Assessment of growth and yield components of rice irrigated with reclaimed wastewater

• Based on the characteristics of crop growth and crop components, there were no adverse effects of irrigation with reclaimed wastewater.
• This study was conducted without major heavy metal accumulation in soil and crops during five cropping years.
• Reclaimed wastewater irrigation did not impact the rice agro-ecosystem adversely.

The objective of this study is to assess the growth and yield components of rice irrigated with reclaimed domestic wastewater. The experimental plots consisted of four blocks of each of the three irrigation water treatments: groundwater, untreated wastewater, and reclaimed wastewater. Randomized complete block design was applied to the experimental plots (5 m × 5 m). Soil and water quality were monitored during a five cropping period. Crop height and tiller number data were analyzed from 2005 to 2009 according to growth stage. Analysis of variance (ANOVA) and honestly significant difference (HSD) post-hoc tests were applied to compare the rice components and yields from the treatments with the control plot. The wastewater and reclaimed wastewater irrigation plots were significantly higher than groundwater in clum length, panicle number, and rice yield. The total nutrients supplied with irrigation water were highly correlated with rice yield data, suggesting that the higher rice yield from reclaimed wastewater resulted from nutrient supply. The heavy metal contents in the milled rice that was cultivated with the reclaimed wastewater did not show significant differences from rice irrigated with groundwater. Reclaimed wastewater irrigation plots were significantly higher than groundwater irrigation plots in the contents of protein and milled head rice ratio, which had levels similar to or in the middle of conventional rice and brand rice. This study shows that reclaimed wastewater irrigation did not have adverse environmental impacts on the agricultural ecosystem, although long-term monitoring is needed to fully understand its relationships.