Agricultural residues are generated during the production and processing of agricultural crops. Under modern date palm plantation practices, field operations generate huge quantities of residues, which are discarded with little valorization. The date palm agro-industry produces significant amounts of waste. The accumulation of these residues can cause ecological damage to the oasis ecosystems. There is a lack of comprehensive data on long-term research studies that aim to assess the impact of date palm waste management practices. Composting and/or pyrolysis of date palm residues showed benefits for improving soil physical and chemical properties, particularly in sandy soils. This claim holds particular significance for arid and semi-arid regions, which are characterized by low fertility and are susceptible to soil degradation, accentuated by ongoing climate change. This review summarizes the existing literature concerning the valorization of date palm residues with regards to compost and pyrolysis processes, as well as the impact of their application on soil quality. Further research is required to assess the effects of using date palm residues for better soil amendment management. Research should focus on composting and biochar technologies for date palm residues and their application in arid and semi-arid regions to combat soil erosion and degradation. Increasing the beneficial uses of date palm residues could lead to sustainable and economic growth in dry areas.

Generally, soils of arid and semi-arid regions have low water retention properties due to high sand and low organic carbon contents. This study aimed at quantifying the effect of date palm-based organic amendments (OAs) on the water retention properties of two soils (sandy loam and silty loam), as well as the influence of sand supplementation (0.5–2 mm) on the magnitude of the effect of OAs. Different grain size distributions were obtained by adding sand to natural soils. For this purpose, sand was added to the two soils (1/3 and 2/3) and different soil-OA combinations were tested at a dose of 3% by mass: compost alone, biochar alone and a mixture of biochar and compost (50:50 in mass), in addition to unamended control soils. Soil water contents were measured at nine matric potentials ranging from the saturation to the permanent wilting point. Biochar was more efficient than compost at improving soil water retention. The effect of organic amendments on water retention increased with sand content. In most cases, soil water content values were significantly higher for biochar-amended soils than for unamended or compost-amended soils. The weakness of the effect of compost addition (if alone) was probably due to its properties and notably its high mineral content and electrical conductivity. Soil sand supplementation led to higher differences between the OA-amended soils and unamended soils. Changes in available water capacity reached +26% and +80% in a sandy loamy soil enriched with 2/3 sand and amended with compost and with biochar, respectively, compared to the unamended soil. These results show that sand content (and more generally, soil texture) influences the effect of OA application. Thus, the application of biochar from date palm residues in soil seems to be an effective solution to improve the water retention properties of coarse textured soils and contribute to optimizing the use of water resources in irrigated areas.

Background: Soil salinity poses a significant threat to agricultural lands by adversely affecting soil properties, crop productivity, and, consequently, global food security. This study evaluated the effects of date palm waste compost (C), applied alone or combined with biochar (BCC) or Ramial chipped wood (RCWC), on soil properties and barley yield under arid and saline conditions. Methods: A field experiment was performed in a completely random design with three replications. In addition to the unamended soil (control), treatments with compost (C), biochar + compost (BCC) and Ramial chipped wood + compost (RCWC) were tested. We monitored soil physico-chemical parameters, straw biomass, grain yield, and soluble sugar levels over two crop seasons. Results: All treatments enhanced soil fertility. However, the sodium adsorption ratio (SAR) and the cation ratio of soil structural stability (CROSS) increased in soils amended with compost alone in the second crop year. Barley (Hordeum vulgare L.) cultivated in soil amended with C and BCC produced 28% and 37% more dry biomass, respectively, in the second year, while no significant effects were observed in the first year. This may be attributed to the higher availability of nutrient content (N and P) in soils during the second year. In the first year, plants amended with BCC exhibited the highest accumulation of sucrose and fructose, with increases of up to 39% and 66%, respectively. Conclusions: Compost application did not affect barley yield during the first crop year, highlighting limited effects on soil fertility. However, C and BCC improved barley yield in the second year after application. No synergistic effect was observed between biochar, Ramial chipped wood, and compost. Future Perspective: Further studies should focus on the long-term effects of organic soil management, including salinity issues, to support sustainable agriculture in arid regions.

Besides their potential for carbon sequestration, compost and biochar application in agriculture may constitute an alternative to mineral fertilizers by improving soil fertility and productivity in carbon- poor soils. This study focused on the im pact of biochar and compost produced from date palm residues on nitrogen (N) leaching and plant uptake in a sandy soil cultivated with barley under arid cli matic conditions. In addition to the unamended control soil (S), treatments with biochar (BC), urea (U), biochar + urea (BCU), compost (C) and biochar + com post (BCC) were tested. We followed soil fertility parameters, N leaching losses, N uptake and plant growth. Results showed a significant increase of barley yields with compost compared to urea (+66%) treatment (U), biochar amended (BC) and unamended soil (S). Biochar alone or co- applied with a nutrient source seems to reduce barley shoot biomass and grain yields at short term. Leachate N recov ery and soil extractable inorganic N at the end of barley cultivation indicated that compost did not provide N in excess at barley maturation stage. Compost amended soils led to the highest N losses through leaching and thus environ mental risk of N vertical transfer. However, compost had positive effects on soil nutrient status and barley yields. No synergistic effect was observed between bio char and compost. In conclusion, this paper highlights that date palm compost improved barley productivity in a coarse- textured soil, but with very short- term effects concerning available soil N.

The cultivated dryland soils of North Africa present low fertility and productivity due to low organic matter content (Brahim et al., 2021). Date palm residues are an abundant resource in these regions and only a minor part is recovered in oasian agroecosystems. The ISFERALDA project – Improving Soil FERtility in Arid and semi-arid lands using Local organic DAte palm residues – aims at developing the use of organic amendments based on traditional production (composting and slow pyrolysis) as a key tool to improve soil fertility and soil properties.The objective of this study was to quantify the effects of compost and biochar based on date palm residues on soil water retention. Two soils with properties similar to North Africa soils (sandy loam texture, alkaline pH, low organic matter content) were collected in a semi-arid Mediterranean area of southeast Spain. In addition, and in order to test further the influence of soil texture, soil sand content was artificially increased by supplementing the natural soils with washed quartz sand. The different types of organic amendments were tested at a dose of 60 t/ha (Edeh et al., 2020): compost alone, biochar alone and mixture of compost and biochar (50:50 in weight). Water content was measured using pressure membrane apparatus at nine different matric potential (pF), ranging from the saturation to the permanent wilting point.The results showed that water retention was higher in soil with organic amendments regardless of the pF and the soil type. For a specific soil, the addition of biochar alone or in combination with compost to the soil resulted in higher values than compost alone. The improvement in water retention properties was more pronounced for soils amended with sand. Thus, composting and/or pyrolysis of date palm residues is a viable alternative to improve the water retention properties of sandy and loamy soils. Keywords:Date palm – arid and semi-arid lands – organic amendments – soil water retentionReferences :Brahim, N., Karbout, N., Latifa, D., & Bouajila, A. (2021). Global Landscape of Organic Carbon and Total Nitrogen in the Soils of Oasis Ecosystems in Southern Tunisia. Agronomy, 11, 1‑17.Edeh, I. G., Mašek, O., & Buss, W. (2020). A meta-analysis on biochar’s effects on soil water properties—New insights and future research challenges. The Science of the Total Environment, 714, 136857. https://doi.org/10.1016/j.scitotenv.2020.136857