International Year of Soils: Feeding our cities

Fresh food for our citiesThis is the third in a series of articles celebrating the UN FAO’s International Year of Soils and explaining the important role paraquat plays in promoting healthy and productive soils around the world. FAO have developed a Soils Portal designed as a source of soil information. The key messages from FAO are that1:
  • Healthy soils are the basis of healthy food, feed, fibre, fuel and medicines.
  • Soils support biodiversity

    Description

    The variety of life in all its forms, levels and combinations. Includes ecosystem diversity, species diversity, and genetic diversity (IUCN, UNEP and WWF, 1991).

    Authoritative On-line References and Resources

    http://earthtrends.wri.org/ EarthTrends is a comprehensive online database, maintained by the World Resources Institute, that focuses on environmental, social, and economic trends. Statistics on biodiversity indicators are available.
    .
  • Soils help to combat climate change, having key roles in the cycling of carbon and nitrogen.
  • Soils store and filter water, and improve resilience to floods and droughts.
  • Soil is a non-renewable resource, essential for food security and sustainability.
Previous articles have looked at the threat posed by soil degradation and the benefits of no-till farming, and the role of soils and their management in tackling climate change. This article looks at another theme of the International Year of Soils, which is about farming conducted in and around cities, known as urban and peri-urban agriculture or horticulture.

Urban farming

In 2014, the UN estimated that 54% of the global population lived in urban areas.2 The forecast is that by 2050 this figure will reach 66%, with 90% of the increase concentrated in Asia and Africa. In 1990, there were ten ‘mega-cities’ with 10 million inhabitants or more. Currently, there are 28 mega-cities worldwide, lead by Tokyo with 38 million people, followed by Delhi, Shanghai, Mexico City, São Paulo and Mumbai. Urban and peri-urban farming is becoming more important to facilitate and ensure the supply of food to cities, especially fresh vegetables. Surprisingly high productivity can be achieved, but of course, this puts pressure on the soil in terms of maintaining its ability to sustain vigorous and healthy crop growth. However, the availability of land is limited and it is essential to keep precious soil in a good state.

Benefits of paraquat

Using paraquat for weed control in conservation tillage

Description

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.
or no-till systems has many benefits, which address the International Year of Soil’s key messages:
  • More soil organic matter for improved health, structure and fertility, and locking-up carbon dioxide.
  • Crop residues and weed roots remain to stabilize soil and resist erosion.
  • Undisturbed fields after harvest provide habitats to increase biodiversity.
  • Reduced cultivations mean less soil compaction.
  • Paraquat is deactivated immediately on soil contact and does not leach

    Description

    The natural process by which water soluble substances are carried downward through the soil into groundwater.
    .
Paraquat is sprayed to control weeds before vegetable crops are planted or in between the rows, not over the whole crop. Many vegetable crops, e.g. lettuce, brassicas, are often transplanted out into the field, not sown from seed.  Paraquat is immediately and strongly bound to soil, so it cannot be taken-up by plant roots. Therefore, transplants will not be damaged. Paraquat gives complete control of weeds within a day or two even in cold weather, and within hours in hot, sunny weather. Absence of ploughing and fast action can save a lot of time. This means that more crops can be grown each season on the same plot of land, raising productivity. You can read more about how paraquat helps support the growth of cities in the following articles:

Herbicides support city living

As people flood into cities, fewer and fewer remain in the countryside to grow food. Manual weeding is the most intensive operation on small farms in developing countries. Paraquat and other herbicides provide a solution. Read more

Paraquat is deactivated in soil and does not leach

Paraquat is extremely tightly bound to soil particles on contact. This means that it can be used without concern for damaging crops by root uptake and it cannot get into groundwater. Read more

Growing better vegetables in the Philippines

Paraquat is used before vegetables are planted and can be sprayed around crop plants. Weeds are, therefore, controlled at all stages when crops are vulnerable to weed competition and consequent loss of yield. Read more
 

References

  1. FAO International Year of Soils website
  2. United Nations Department of Economic and Social Affairs. 2014 Revision of World Urbanization Prospects.

Notes

The brand name of the leading paraquat product is Gramoxone.