Soil erosion

Tea is a thriving crop in Vietnam and farmers rely on paraquat for a weed control system that reduces soil erosion.  Much of the tea crop is grown on sloping land prone to losing very significant amounts of soil each year.
Results of research conducted by the Northern Mountainous Agriculture and Forestry Science Institute show that using paraquat for weed control instead of hand hoeing can save huge amounts of soil. Paraquat is more effective than glyphosate because it leaves roots intact to anchor the soil.
Tea in Vietnam
Tea is an important industry in Vietnam with six million people involved in production, processing and exporting1. Tea is a native plant to the country and has been cultivated for thousands of years. The industry has been experiencing a rapid expansion since the mid 1990s. Yields have also improved, more than doubling over this period, and now approach the best in Asia2. Exports of tea are increasing and efforts are being made to improve the international image of Vietnamese tea. Vietnamese black tea is generally used in blends. However, fine quality green teas are produced and drunk by the Vietnamese people.
Lower costs and favorable environmental effects when using paraquat: these were the key conclusions from a four-year comparison of weed control methods in bananas, recently completed by the University of the Philippines.
The trial was conducted on a commercial plantation on Mindanao, the large southern island of the country. Bananas make a significant contribution to the economy of the Philippines being a major fruit export. New plantations are being established on more sloping land where soil erosion poses a real threat to sustainable production. Filipino authorities estimate that 623 million tonnes of soil are lost annually from 28 million hectares of land.
Erosion can be reduced by maintaining a vegetative cover on the soil. So, it is important to manage weeds so that they give as much cover as possible to help avoid erosion, but not to allow them to compete with the crop. Two weed control programs were compared. In the field trial, traditional methods of hand weeding and slashing with a machete called a bolo were compared to a monthly spray program in a sequence of two applications of paraquat followed by one of glyphosate. In the latter two years of the trial, these regimes were modified to match changing patterns of weed growth, and weeds were controlled only by paraquat when a threshold of 30% ground cover was breached.
Farmers in the mountains of Vietnam can plant maize crops more than two weeks early by using paraquat in a conservation tillage system. Timely operations are essential in growing all crops and paraquat’s unprecedented speed of action is often a huge help to farmers up against the weather or looking for earlier harvests to get the best prices.
Results of research conducted by The Northern Mountainous Agriculture and Forestry Science Institute (NOMAFSI) show that using paraquat for weed control increased maize yields by more than 50%1. Early planting was crucial to good yields – land preparation with slow acting glyphosate herbicide resulted in much lower yields.
In the Philippines, more successful results from a project using paraquat to control weeds and prevent soil erosion have been announced. Since 2005, researchers from several universities and other organisations have been collaborating to study approaches to reducing the serious threat posed by soil erosion to food production and the environment.
Professor Gil Magsino from the University of the Philippines presented the results and conclusions from the Sagip-Lupa project’s 4th Annual Report at the University of Benguet recently.
Prof. Magsino noted that an annual loss of 2 – 4 cm of topsoil from fields in the Philippines has become commonplace, but with the imperative of achieving sufficient levels of food production this cannot be sustained.
Benefits of paraquat-based agronomy Less soil lost
Higher yields
Lower input costs
Time savings
Plants and soil organic matter are key to reducing soil erosion. Living or dead mulches of plants covering the soil resist the impact of rain, and roots and organic matter bind soil particles together. Traditional methods of weed control such as hand hoeing and plowing remove unwanted plant material, ie weeds, and disturb the soil, encouraging erosion.
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.
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.
Will farming and soil quality collide?
World Agriculture and the Environment is an important new book addressing the fear that increasing demand for food and fiber is on a “collision course” with soil quality.
This article is in two parts. In Part One, some of the main issues discussed in the book are reviewed. Part Two then explains how more than 50 years of research and practical use have shown that controlling weeds with paraquat can help provide improved and sustainable crop management practices to improve soil quality.
Part One: What ‘World Agriculture and the Environment’ says
In World Agriculture and the Environment authorJason Clay (World Wildlife Fund-US vice president, Center for Conservation Innovation) reviews the production and environmental impact of 21 of the world’s major food commodities. The main threats to the environment posed by crops, fish and meat are identified and explored, as well as the trends that shape those threats.
Major Issues
Extensive long-term field studies confirm - and governments and regulatory authorities, worldwide, agree - that normal use of paraquat in accordance with the approved label instructions does not cause an unacceptable environmental impact.
These studies have shown that:
Paraquat is inactive in soil
When paraquat residues come into contact with the soil the paraquat active ingredient rapidly becomes adsorbed and strongly bound to clay and organic matter in the soil. It becomes biologically inert and as a result it cannot be taken up by plant roots or other organisms. Paraquat treated soils still maintain an active soil ecosystem with no adverse effects on soil microbes, microorganisms and earthworms. Paraquat cannot be released from the soil or re-activated by the application of water or other agrochemicals.
All agricultural soils, not only those with high clay content, have a high capacity to absorb paraquat.
Mr. Prasanna Srinivasan of New Dehli, India, is a recognized expert in the field of economics, policy and regulatory development and specializes in the impact of global environmental treaties on developing countries. Syngenta commissioned Mr. Srinivasan to provide a balanced assessment of the benefits and risks of pesticides in general and paraquat in particular. Mr. Srinivasan recently completed this review entitled, “Paraquat: A unique contributor to agriculture and sustainable development.
Please click on this link to download a copy of the review:
Paraquat: A Unique Contributor to Agriculture and Sustainable Development