Economics of Weed Management in Maize in Pailin Province Cambodia

Abstract

In Pailin Province, Cambodia, small-holder farm households derive most of their income from upland cash crops such as cassava, maize, soybean, mungbean and sesame. Since the end of the Khmer Rouge civil war in 1998, large areas of rainforest have been cleared opening the way for rapid expansion of cropping, especially maize. The crop expansion has occurred on ferrosols and vertosols which had high initial fertility after clearing. Continuous cropping with maize has resulted in a decline in soil fertility and an increase in losses due to biotic factors, especially weeds which have contributed to a decline in maize yields. Due to the increased cost of agricultural labour, farmers have rapidly taken up the use of herbicides for weed control in maize. A survey of 88 households in 6 villages was carried out to determine the effectiveness and economics of weed control methods for maize, being used by farmers. The results indicate that farmers are moving away from the traditional two cultivations for land preparation and two in-crop hand weedings. This has been due to replacement of the second ploughing with pre- sowing glyphosate, and the replacement of hand-weeding with selective in-crop herbicides in response to the cost and scarcity of labour. Although the current herbicide-based system for maize is working well, it is not likely to be sustainable without crop rotations and use of a wider range of herbicides. Maize crops in Pailin are being invaded by Sorghum weed species, and these species are not controlled by the commonly used atrazine. Rotation of crops and herbicides will be necessary to prevent a build up of naturally resistant weeds and development of genetic herbicide resistance in weed populations.