No-till is a way of growing crops without plowing. There is no soil disturbance and fields retain a good cover of living or decaying plant material throughout the year. This protects against erosion and encourages a healthy, well-structured soil for growing crops.  The system is also known as zero-tillage or direct drilling and is one of a number of crop production practices that are included in the overall concept of conservation tillage.
There are many benefits that result from creating and maintaining a healthy soil. The global demand for food is forecast to double by 2050 and many more people will want to eat meat. Food energy in beef, for example, requires up to eight times more cropland than an equivalent vegetarian diet. So, more than ever, the pressure is on to increase agricultural productivity and to use land wisely. Protecting the soil is essential for sustainable agricultural production.
Weed control is a fundamental issue in no-till because weeds are not buried by plowing.
No-till is a way of growing crops without plowing. There is no soil disturbance and fields retain a good cover of living or decaying plant material throughout the year. This protects against erosion and encourages a healthy, well-structured soil for growing crops. The system is also known as zero-tillage or direct drilling and is one of a number of practices that are included in the overall concept of conservation tillage.
No-till soils retain water better, while allowing any excess to drain away thanks to a better structure and numerous worm channels making crops more resistant to drought and less likely to become water-logged. Farmers practising no-till spend less on machinery and fuel, and make greater profits. Fewer passes across fields by lighter tractors results in lower emissions of carbon dioxide, and unlike when plowed, no-till soils sequester carbon because of the accumulation of organic matter. Biodiversity above and below the ground also improves. Weed control is a fundamental issue in no-till because weeds are not buried by plowing. Although various weed control practices are used in no-till, including the use of cover crops, non-selective herbicides such as paraquat play a key role in an integrated approach to weed management.
Farmers in southwest China are adopting no-till 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 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
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.
Paraquat has always played a pivotal role in the development of no-till cropping systems in Brazil, as elsewhere. Not only has no-till helped to propel Brazil to the status of an agricultural ‘superpower’, but it has also brought many sustainable benefits by improving soils and reducing erosion, increasing biodiversity, reducing energy use and improving profitability. More recently, the contribution no-till farming can make to fighting climate change has been recognized. No-till soils sequester carbon as organic matter and because there are fewer passes over a field by machinery, considerably less fuel is used.
Brazil’s ABC Program
Plans to increase the area of no-till farming feature strongly in the Brazilian Ministry of Agriculture's ABC program (Agricultura de Baixo Carbono) launched in 2010 to target reductions in greenhouse gas emissions1. Over $1 billion worth of credit will be available to farmers to support the implementation of various approaches to reduce the impact of agriculture on climate change. The goal is to slash more than 160 million tonnes from carbon dioxide equivalent emissions per annum by 2020.
Biodiversity is being encouraged by the adoption of conservation tillage practices, especially no-till farming. Spraying with a non-selective herbicide like paraquat means that weeds can be controlled without the need to plow.
Birds, in particular, are benefiting when fields are not plowed or only lightly cultivated in conservation tillage systems. Leaving stubble and chaff from the previous crop on the soil surface, and undisturbed no-till soil, provides habitats for invertebrates and small wildlife. Whether bird species feed on spilled grain and weed seeds, insects or small mammals, greater numbers are often evident.
One bird species now thriving in no-till fields in the intensive soybean growing areas to the north and south of Sao Paulo in Brazil is the burrowing owl (Athene cunicularia).
Found throughout much of North and South America, as their name implies, burrowing owls nest and roost in holes in the ground, perhaps dug by prairie dogs, for instance. During a recent ecological survey of fields in rural areas around the cities of Londrina and Uberlandia, burrowing owls and their homes were seen in many over-wintered no-till fields.
A paraquat-based herbicide has become an essential land preparation tool for Brazilian farmers to stem the spread of glyphosate resistant weeds.
The extensive adoption of GM soybean varieties tolerant to glyphosate has led to farmers using this non-selective herbicide for weed control too much and too often. Although glyphosate is encouraging the continued adoption of no-till, with all the benefits to soil conservation that brings, excessive use is also encouraging glyphosate resistant weeds1. Up to three million hectares in Brazil are now estimated to be infested with five weed species which are no longer controlled by glyphosate.
However, an integrated weed control system has been developed to ensure the benefits of glyphosate can be preserved. This involves continuing to spray glyphosate for burndown, but following just before or just after planting the crop with an application of a paraquat-based herbicide. This contains a second active ingredient, diuron. Diuron is a soil residual herbicide, but at the low rates used in this product it has little or no residual effect, but enhances the activity of paraquat.
Soybean growers in Brazil are facing a dilemma. More land under no-till is saving its soil and reducing energy use, but many no-till farmers are now finding that glyphosate resistant weeds are threatening future success.
No-till cropping systems have now been adopted on around 70% of cultivated land in the country, particularly for soybeans. Brazil and the US lead the world in no-till farming, but this is threatened by the rise of glyphosate resistant weeds. A recent article highlighted how worried American farmers are becoming (read more).
This is the first of two features looking at the problem in Brazil – and a success story involving a paraquat-based herbicide.
No-till and GM crops
Paraquat is used to control a huge range of weeds worldwide, but to control weeds effectively and sustainably it is important to understand them.
Why does a plant become a weed? How can different types of weeds be described? What are the features of weeds and the way they grow which can be targeted by herbicides for successful control? Why is paraquat such a useful tool for farmers?
What are weeds?
Weeds are usually described as unwanted plants.  Weeds grow on arable land which is waiting to be planted and then a new flush of weed seedlings emerge with the crop.  In perennial crops like fruit, vines, rubber and oil palm, weeds grow continuously with new growth prompted by the weather and changing seasons.
Weeds are unwanted for many reasons: They compete with crop plants for sunlight, water and soil nutrients, reducing yields and quality.
They may provide a habitat for pests and diseases from which these can attack the crop.
Large, climbing or spiny weeds can make it difficult to get into the crop for pest and disease control, fertilizer application, harvesting and other operations.
Paraquat and sustainable agriculture, by Richard H. Bromilow
In his paper “Paraquat and sustainable agriculture,” author Richard H. Bromilow studies the role paraquat plays in supporting sustainable agriculture around the world.
Abstract: Sustainable agriculture is essential for man's survival, especially given our rapidly increasing population. Expansion of agriculture into remaining areas of natural vegetation is undesirable, as this would reduce biodiversity on the planet. Maintaining or indeed improving crop yields on existing farmed land, whether on a smallholder scale or on larger farms, is thus necessary.
One of the limiting factors is often weed control; biological control of weeds is generally of limited use and mechanical control is either often difficult with machinery or very laborious by hand. Thus the use of herbicides has become very important. Minimum cultivation can also be important, as it reduces the power required to work the soil, limits erosion and helps to maintain the organic matter content of the soil.
This last aspect helps preserve both the structure of soil and its populations of organisms, and also sustains the Earth's soil as a massive sink for carbon, an important consideration in the light of global warming.
Integrated weed management and no-till are advanced agronomic tools with common aims to improve efficiency and profitabilty, while reducing the environmental impact of crop production. Although advanced in concept, these tools are straightforward and can be adapted for use in all cropping systems, from highly mechanised ones to subsistence farming, all around the world.
Tillage is a well proven means of controlling weeds, so are other methods good enough to use in an integrated approach to weed management in no-till systems? This article examines how farmers can reap the rewards of both techniques together.
Farmers around the world know just how hard it is to control weeds. They tend to come back with a vengance, especially when the many elements causing weed problems have not been appreciated and addressed. Aiming to manage weeds rather than control them is not only more realistic, but if Integrated Weed Management (IWM) is applied properly, it can reduce costs, protect the soil, and support pest and disease control.
No-till systems also provide economic and environmental advantages. However, in no-till, the traditional means of weed management by ploughing to prepare a field for cropping is not used. Plowing, even though it effectively removes weeds by burial, is costly, time consuming, and can cause soil erosion and compaction.