Macronutrient distribution in soil subjected to raw sanitary sewage application by closed-end furrows

This work aimed to evsaluate the influence of raw sanitary sewage (RS) application in closed-end and level-bottom furrows on the distribution of macronutrients and sodium in the soil along its depth. The applied amount of RS was controlled due to the harmful effect of sodium, with a weekly application over three consecutive years. The experimental design consisted of two experimental plots receiving RS, one with alternating the site of effluent application (alternation of inlet and outlet—TFA) and the other without alternating the site of application (only inlet—TFN); and two experimental plots receiving conventional mineral fertilization, both irrigated with public water supply, where one alternated the site of water application (alternation of inlet and outlet—TWA) and the other without alternating the site of application (only inlet—TWN). The inversion of the flow direction with RS application in the closed-end furrows (TFA) provided a better distribution of nutrients in the soil along its length. There was no significant difference in the levels of macronutrients and sodium between the initial and final regions of the furrow soil. In contrast, the fixed flow direction experimental unit (TFN) exhibit a significant difference between the initial and final levels of total nitrogen, phosphorus, potassium and sodium in the closed furrows with mean concentrations of 265.2, 16.2, 46.7 and 110.0 mg dm(−3), respectively.