Mechanised spraying systems for herbicide application

The control of competing vegetation is an important operation in the establishment of crops, and appropriate herbicide application can be a cost-effective weeding solution. Although the use of herbicides is now well established in agriculture practice, manual methods of application still predominate. Herbicides are one of the most important tools for managing weeds in direct-seeded rice systems. Herbicide use in these systems is expected to increase in the near future because of the non availability of labor at the critical time of weeding and high labor cost. Herbicide use is also very important where there is a morphological similarity between weeds and rice, especially in a broadcast crop. Depending on the country, various pre and post emergence herbicides are recommended and used in direct-seeded systems. Some of the pre-emergence herbicides for dry-seeded rice systems are oxadiazon, oxadiargyl, and pendimethalin. As rice seeds are broadcast on the soil surface in wet-seeded rice, pretilachlor (with safener) is usually recommended as a pre-emergence application. Various kinds of spray nozzles are used including a flat fan, even fan; flood nozzle, variable cone, and hollow cone. Flat fan nozzles are used in multiple-nozzle booms as the spray pattern is tapered from the centre to the edges. To achieve effective weed control, the use of pre-emergence herbicides is a must in direct-seeded systems, especially in dry-seeded ones.