Organic and inorganic remediation of soils affected by salinity in the Sebkha of Sed El Mesjoune – Marrakech (Morocco)

Abstract

Synchronic and diachronic studies were carried out in order to examine the change of certain soil parameters with time after applying organic (green waste and sugarcane composts) and inorganic (gypsum at two rates) amendments on three soils with different salinity levels using ryegrass as the test crop during a 180-day incubation. The diachronic analysis involved the evaluation of the electrical conductivity dynamics over time. Maximum level of salinization has been observed when applying gypsum (both rates) for the non-saline soil, low gypsum rate (3.8 mg.g−1) for the saline soil, and sugarcane compost for the extremely saline soil. The maximum decrease in salinity was recorded at 120 days for non-saline soil and at 20 days for both saline and extremely saline soils. The synchronic study evaluated at the end of the incubation, showed a relative increase in electrical conductivity (EC) when applying gypsum (all rates) for non-saline soil, after applying green waste compost for the saline soil, and by applying high gypsum rate for extremely saline soil. This analysis also showed an increase in alkalinity and a decrease in organic matter, calcium, and magnesium. However, gypsum application showed, with regard to the other treatments, its effectiveness as a good mineralizer, pH neutralizer, and reservoir of Ca2+ when measured overtime. Maximum potassium uptake by ryegrass at the expense of sodium was obtained at day 60 of incubation, whereas, the highest absorption was not related as expected to the lowest EC whilst, optimum uptake levels were reached in the non-amended soil in the case of non-saline soil, high rate gypsum-amended soil for saline soil and low rate gypsum-amended soil for extremely saline soil.