Bentonite clay combined with organic amendments to enhance soil fertility in oasis agrosystem

Abstract

Soils in arid and semi-arid lands are vulnerable to climate change, erosion, and mismanagement practices that contribute to organic matter depletion and nutrients imbalances. Oasis agrosystems are considered one of the major farming systems in some parts of these lands in the Middle East and North Africa region. However, oases soils are inherently low in organic carbon due to their sandy texture which retains little water and binds low organic matter contents, and the accelerated decomposition rates of organic matter under high temperature, which makes its accumulation difficult. Traditional farming practices in oasis agrosystems have always integrated organic matter derived from livestock to enhance organic carbon (OC) and total nitrogen (TN) stocks in the soil. This study is aimed to examine the potential effects of a new mixture of organic amendments and bentonite clay on organic carbon and total nitrogen stock accumulation in the soil. Five amendments were applied including sand and compost (SC), sand and manure (SM), sand, bentonite, and compost (SBC), sand, bentonite, and manure (SBM), and sand mixed with bentonite (SB). These treatments were compared to untreated soil (U). The results showed that OC and TN stocks increased significantly (p<0.05) in all three depths of the five treatments compared to the untreated soil. Higher organic carbon stocks (2862±3.4 g m−2) were detected in SBM treatment. The combined organic and mineral amendment retarded OC and TN decomposition. After two years of the amendments’ application, 30% of OC remained in the soil for SBC treatment. In conclusion, the mixed mineral and organic amendment is a better choice to preserve OC and, thus, maintain oasis soil fertility.