Benefits on the farm
Paraquat is an important tool for weed management. It controls many species and can be used with most crops. Its mode of action means that it is especially valuable where intensive use of glyphosate has caused, or threatens to cause, the development of glyphosate resistant weeds.
The extensive adoption of glyphosate tolerant GM crops has led to farmers over-relying on glyphosate.
Although glyphosate is encouraging the continued adoption of no-till, with all the benefits to soil conservation that brings, up to three million hectares in Brazil are now estimated to be infested with glyphosate resistant weeds.
However, an integrated weed control system involves continuing to spray glyphosate for burndown, but following just before or just after planting the crop with an application of a paraquat-based herbicide.
Paraquat acts fast in all seasons, no matter what the conditions: hot, dry, wet, early season or late. Paraquat is rainfast in 15 - 30 minutes.
In West Bengal, India, using paraquat to burndown weeds in a no-till system means farmers can transplant a new rice crop after only four days compared to the usual 12 days. Traditionally, fields are plowed and farmers have to wait for buried weeds to decompose sufficiently to allow a final cultivation.
Symptoms of paraquat action appear quickly, especially on hot sunny days, and soon weed shoots are completely desiccated.
Time saved is valuable even in the following vegetable crops because earlier planting means earlier harvest and better prices.
Safe to crops
Paraquat kills weeds precisely providing excellent inter-row weed control without damaging crops. Accidental spray onto crop leaves will not damage the whole plant.
Crop safety is especially important while controlling weeds in bananas because the next harvest cycle depends on a new crop of daughter suckers. These are very susceptible to being killed by systemic broad-spectrum herbicides based on glyphosate.
Paraquat can be used safely around parent and daughter plants with no fear of accidental spray drift damaging either generation.
Once sprayed, paraquat kills the weeds and then becomes inactive in the soil – this allows rapid turnaround and planting of another crop.
Vegetable farmers of Guandong province, China, use paraquat to grow up to eight crops each year on the same land. After spraying, weeds are killed within one or two days and during this period the land can be prepared for the next crop without delay.
Because paraquat is completely inactivated upon contact with soil, the crop can be sown or planted safely as soon as the soil is ready.
With systemic herbicides, farmers would have to wait for 10 days after spraying before beginning work on the next crop. With eight crops per year, this would represent a loss of 80 days of crop production.
Protects soil fertility
Using paraquat in conservation tillage programs dramatically reduces soil erosion – this safeguards soil fertility.
Non-selectiveDescription A chemical product used for eliminating all types of weeds (annual and perennial grasses and broadleaved weeds). Authoritative On-line References and Resources http://www.weeds.iastate.edu/ An invaluable source of contemporary information about herbicides and weeds from Iowa State University. herbicides are essential components of conservation tillage because fields are not plowed to bury weeds, and desiccated vegetation, stover and stubble provide a protective cover to the soil. This helps to minimise erosion, provides habitats for beneficial insects and other wildlife, and undisturbed soil builds higher levels of organic matter, key to good soil structure and fertility.
However, weed species have developed resistance to glyphosate and in some areas are causing farmers to return to plowing. Paraquat provides an alternative for conservation tillage systems.
Controlling weeds reduces competition with crops for space, water, light and nutrients. This means better quality, clean crops and higher yields.
Farmers in the mountains of Vietnam can plant maize crops more than two weeks early by using paraquat in a conservation tillage system.
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 show that using paraquat for weed control increased maize yields by more than 50%.
Early planting was crucial to good yields – land preparation with slower acting glyphosate herbicide resulted in much lower yields.
Plowing and handweeding are time consuming and costly operations. Usng paraquat means tillage can be reduced, ideally using no-till where possible, and labor requirements are much less.
In Vietnam, comparisons have been made between traditional cultivation methods and reduced tillage systems using paraquat for weed control. Paraquat was used before planting and later between the crop rows.
Considerably less labor was needed for the maize crop using the paraquat-based system.as shown in the table. As labor is the major input to crop production this reduced overall costs and boosted profits.
| Production Costs
| Profit (Loss)
Paraquat used in conjunction with no-till crop establishment can reduce fuel use by more than 30 litres/ha compared to intensive tillage – this reduces carbon emissions and saves the farmer money.
A breakdown of fuel use in Illinois, USA, showed that, although some gains from lower fuel use under no-till are clawed-back by more fuel used to plant and spray, no-tilling corn used 14% less fuel, and no-tilling soybeans used 49% less.
The USDA 2007 Farm Bill Theme Paper ‘Energy and Agriculture’ stated:
“During the past couple of decades, … farmers [have] adopt[ed] no-till practices on about 25 million hectares. Assuming average savings of 33.13 liters/ha (3.5 gallons per acre) in diesel fuel, this amounts to a savings of 821 million liters of diesel fuel per year with cost savings to farmers of about $500 million per year.”