Resources

Purdue University-based Conservation Technology Information Centre.
system. Timely operations are essential in growing all crops and paraquat’s unprecedented speed of action is often a huge help to farmers up against the weather or looking for earlier harvests to get the best prices.
Results of research conducted by The Northern Mountainous Agriculture and Forestry Science Institute (NOMAFSI) show that using paraquat for weed control increased maize yields by more than 50%1. Early planting was crucial to good yields – land preparation with slow acting glyphosate herbicide resulted in much lower yields. As Vietnam has developed, agriculture has had to intensify to increase food production and to compensate for reductions in labor availability due to the movement of people to cities. Much of the agricultural land in Vietnam is on steep slopes. High rainfall means that the potential for soil erosion


Displacement of solids (soil, mud, rock and other particles) usually by the agents of currents such as, wind, water, or ice by downward or down-slope movement.

Authoritative On-line References and Resources This site brings together reliable information on soil erosion from a wide range of disciplines and sources. It aims to be the definitive internet source for those wishing to find out more about soil loss and soil conservation.
is very high. Soil has been recorded as being lost at rates approaching 200 tonnes per hectare in a single year2. 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.

Farming in Vietnam3

  • 60% of labor force farm or fish
  • 22% GDP from agricultural and forestry
  • 30% of exports are food
  • 75% of land is mountainous
  • 3000 mm rainfall/year in some regions
NOMAFSI, based at Phu Tho, is a member organization of the Vietnamese Academy of Agricultural Sciences. One of its main aims is to research and transfer technologies for 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.
of sloping land to highland farmers. Conservation tillage methods (min-till


Least possible soil disturbance for preparing a seedbed by reducing cultivation and avoiding the use of a plow. It can involve direct drilling, broadcasting into existing stubbles or adopting a strategy of reduced tillage. The main benefits are to reduce tillage energy consumption, to conserve moisture and soil structure, to reduce disturbance of soil organisms and to retain plant cover to minimize erosion.

Authoritative On-line References and Resources

The European Conservation Agriculture Federation (ECAF) promotes best soil management practices based on minimal soil disturbance by reduced tillage.
) using non-selective


A chemical product used for eliminating all types of weeds (annual and perennial grasses and broadleaved weeds).

Authoritative On-line References and Resources An invaluable source of contemporary information about herbicides and weeds from Iowa State University.
herbicides for weed control have been reducing soil erosion and increasing yields.
  The encouraging results of work in maize and tea have been published in the Journal of Vietnamese Agricultural Science and Technology1. NOMAFSI researchers constructed trial plots with concrete bunds to enable the amount of eroded soil to be collected and measured. Results on maize are shown below. Using min-till with paraquat reduced soil erosionUsing min-till with paraquat increased maize yield                               The system using paraquat resulted in much less soil erosion and much higher yields of maize - statistically better than both the usual farmer plow-based system and the min-till system using glyphosate. Paraquat has the big advantage of fast action which allowed maize crops to be planted after only two days while planting was delayed by 10 and 15 days for the glyphosate and traditional systems, respectively. Also, unlike glyphosate, paraquat is not systemic so only destroys weed shoots, allowing slow regeneration of many species to provide a non-competitive ground cover. Bare soil should be avoided to resist the erosive force of rainfall and living root systems give soils structure and stability. Reducing cultivations during land preparation meant that considerably less labor was needed for the maize crop, as shown in the table below. As labor is the major input to crop production this reduced overall costs and boosted profits. Paraquat was especially effective because of the earlier sowing date achieved.  
(man days/ha)
 Production Costs
(million VND/ha)
 Profit (Loss)
(million VND/ha)
Traditional practice 220 15.4 (3.0)
Glyphosate 150 13.0   0.8
Paraquat 140 12.8   6.6
NB Labor costs = VND 40,000/day, maize price VND 5,000/kg
VND = Vietnam Dong. US$1 = VND 18,880 in April 2010
  Benefits from conservation tillage and paraquat were also seen in tea. This system halved labor requirements and resulted in an extra VND 3 million profit per hectare. In summary, NOMAFSI have found that conservation tillage systems using paraquat:
  • Advance sowing date
  • Reduce soil erosion
  • Increase yield
  • Reduce labor requirements
  • Increase profitability


  1. Nguyen Quang Tin, Trinh Duy Nam, Ha Dinh Tuan and Dao Xuan Cuong (2008). The role of Gramoxone 20SL herbicide in sustainable sloping land cultivation. Journal of Vietnamese Agricultural Science and Technology, 4, 83 – 91
  2. 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 Wagenigen, Netherlands.
  3. US Library of Congress country profile


The brand name for the leading paraquat product is Gramoxone