Influence of organic amendments from date palm residues : impacts on soil water retention and carbon mineralisation in arid and semi-arid regions soils

Elie Le Guyader (1) , Xavier Morvan (1) , Maxime Gommeaux (1) , Vincent Miconnet (1) , Béatrice Marin (1) , Mohamed Moussa (2) , Nissaf Karbout (2) , Ines Rahma Zoghlami (2) , Houda Oueriemmi (2) , Diego Intrigliolo (3) , María José Delgado (4)

1 GEGENAA - Groupe d'Étude sur les Géomatériaux et Environnements Naturels, Anthropiques et Archéologiques - EA 3795
2 Eremology and Combating Desertification Lab. (LR16IRA01), Institute of Arid Regions, Medenine, Medenine 4100, Tunisia
3 Desertification Research Center (CIDE) (CSIC-UV-GVA), 46113 Moncada, Spain
4 Department of Agricultural Chemistry, Geology and Edaphology, University of Murcia, Campus Espinardo, 30100 Murcia, Spain

The cultivated dryland soils of North Africa present low fertility and productivity, mainly due to low organic matter content. Date palm residues are an abundant resource in these regions and only a minor part of residues is valued in oasian agroecosystems. The European project ISFERALDA aims at developing the use of organic amendments produced from date palm residues by traditional processes (composting and slow pyrolysis) as a key tool to improve soil fertility and properties. Experiments were conducted in the laboratory to evaluate the effects of compost and/or biochar amendments on soil water retention properties. A soil with properties close to Saharan oases soils was collected in a semi-arid area of southeast Spain. In addition, soil sand content was artificially increased by supplementing the natural soil (sandy loam texture) with washed quartz sand in order to further test the influence of soil texture. The different types of organic amendments (compost and/or biochar) were tested at a dose of 60 t/ha: compost alone, biochar alone and mixture of compost and biochar (50:50 in weight). Water retention curves were obtained using pressure membrane apparatus at nine different matric potentials (pF), ranging from the saturation to the permanent wilting point. The results showed that water retention was generally improved in soil with organic amendments regardless the pF and the soil type. The higher the sand content was, the more significantly the available water capacity increased with organic amendments. The increase ranged between 4 and 25% in the natural soil and the sand-enriched soil (loamy sand texture), respectively. The soil respiration and nitrogen mineralisation dynamics were measured in a soil incubation experiment. A cultivated sandy soil from a Tunisian oasis was amended with compost (60 t/ha) and/or biochar at different doses (18 and 36 t/ha). All combinations of organic amendments increased soil carbon mineralisation compared to non-amended soil. The highest mineralisation rates were observed in soil amended with compost and biochar, followed by compost alone. CO2 emission were lower if compost + biochar were subjected to a two-week activation period before application to the soil. Those two experiments showed that organic amendments can improve oasian soil properties (water retention and mineralisation of organic matter) and are a relevant way to value local agricultural residues.

Mots clés: Date palm; arid and semi-arid lands; organic amendments; soil water retention; Mineralisation

Domaines: Sciences de l'environnement

Elie Le Guyader, Xavier Morvan, Maxime Gommeaux, Vincent Miconnet, Béatrice Marin, et al.. Influence of organic amendments from date palm residues : impacts on soil water retention and carbon mineralisation in arid and semi-arid regions soils. Transdisciplinary research for a healthy planet, Symposium, Mar 2023, Reims (51), France. ⟨hal-04440962⟩