In the Philippines, more successful results from a project using paraquat to control weeds and prevent soil erosion have been announced.
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. 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.
At 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.
Furthermore, measurements of soil organic matter are showing substantial increases when the paraquat system is used. 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.