Integrative effect of activated biochar to reduce water stress impact and enhance antioxidant capacity in crops.

Biochar is a soil amendment that can change soil's physical and hydraulic properties. However, biochar application is far from being a 'one size fits-all' approach. The impact of the management practices is dependent on biochar type (feedstock and production conditions), application depth and method, climate and site characteristics. Hence, this study aims to enrich the available inconclusive information on how biochar could affect clay loamy soil and to assess the potential impact of the induced change on water stress mitigation of rain-fed durum wheat under the specific condition of the semi-arid environment of North West of Tunisia. A field experiment was investigated in which three biochar rates 0 (B0), 10 (equivalent to 0.5% of weight) (B1) and 20 t/ha (equivalent to 1% of weight), (B2), were tested. Other laboratory analysis allowed the evaluation of soil water retention curve (SWRC), saturated hydraulic conductivity (Ks), dry density (ρb) and biostress biomarkers such as glutathione-S-transferase (GST), catalase activities (CAT) and malondialdehyde content (MDA) as well as yield attributes. Results showed that treatment B2 significantly decreased ρb and Ks with relative change values of about -3.1% and -19%. Consequently, SWRC showed a better water retention capacity, mostly from saturation to matric potential value (h) of 33 kPa. Total (TAWC), plant (PAWC) and readily (RAWC) available water contents, significantly increased under B2 with relative changes of +6%, +44% and +44% respectively. Moreover, GST and CAT were also boosted under B2. Consequently, biological and grain yields as well as grain water use efficiency (GWUE) significantly increased. GWUE increased from 0.81 ± 0.04 in B0 to 1.09 ± 0.01 kg/m3 in B2. The correlation analysis showed a significant and positive correlation, between GWUE and soil water parameters (θs, θfc and θmre) suggesting the indirect effect of biochar on water-use efficiency for grain yield of wheat. Therefore, among the tested rates 20 t/ha could be suggested to improve plant soil water availability and reduce the harmful impact of drought stress on rain-fed durum wheat.

Correction to: Modeling interactions between saturated and un-saturated zones by Hydrus-1D in semi-arid regions (plain of Kairouan, Central Tunisia).

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Modeling interactions between saturated and un-saturated zones by Hydrus-1D in semi-arid regions (plain of Kairouan, Central Tunisia).

In semi-arid areas like the Kairouan region, salinization has become an increasing concern because of the constant irrigation with saline water and over use of groundwater resources, soils, and aquifers. In this study, a methodology has been developed to evaluate groundwater contamination risk based on the unsaturated zone hydraulic properties. Two soil profiles with different ranges of salinity, one located in the north of the plain and another one in the south of plain (each 30 m deep) and both characterized by direct recharge of the aquifer, were chosen. Simulations were conducted with Hydrus-1D code using measured precipitation data for the period 1998-2003 and calculated evapotranspiration for both chosen profiles. Four combinations of initial conditions of water content and salt concentration were used for the simulation process in order to find the best match between simulated and measured values. The success of the calibration of Hydrus-1D allowed the investigation of some scenarios in order to assess the contamination risk under different natural conditions. The aquifer risk contamination is related to the natural conditions where it increased while facing climate change and temperature increase and decreased in the presence of a clay layer. Hydrus-1D was a useful tool to predict the groundwater level and quality in the case of a direct recharge and in the absence of any information related to the soil layers except for the texture.