# Weed Detection in Rice Fields Using Remote Sensing Technique: A Review
## 3 The Importance of Rice Productivity  
Rice is consumed by around 3.5 billion people worldwide. However, the estimated demand by 2025 is mind-boggling, as rice consumption would grow higher than the population growth in major Asian countries [9]. In general, paddy production had increased globally up to 12% from 1975 to 2008, and nearly 166 million ha of paddy have been harvested in the world [10]. However, in 2020, it was reported that China was the leading country in the world producing paddy (30.5%), followed by India (224.14%), Bangladesh (7.36%), Indonesia (7.14%), Vietnam (5.53%), and Thailand (4.17%) [11]. Numerous research have been conducted to increase the yield of rice production to fulfil consumer demand. [PERSON] et al. [12] had found that the Boterswar variety could help improve the weed-suppressing capacity of rice. The study used five Bangladesh rice varieties named Boterswar, Goria, Biron, Kartiksail, Hashikolmi, and Holoi, and these varieties were planted via a non-weed control method. By using Simpson's diversity index (SDI) to measure the infestation rate of weed species, the relative neighbour effect (RNE), and relative competitive intensity (RCI), results showed that Boterswar facilitated the crop-weed interaction compared to the other varieties. This finding will significantly influence methods to control the presence of weeds in paddy fields. Meanwhile, [PERSON] et al. [13] found that, to increase plant productivity among various crop species, they must improve the photosynthesis rate at the single-leaf level. To achieve this, they used transgenic rice plants that consist of various amounts of the Rieske FeS protein in the cytochrome (cyt) b6/f complex at between 10 and 100% of wild-type levels. As a result, they decreased the electron transport rates through photosystem II, leading to an increased uptake of carbon dioxide (CO\({}^{2}\)) and a successfully increased production yield, up to 40% [14]. Besides improving the photosynthetic activities, improving the irrigation system in paddy is the best practice to increase yield. In Thailand, they practiced an alternate wetting and drying (AWD) method [15]. By setting the threshold at 15 cm of water level below the soil surface for irrigation, this method increased the grain yield by 15% in the wet season and 7% in the dry season, meanwhile improving water usage by 46% and 77% in the wet and dry season, respectively, compared to continuously flooding water into the paddy field. Therefore, the AWD method is a good practice that helps sustain rice production through water-saving. [PERSON] et al. [16] also obtained the same result, and in addition, their study successfully reduced the total arsenic concentration released by rice grain up to 65%. Meanwhile, [PERSON] et al. [17] managed to reduce the methane emissions into the atmosphere by up to 77.1%. Climate conditions played a significant role. The potential rice yield will be affected by severe climate conditions due to increased sterility caused by heat and shortening of the growing season [18]. [PERSON] [19] implemented a geographical information system (GIS) by producing a map of abiotic stresses in Africa using drought, cold, iron toxicity, and salinity or sodicity information as the input. From the analysis, drought was found as the most critical variable that contributes to stress, where 33% of rice area was potentially affected, followed by iron toxicity (12%), and then cold (7%) and salinity/sodicity (2%). [PERSON] et al. [20] used socio-economic, biophysical, farmer population surveys, and secondary remote sensing data on soil characteristics and demand for water to determine drought input parameters in rice-based inland valley production systems. Their study shows that the average annual standardized precipitation evapotranspiration index and groundwater availability duration were the most critical input to determine drought occurrence in their study area. It is crucial to find solutions to improve and increase rice yield.