# Weed Detection in Rice Fields Using Remote Sensing Technique: A Review
## 6 Impact of Weeds Management on Crops, Yield and Economy  
Weeds cause severe yield losses in agriculture [103] and cause significant damage to the ecosystem and the economy in the territories they enter [104]. For example, a couple of studies have reported that rice production's total yield loss due to weed infestation could be up to 72% [105; 106]. This loss happened due to the presence of weeds in crops that compete in nutrient uptake. In addition, uncontrolled chemical products used to control weeds cause farmers health issues and negatively affect the climate, killing livestock and contaminating the air and water [100].  
Fertilizer given by the farmers to increase their yield was not 100% absorbed by their crops. For example, in Cambodia, cultivated agricultural land is 3.7 million hectares, of which 76% is planted with lowland rice and 24% with upland crops such as soybean, cassava, vegetables, maize, and sugar cane. At approximately 3 t ha\({}^{-1}\), their average rice paddy yield was about 50%, and another 50% of losses were caused by weed competition, which is a significant constraint [107]. Due to weeds, Iranian wheat and chicken yield losses are more than 25% and 66%, respectively [108].  
Weeds are more competitive when moisture is inadequate, and rice seedlings cannot cope well with weeds. Meanwhile, in China, the presence of such invasive species has caused them an economic loss of approximately USD 15 billion [109]. In Pakistan, USD 3 billion is needed annually for a weed management program to increase yield [33]. In England, approximately USD 545 million of gross profit were lost annually, equal to 0.8 million tonnes of yield production, due to the herbicide-resistant weeds [110].  
Precision agriculture techniques using high-tech tools can minimize agriculture resources by site-specific application since they can calculate an optimum input to spatial and temporal requirements, reducing greenhouse gas emissions into the atmosphere. Inaddition, these techniques will positively affect economics and yield productivity with a lower production cost than traditional practices [111].  
Malaysian farmers could expect an additional return of rice yield from 0.3 to 0.6 tha-1 through proper weed management [112]. Meanwhile, in India, improved weed management successfully decreased weed infestation in rice fields from very high intensity (>75%) to a mild (50%) level [113]. [PERSON] [114] tested herbicide usage using a spraying UAV to demonstrate the impact of technology adaptation into precision farming. The result showed that the study used approximately 200 L of herbicide per hectare than the traditional method, which is 1000 L per hectare. Meanwhile, by applying site-specific treatment maps on a broad scale, [PERSON] et al. [77] successfully saved herbicide consumption from 58.3% to 70.8%. On the other hand, [PERSON], [PERSON] and [PERSON] [83] saved 61.31% for the no-treatment areas and 13.02% for the low-dose of herbicide practice. The implementation of SSWM into PA proved that it effectively decreased the herbicide cost, optimized weed control, and avoided unnecessary environmental polulations [108; 109; 115; 116].