Effects of different concentrations of municipal wastewater on seed germination and seedling performance of three rice (Oryza sativa L.) varieties

Agriculture is the largest user of fresh water for irrigation. As the demand of fresh water is increasing, there is a need to recycle municipal wastewater for agricultural activities. The objective of the study was to determine the effect of different concentrations (0, 2.5, 5, 10, 25, 50, and 100%) of untreated and treated municipal wastewater on seed germination and seedling performance of fresh and aged rice seeds, seedling nutrient uptake and seedling chlorophyll content. Laboratory experiments were conducted using three Malaysian rice varieties, MR219, MR220 and MR253. This study revealed varying responses of rice for germination percentage, germination rate index, seedling length, seedling fresh weight, seedling dry weight, root volume, root surface area, seedling vigour index, root:shoot ratio and percentage phytotoxicity when the seeds were irrigated with different concentrations of municipal wastewaters. The seeds imbibed in untreated wastewater gave higher values of seed germination and seedling growth and development than treated wastewater. Lower municipal wastewater concentrations (2.5-25%) showed promoting effect on rice seed germination while higher wastewater concentrations (50-100%) retarded seed germination and crop growth and development. Significant difference (p50% inhibit nutrients uptake while lower concentration of municipal wastewater 50% concentration of both untreated and treated municipal wastewater while promoting effects were observed at lower <25% concentration. Positive and significant correlation was indicated between parameters of rice seed germination; seedlings performance and chlorophyll content while all the nutrients elements were negatively and highly correlated with quantity of municipal wastewater. Therefore, municipal wastewater can be used to raise quality seedlings without affecting seedling growth. The results indicated that untreated wastewater is better for rice seed germination and seedling performance than treated wastewater. This can be due to the high amount of nutrient in the untreated municipal wastewater which triggers the physiological process of the seeds that leads to increase in seedling growth and development. This study indicates that municipal wastewater of < 25% concentration is safe enough to be used in irrigation for rice production