Water Quality in Irrigated Paddy Systems

Abstract

Irrigated paddy rice (Oryza sativa L.) is a staple food for roughly half of the world'spopulation. Concerns over water quality have arisen in recent decades, particularly in China, which is the largest rice-producing country in the world and has the most intensive use of nutrients and water in rice production. On the one hand, the poor water quality has constrained the use of water for irrigation to paddy systems in many areas of the world. On the other hand, nutrient losses from paddy production systems contribute to contamination and eutrophication of freshwater bodies. Here, we review rice production, water requirement, water quality issues, and management options to minimize nutrient losses from paddy systems. We conclude that management of nutrient source, rate, timing, and placement should be combined with the management of irrigation and drainage water to reduce nitrogen and phosphorus losses from paddies. More research is needed to identify cost-effective monitoring approaches and mitigation options, and relevant extension and policy should be enforced to achieve water quality goals. The review is preliminarily based on China's scenario, but it would also provide valuable information for other rice-producing countries.

River Water Quality Monitoring at Paddy Field in Merlimau, Melaka

“…Poor salinity level in irrigation water around these two areas is normally due to the mixing of seawater with fresh water, the excessive usage of fertiliser in the plantation and animal waste from poultry factory. Since, there is nothing much that can be dependent on the water quality from the river, water quality management in paddy fields needs to be taken into consideration to apply "4R" nutrients stewardship proposed by Liu et al (2018) where the source, the rate, the timing and placement of fertiliser must be right.…”

“…Water can easily dilute anything surrounding them, whether it is contaminants or nutrients in the surrounding water environment which will result in water quality in paddy systems (Liu et al, 2018). Salinity is one of the main variables of abiotic stress that can reduce the efficiency of rice production.…”

Water Quality of the Mun River in Thailand—Spatiotemporal Variations and Potential Causes

“…However, the correlation between nitrogen (NO 3 -N and NH 3 -N) and proportions of agricultural land were very significantly negative, with correlation coefficients up to −0.70 and −0.79, respectively. One of the important reasons is that 70% of agricultural land in the basin is paddy field, having intensive uses of nutrient, both nitrogen and phosphorus, and potentially causing eutrophication in the water bodies [57]. The negative trend between rice field proportion and nitrogen could imply lower contributions of the nitrogen into the water bodies as compared to other competing land use type, such as the urban and built-up lands.…”

Residue Monitoring of Propiconazole in the Rice–Crab Co-Culture Field and its Toxicity and Bioaccumulation to Eriocheir sinensis

“…Food shortage has become an urgent problem to be solved because of the rapid growth of population and limited water and soil resources (Bashir et al, 2020;Xu et al, 2021;Zhang et al, 2021). As one of the important staple foods, rice (Oryza sativa L.) feeds roughly half of the global population (Fageria, 2007;Liu et al, 2018). However, rice production systems have been identified as a major sector wasting available water resources, consuming up to 90 percent of irrigation water in Asia.…”