Ecofallow: More crop per drop with paraquat

Weeds can rob water stored in fallowNon-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 such as paraquat are essential to the efficient conservation of water for use by crops in dry regions. Low rainfall during the growing season means that in these regions crops rely mainly on stored soil moisture.
Ecofallow is a system of soil management developed in the dry mid- and western states of the US and Canada to conserve moisture throughout the crop rotation. The ecofallow system (also known as ‘chem fallow’) is based on no-till

Description

Also known as conservation tillage or zero tillage is a way of growing crops from year to year without disturbing the soil through tillage ie cultivating the soil usually with tractor-drawn implements.

Authoritative On-line References and Resources

No-till.com:  A portal for on-line information about no-till farming.
cultivation and herbicides to ensure weeds do not deplete the reserves of soil moisture being accumulated during the fallow (uncropped) period between crops.1,2

Crops are thirsty

As a general rule, one litre of water has been used to produce one calorie of food. Considering average requirements for adults are 2000 – 3000 calories per day, this fact emphasises the importance of water to food security. In regions where rainfall is low and irrigation is not feasible, crop yields are restricted by insufficient water. In semi-arid regions, leaving fields fallow between crops is a means of accumulating water stored in the soil, ie usually winter rainfall. This provides more water for the following crop and has a very strong relationship with higher yields. Research in these situations has found that the yield of wheat can triple from doubling soil water reserves.2

Ecofallow

Ecofallow conserves water by:

  • Holding snow
  • Reducing water run-off

    Description

    The occurrence of surplus liquid (like rain) which originates up-slope and is collected beyond the ability of the soil to absorb it. The surplus liquid then flows away over the surface to reach the nearest surface water (pond, lake, river).

    Authoritative On-line References and Resources

    US Geological Survey's Water Science School
  • Increasing water infiltration
  • Reducing soil temperature
  • Reducing evaporation
and reduces 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.
by wind and rain
Ecofallow crop rotations typically comprise winter wheat and a row crop

Description

Annual crops traditionally grown in wide rows such as corn, soybeans and cotton.

Authoritative On-line References and Resources

The US national associations for those involved in the production of, and trade in, corn, soybeans and cotton:  http://www.ncga.com http://www.soygrowers.com http://www.cotton.org 
such as maize, grain sorghum, proso millet or soybeans, interspersed by fallow periods spanning the winter seasons.
In the US Great Plains states such as Nebraska, a shorter fallow follows wheat harvest in July until planting a row crop in May; and a longer one lasts from row crop harvest in September or October through to planting winter wheat the following September.3 Ecofallow is designed to trap and retain as much rainfall and snow as possible so as to build-up soil water reserves. The stubble holds snow and spread straw and chaff retained on the soil surface prevent capping and insulate the soil, increasing water infiltration and slowing evaporation. However, it has been found that only 10-15% of rainfall during the fallow may be stored through to the next season because of use by weeds and evaporation when fallow fields are tilled to control them.1,2 Figure 1. Water consumption by weeds and crops (litres/kg). (Croissant et al, 2008)By their nature, weed species are competitive and roots may develop faster and reach deeper than crop roots. Some species use much more water than crops (Fig. 1.). The amount of water used by an infestation of Chenopodium album, if conserved through adequate weed control practices, could enable yield increases of 2.5 tonnes per hectare (1.0 ton/acre) in maize and 3 tonnes/hectare (1.2 tons/acre) in wheat. 4 Establishing no-till cultivation practices in which weeds are controlled by herbicides is the key to a successful ecofallow system. Research in Nebraska and Colorado has shown that the amount of stored water can increase between 40% and 60% in no-till fields over conventionally tilled ones when weeds are successfully controlled.5

Weed control

Crops should be cut as high as possible to leave a long stubble. This not only traps snow better, but also avoids cutting weeds too short. Paraquat is a contact herbicide and a better kill will be obtained sooner when weeds already having a good leaf area are sprayed soon after harvest. Slow autumn growth or rainfall soon after application are not problems for paraquat, unlike for systemic herbicides. If perennial or large annual 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.
are present results may be improved by tank-mixing with dicamba or 2,4-D ester. In some situations better weed control can be achieved by tank-mixing with a photosystem II inhibitor like metribuzin for enhanced burndown or atrazine to add residual weed control.
Using herbicides with different modes of action is important to fight the evolution of resistant weeds.  In fallowed fields without crop competition the threat of resistance is particularly severe. In these parts of the US and Canada resistant weeds are already widespread, including glyphosate resistant Amaranthus tuberculatus, Ambrosia trifida and Kochia scoparia.6  In Brazil paraquat is regarded as an essential complement to glyphosate to help avoid the evolution of glyphosate resistant weeds. Although around 70% of fresh water extraction is used for agriculture, there is increasing demand from other sectors, as well as the impact of climate change on supplies. This means that more reliance will have to be put on rainfed cropping systems and the conservation of water through approaches such as ecofallow.

References

  1. Doupnik, B and Boosalis, M G (1980). Ecofallow- a reduced tillage system – and plant diseases. Plant Disease, January 1980, 31 – 35.
  2. Hatfield, J L et al (2001). Managing soils to achieve greater water use efficiency: a review. Agronomy Journal, 93, 271-280
  3. Klein, R N (2012). Ecofarming. University of Nebraska Lincoln Extension, NebGuide G551. 
  4. Parker, R (2003).  Drought advisory bulletin EM4856.  Washington State University Cooperative Extension. 
  5. Croissant, R L, et al (2008). Dryland cropping systems. Colorado State University Extension. Fact sheet 0.516
  6. International Survey of Herbicide Resistant Weeds

Notes

The brand name of the leading paraquat product is Gramoxone.