Rice: key to food security for billions

Rice is the staple food for more than half the world. In Asia alone, more than two billion people obtain over 60% of their calories from rice. In developing countries nearly one billion people find employment associated with rice in the food chain. It is the most rapidly growing source of food in Africa and is critical to food security.

Protecting rice from weeds, pests and diseases is essential to avoiding heavy losses in yield. Weed control is usually most important. Paraquat is used to prepare the land for cultivating rice and on the bunds (levies) which surround paddy fields to retain the flood water. The traditional way of preparing paddy fields, still used by tens of millions of farmers, is to plow and cultivate several times. This is time consuming, costly and labor intensive.

As a 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. herbicide, paraquat allowed the development of no-tillDescription 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 http://www.no-till.com/index.htm A portal for on-line information about no-till farming. systems. No-till does not rely on plowing to control weeds. Not disturbing the soil helps prevent erosion and maintains a healthy soil. It is also important in climate change. No-till significantly reduces the production of methane, a greenhouse gas more damaging than carbon dioxide. When fields are plowed before flooding, buried weeds and stubble decay in anaerobic conditions to release methane.

Some weeds have evolved biotypes which are resistant to glyphosate, the main alternative non-selective herbicide. Using paraquat, with its distinctive mode of action, is helping to avoid problems of weed shiftsDescription A change in the weed community within a field i.e. relative abundance or type of weeds. This can be the result of a management practice like herbicide use or any other phenomenon that brings about a change in weed species composition. Species or biotypes adapted to current weed management practices increase, whereas weeds susceptible to those practices decrease. Authoritative On-line References and Resources http://www.weeds.iastate.edu/mgmt/qtr00-1/popdyn.htm A classic article on weed population dynamics on the Iowa State University Weed Science website. and resistanceDescription The inherited ability of a plant/weed to survive a dose of a herbicide normally lethal to that species. Authoritative On-line References and Resources http://www.weedscience.org/in.asp The International Survey of Herbicide Resistant Weeds monitors the evolution of resistant species and assesses their impact. All confirmed instances of new cases are listed..