Effects on macronutrient contents in soil-plant irrigated with different quality waters and wastewaters
Journal of Water Reuse and Desalination
The goals of this research were focused on investigating the effects of irrigation with untreated wastewater, ozone-enhanced primary treated wastewaters (O 3 EPTW), tap water and tap water þ fertilizer on the macronutrient content in soil and plant tissues. The effect on plant development was evaluated by growing Lactuca sativa in soils irrigated with these different quality waters and wastewaters, and by determining the macronutrients content in water, soil and plants. In this study, the soils
... is study, the soils irrigated with O 3 EPTW showed increased organic matter concentrations, which is advantageous for crop cultivation. The electric conductivity for the O 3 EPTW irrigated soils remained below those of the tap water þ fertilizer and untreated wastewater. The soil irrigated with tap water þ fertilizer showed a marked decrease in pH, and its long-term use could lead to soil acidification. Macronutrient levels in plant tissues (N, K and Mg contents) were similar for all irrigation waters, except for tap water which always remained lower than the others. It was concluded that the use of O 3 EPTW may become a good irrigation alternative that can be employed without the health risks associated with the use of untreated wastewaters, also reducing the adverse effects on soil's salinity or acidification. Conversely, a study in Brazil (Herpin et al. ) found that the use of a secondary effluent to irrigate coffee crops had three major disadvantages: (1) an increase in soil sodicity; (2) a reduction of the soil's organic matter level with a decrease in cationic exchange capacity; and (3) a discrepancy in the nutrient balance for the soil-plant system. That research also found that the soil's N, P and S concentrations were insufficient for coffee cultivation. It was concluded that the macroelements (N, P, K, Mg and Na) content in coffee plant tissues were within the normal ranges for the plant (with the exception of Ca, for which higher values were measured). On the other hand, Kiziloglu et al. () established that the macronutrients content in plant tissue depends on the type and quality of water used for irrigation; the P, K, Ca, Mg and Na content in two crops (cauliflower and squash) decreased in the following order: untreated wastewater > pre-treatment > primary treatment > tap water. Up to this date, there are few investigations regarding macronutrients content in soil-plant systems irrigated with primary treated wastewater (Kiziloglu et al. ), and none with ozonated primary treatment. Most of the published research in this field focuses only on irrigation with biological treatment effluents (Isea et al. ; Heidarpour et al. ; Kalavrouziotis et al. ; García-Delgado et al. ), but not on the effects that can be observed on macronutrient changes by using physical-chemical treatments such as an APT. A previous study (Campos-Reales-Pineda et al. ) demonstrated that the use of an APT that combined the application of ozone at the coagulation step (ozoneenhanced primary treatment, O 3 EAPT), reduced the wastewater's phytotoxicity and improved germination rates during a preliminary evaluation of the influence of the treated effluents on plant seedlings. It was mentioned that those findings could result in beneficial effects such as improved productivities for irrigated plants. Nevertheless, the relationship between the nutrient content of the water, soil and plants was not investigated. Therefore, the aim of the present research is to evaluate the effect of the irrigation with different quality waters and wastewaters (including those subjected to an ozone-enhanced primary treatment) on the macronutrients content in soil and plant tissues of Italian lettuce.