Field Crop 2024, Vol.7, No.3, 145-157 http://cropscipublisher.com/index.php/fc 147 3 Environmental Impact Categories 3.1 Water usage and management Water management practices in rice cultivation significantly influence environmental impacts. Non-continuous flooding methods, such as alternate wetting and drying (AWD), have been shown to reduce methane (CH4) emissions by 53% compared to continuous flooding, although they increase nitrous oxide (N2O) emissions by 105% (Jiang et al., 2019). AWD also saves water, reducing water usage by 10% in the dry season and 19% in the wet season (Win et al., 2021). However, intermittent irrigation can increase net greenhouse gas emissions and decrease rice yield (Shang et al., 2021). 3.2 Soil health and fertility Soil health and fertility are critical for sustainable rice production. The incorporation of organic amendments, such as straw and manure, can enhance soil organic carbon stocks and improve soil fertility (Janz et al., 2019). For instance, the eco-rice system (ER) in China improved soil fertility by increasing organic matter, total nitrogen, and available potassium content (Yang et al., 2019). However, the use of organic amendments can also lead to higher greenhouse gas emissions, particularly CH4, during the decomposition process. 3.3 Greenhouse gas emissions Rice cultivation is a significant source of greenhouse gas emissions, primarily CH4 and N2O. Different rice cultivation systems and management practices have varying impacts on these emissions. Ecological rice-cropping systems (ERSs) can reduce CH4 emissions by 12.5% but increase N2O emissions by 11.3% compared to traditional systems (Sun et al., 2021). Diversified cropping systems, such as rice-maize rotations, can lower annual yield-scaled global warming potential (GWP) compared to traditional rice-rice systems (Janz et al., 2019). Additionally, replacing synthetic nitrogen with organic fertilizer can decrease net greenhouse gas emissions and improve rice yield (Shang et al., 2021). 3.4 Biodiversity and ecosystem services Biodiversity and ecosystem services are essential for maintaining the ecological balance in rice cultivation systems. Integrated systems, such as rice-fish (Figure 1), rice-duck and rice-crayfish, have been shown to enhance biodiversity and provide ecosystem services, such as pest control and nutrient cycling (Sun et al., 2021). These systems can also reduce the global warming potential and greenhouse gas intensity. The use of vegetated drainage ditches in eco-rice systems can further improve nutrient removal efficiency and support biodiversity (Yang et al., 2019). Arunrat and Sereenonchai (2022) compare the ecosystem service contributions of rice-fish co-culture and rice monoculture systems. In the rice-fish co-culture system (a), maintaining soil nutrients and climate control are the primary services, accounting for 49.11% and 47.83%, respectively. Pest control constitutes a minor 1.93%. The detailed breakdown shows significant contributions to gas regulation (CO2 fixation) at 0.71% and air purification at 0.07%. In contrast, the rice monoculture system (b) places a greater emphasis on maintaining soil nutrients (51.07%) and climate control (47.16%), but with a notably lower pest control contribution at 0.44%. Gas regulation (CO2 fixation) is higher at 1.03%, and air purification remains consistent at 0.07%. While both systems prioritize soil nutrient maintenance and climate control, the rice-fish co-culture system offers slightly more balanced ecosystem services, including enhanced pest control and water storage benefits. This comparison highlights the potential environmental advantages of integrated agricultural practices. 3.5 Agrochemical use and pollution The use of agrochemicals, particularly nitrogen fertilizers, has significant environmental impacts. High nitrogen rates can lead to increased acidification and terrestrial eutrophication (Tayefeh et al., 2018). Transgenic rice cultivars, which require fewer insecticides, can reduce the environmental and human health impacts associated with chemical inputs (Dastan et al., 2019). Additionally, integrated systems that utilize biogas production from cattle manure can reduce methane emissions and energy consumption, contributing to lower environmental impacts (Ogino et al., 2021).
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