Paraquat system saves soil in the Philippines

Sloping fields are susceptible to serious soil erosionIn 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. However, using an agronomy system based on paraquat means that weeds are only removed when necessary to protect yields. Even then roots remain intact to anchor the soil. Weeds do not need to be buried by plowing and dead weeds increase soil organic matter which is not then lost by plowing. In the five year Sagip-Lupa project, the production of crops of corn, rice (upland and lowland), potatoes and cabbage is being investigated on five sites using rotations common in each region. Farmers’ traditional methods of hand or mechanical weed control are being compared to using paraquat and 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.

Authoritative On-line References and Resources  A portal for on-line information about no-till farming.
. Typically, a system based on plowing followed by two harrowings, then further operations like hoeing and hand weeding are replaced by a ‘Bilis Saka’ application of paraquat before sowing and later a ‘Bilis Linis’ application sprayed on weeds growing between the crop rows.
Collecting soil eroded from plotsAt each site, plots have been constructed such that soil eroded every time it rains is collected and measured. On the three sites where there is now a full four year’s data, an average of more than 100 tonnes/ha of topsoil has been lost by farming in the traditional way (Fig 1). The large savings of precious topsoil from using paraquat and no-till are all statistically significant. Crop yields have also benefited. The yields shown in Fig 2 are averages of two crops per season over four years. Considering yields of individual crops, over a total of 24 comparisons, the paraquat system significantly out-yielded the traditional system 11 times, performing less well only at one harvest. Paraquat agronomy also gave average savings of between 20% and 67% on input costs, depending on the crop. Accumulated soil losses at three sites over four years for both systemsAverage yields at each site for both systems (Quezon = corn, Batangas = corn/upland rice, Benquet = potato/cabbage)                           Furthermore, measurements of soil organic matter are showing substantial increases when the paraquat system is used. Higher levels of organic matter are generally a strong indication of a healthy soil. Such soils are stable and resist erosion, and also let water infiltrate more quickly. This is important in areas prone to both drought and flooding. The Benguet area has been hit by typhoons and flooding recently, so this very positive news about paraquat is especially timely as the local authorities are working to rehabilitate hard-hit upland farms.