Developing no-till maize in China with paraquat

Controlling weeds the hard wayFarmers in southwest China are adopting no-till


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.

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maize production using paraquat for weed control. A large proportion of crops in the region are grown by smallholder farmers on hillside fields. Soil erosion


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.

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and loss of fertility are serious problems. The traditional methods of hand and mechanical weed control have very high labor demands and often cannot be done in a timely manner to achieve the best yields.
Recognizing these issues, a project was set-up to teach farmers and extension workers how to grow no-till maize. Demonstration field trials and training sessions were used to show how using paraquat in a no-till system could improve crop productivity, soil fertility and rural livelihoods.

Maize in China

Production of major crops in China (FAO, 2009)While the production of rice and wheat in China has been fairly stable over the past 15 years (see chart) that of maize has increased by around 50%1. In 2009, the area of maize harvested overtook rice for the first time. Over 31 million ha of maize were harvested compared to just less than 30 million ha of rice. One of the main reasons behind the rise of the maize crop is China’s increasing consumption of meat. Maize provides feed for poultry and livestock. In southwest China it is common to find farmers growing three crops each year in mainly rainfed cropping systems2. A common rotation is winter wheat, followed by summer maize, then vegetables being grown in the fall. The major staple crops besides maize are rice and wheat, but a huge variety of other crops are grown. These include soybeans, peanuts, oilseed rape, potatoes, sweet potatoes, bamboo, cassava, watermelons, peppers and tea. Many farmers intercrop to increase food production. For example, maize seedlings are transplanted between the rows of growing wheat crops. The maize plants have generally started to elongate by the time the wheat is harvested, saving many weeks of growing time. However, this practice requires a lot of labor and increases costs. Introducing modern technology can bring significant benefits to farming in the region. Yields from local maize varieties are typically in the range 1.5 – 2.3 tonnes/hectare. However, if modern hybrid varieties are grown the yield range is 3.8 – 5.3 tonnes/ha with yields as high as 7.5 tonnes/hectare achievable with the best agronomic practices2. Distribution of labor used in growing a maize crop to harvest (Meng, 2006)In surveys sponsored by CIMMYT (The International Maize and Wheat Improvement Center)2, farmers in villages in the southwest were asked why they thought that their yields were less than those potentially achievable. The main reasons were believed to be problems of drought, soil erosion and decreasing fertility, and the inability to weed in good time. Land preparation, inter-row tillage and hand weeding account for large proportions of the labor inputs into maize growing (see chart), making them important targets for any improvements in efficiency.

Paraquat no-till project

Adopting a no-till system in which fields are not plowed before a crop is planted can address problems like those facing smallholder farmers in the uplands of southwest China. The role of paraquat in no-till is to control weeds that would otherwise be buried by plowing or uprooted by soil cultivations. Its fast action allows crops to be planted immediately, saving time over the main alternative, glyphosate, which is slow acting. A demonstration and training project was set-up in Yunnan, Guizhou and Guangxi provinces. In field trials, conventional methods of maize production were compared to no-till in which paraquat was sprayed to burndown weeds before planting, either alone or in mixture with the soil residual herbicide S-metolachlor. In the no-till plots, instead of hand weeding as usual, paraquat was sprayed between the rows once the maize had reached the 6-8 leaf stage and was at least 15 cm taller than the weeds. A simple nozzle shield can be used, but unlike glyphosate, a few drops of paraquat spray on the crop leaves cause little damage because the effect is contact only with no systemic action to affect the growing points. Paraquat has controlled all inter-row weedsA better way of weeding with paraquat                   No-till using paraquat greatly reduces the workload involved in land preparation and weeding. This results in lower costs for labor and fuel where some mechanisation is involved. Fewer animals are needed to draw cultivation implements. The opportunities for more timely field operations gives the potential for higher yields and increased revenues. The demonstation trials showed a substantial yield advantage in favor of no-till. The main reason behind this was the greater water holding capacity of the unplowed soil, particularly important in the very dry summer, which enabled the crop to establish well. No-till systems also improve soil fertility while protecting the environment. Soil erosion is reduced and both the drainage and water holding capacity of the soil are improved. Not disturbing the soil by cultivations increases biodiversity


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

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by creating and preserving habitats, and increases soil organic matter. This, in turn, reduces emissions of carbon dioxide.
Farmers were invited to see the   demonstration trials and learn about the   benefits of adopting no-till.Finally, rural communities benefit from less time needing to be spent in the fields. Under current practices, much of the heavy field work is done by women2. A no-till cropping system using paraquat allows not only better timeliness of field operations, but also more time to be spent on other activities off the farm. No-till using paraquat for weed control will allow more efficient maize production in China, while improving the soil and reducing the environmental and social impact of farming.


  1. FAO crop statistics
  2. Meng, E C H (2006). Maize in China: Production systems, constraints and research priorities. Mexico, D F: CIMMYT.


The brand name for the leading paraquat product is Gramoxone.