Focus on Argentina

No-till soybeans: a common sight in the fields of ArgentinaFarming is vital to Argentina’s economy and Argentinean farmers have always been eager to adopt new technologies. Grains, food and feed commodities such as flour, oil and cake accounted for almost 40% of Argentina’s exports in 2011, which were worth $84 billion in total.1 Soybeans made by far the greatest contribution (beans $5.5 billion; cake $10 billion; oil 5.2 billion). Soybean has become by far the most important crop and nearly all fields are planted with GM varieties, with the majority being grown under no-till. This article focuses on crop production in Argentina and the key role of non-selective

Description

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 like paraquat.

Cropping

Figure 1.  Harvested areas of soybeans and maize in Argentina (FAOSTAT).The area of soybeans cultivated in Argentina has grown dramatically to become the country’s most important crop by far.2 Around 20 million ha were grown in 2013. Maize was the next most widely grown crop at 4.5 million ha (Figure 1). Other major crops are wheat (3.1 million ha), sunflower (1.2 million ha) and barley (1.2 million ha). Each of these three crops has approximately halved in area since 2000 as the soybean area has expanded. Typical crop rotations involve longer and shorter season crops and sometimes double cropping or periods of fallow.3,4 Soybeans are planted from October through January, with the latest sown crops being planted as a second crop following cereals. Harvest is from March to June. Wheat may then be planted and is harvested in December. Fallowing is used to conserve moisture and instead of being cropped fields may lie fallow until maize is planted in September through January for harvest in March to June Argentina’s farmers were the first in the world to grow GM crops. Glyphosate tolerant soybeans were first planted in 1996 and within seven seasons more than 90% of the country’s soybean crop was down to GM varieties.5 This technology has made weed control considerably easier, but problems with glyphosate resistant weeds began to occur after about ten years.

Glyphosate resistant weeds

Glyphosate resistant weeds are now widespread in Argentina, especially in crops of cereals, maize and soybeans (Table 1).6 Populations resistant to ALS inhibitors (e.g. sulfonylureas, imidazolinones) and ACC-ase inhibitors (e.g. aryoxyphenoxypropionates, cyclohexandiones) are also present. Table 1. Weed species with confirmed glyphosate resistant populations in Argentina
Weed species Original cropping situation Year first confirmed
 Digitaria insularis *  Soybeans, maize  2014
 Urochloa panicoides *  Soybeans  2013
 Brassica napus *  Cereals  2013
 Amaranthus quintensis  Soybeans  2013
 Eleusine indica  Fallow, soybeans  2012
 Echinochloa colona  Maize, soybeans  2009
 Cynodon hirsutus  Soybeans  2008
 Lolium perenne  Wheat, barley, soybeans  2008
 Lolium multiflorum  Wheat, barley  2007
 Sorghum halepense  Soybeans  2005
* Resistant populations recognised by Argentina’s ministry of agriculture When growing glyphosate tolerant GM crops, farmers must avoid the temptation to rely too heavily on glyphosate. Using a variety of methods for weed control, including herbicides with different modes of action, occasional soil cultivations and cultural practices such as crop rotation are vital to contain, and ideally to prevent, the occurrence of herbicide resistant weeds. With its distinctive mode of action, paraquat has an important role to play here. No weeds resistant to paraquat have been recorded in Argentina or in any country in South America.6

No-till

Another major technological advance in Argentinean crop production has been the widespread adoption of no-till.7,8 Argentina ranks alongside Brazil and the US as the countries with the largest areas of no-till. In terms of the percentage of cropped land under no-till, Argentina leads by a considerable margin with at least two-thirds of arable crops grown in fields that are never cultivated.

No-till in Argentina

  • 90% less soil erosion

    Description

    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

    http://soilerosion.net/ 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.
  • 1 litre diesel in plowed fields = 50 kg grain
  • 1 litre diesel in no-till = 123 kg grain
  • 135 mg organic N/100 g soil before no-till
  • 260 mg organic N/100 g soil after 10 years of no-till
AAPRESID, the Argentinean association of no-till farmers promotes and researches no-til
production in Argentina. Some results of its research are shown in the box opposite.
Practices such as rotating the direction of sowing by 30o for each crop mean that root growth is spread more evenly over fields. Cover crops

Description

Cover crops are primarily planted not to be harvested for food but to reduce soil erosion, control weeds and improve soil quality. They are usually plowed or tilled under before the next food crop is planted, in which cases the "cover crop" is used as a soil amendment and is synonymous with "green manure crop."

Authoritative On-line References and Resources

http://attra.ncat.org/attra-pub/covercrop.html ATTRA is the US National Centre for Appropriate Technology's Sustainable Agriculture Information Centre.
are often sown to protect the soil from erosion and to conserve moisture between crops. Popular species are oats (Avena sativa), the legume hairy vetch (Vicia villosa) and teff grass (Eragrostis tef). These have to be killed using a non-selective herbicide before planting the following crop into the residue.

Weed control with paraquat

Paraquat’s versatility means that it can be used to prepare arable and vegetable fields for weed-free planting; or after sowing but before crop emergence (especially suitable for some vegetables that take longer to emerge). It can also be used post-emergence in dormant alfalfa after cutting where is it us particularly recommended to suppress the perennial grass Stypa brachychaeta. Weeds in orchards, vineyards and sugarcane can be controlled thanks to paraquat. Paraquat is most effective when used to control weeds up to two weeks after emergence. Symptoms may appear just a few hours after spraying and weeds may be fully desiccated within a day or two if the weather is warm and sunny. Under cool and cloudy conditions, paraquat is rather slower acting, but can give a more thorough kill. It has the important property of being rainfast after only 15 – 30 minutes. Application rates are in the range 300 – 600 g/ha. Higher rates are recommended for denser weed stands. Lower rates may be used as a second application to control regrowth or new flushes of emergence. Weed control can be enhanced and extended by tank-mixing hormone and residual herbicides. Before planting maize, adding 2-4, D will improve the control of broadleaved weeds

Description

The leaves are "broad" as opposed to the "narrow" leaves of grasses. Also called 'dicots' having two seed leaves, while grasses are 'monocots' having one seed leaf.

Authoritative On-line References and Resources

http://www.iwss.info The International Weed Science Society.
such as thistles and crucifers, while adding atrazine will give residual control of new germination.
Chemical fallow is a valuable technique to conserve water with a break in the rotation before planting crops such as maize, soybeans and wheat. Paraquat is the ideal herbicide to quickly kill weeds in fallow and stop them wasting valuable moisture. In the autumn of the fallow before planting soybeans or wheat, mixture partners including metsulfuron-methyl, dicamba and diuron can be added to paraquat to improve the control of difficult broadleaved weeds. Only diuron can be used as a burndown partner before planting the following crop of soybeans. Diuron enhances the activity of paraquat because it gives a slight delay to the onset of the herbicidal effect, allowing some movement of paraquat in the weeds and a more thorough kill. Other articles focusing on the benefits of using paraquat in South America can be found here.

References

  1. World Bank Country Profile on Argentina (2011)
  2. FAOSTAT
  3. Farmers Weekly, S. Africa (2014). Doing the tango with no-till in Argentina
  4. Farmers Weekly, S. Africa (2014). Grass roots no-till in Argentina
  5. Finger, R, et al (2009). Adoption patterns of herbicide tolerant soybeans in Argentina. AgBioForum, 12,(3&4), 404-411
  6. International Survey of Herbicide Resistant Weeds
  7. AAPRESID (La Asociación Argentina de Productores en Siembra Directa)
  8. Derpsch, R, et al (2010). Current status of adoption of no-till farming in the world and some of its main benefits. International Journal of Agricultural and Biological Engineering, 3, (1), 1-26

Notes

The brand name of the leading paraquat product in Argentina is Gramoxone Super. The brand name of a mixed formulation of paraquat and diuron is Cerillo.