Industrial saline wastewater in a corn-soybean rotation to enhance crop yield without compromising soil health in a subtropical soil

The production of industrial waste has increased in the last decades along with world population. Wastes are used in agriculture as fertilizers and soil amendments depending on their composition, dynamics in soil and effects on plant growth. The aim of this study was to assess the effect of industrial saline wastewater from heparin production on soil chemistry and plant yield in a subtropical soil in Brazil. Five rates of industrial saline wastewater (0, 10, 20, 40 and 60 m3 ha−1 year−1) were applied as fertilizer in a corn -soybean rotation on an Oxisol with limited nutrient availability. Five soils sampling were done: before and after the first application of the industrial wastewater (2017, corn), before and after the second application of wastewater (2018, soybean) and two years after the first application (2019). Soil K, Ca, Mg, Na content and CEC increased immediately after the application of wastewater but they returned to former values with time due to plant uptake and lixiviation. Wastewater application significantly increased corn (all rates) and soybean (only with the highest rate) yields around 103–250% and 50%, respectively, in comparison with no wastewater application. However, the highest rate temporally increased soil Na content and electrical conductivity (up to 650 and 800%, respectively). Although nutrient uptake, chlorophyll content and corn and soybean yields were enhanced, the use of high rates of industrial saline wastewater could cause soil salinization (mainly in locations with low rainfall), affecting soil chemistry and physical parameters due to clay dispersion, and pollution or water bodies.