Agricultural and environmental applications of biochar (BC) to soils have received increasing attention as a possible means of improving productivity and sustainability. Most previous studies have focused on tropical soils and more recently temperate soils. However, benefits of BC addition to desert soils where many productivity constraints exist, especially water limitations, have not been widely explored. Thus, three experiments were designed using a desert soil from Saudi Arabia to address three objectives: (1) to evaluate the effect of BCs produced from date palm residues added at 8 t ha⁻¹ on wheat growth, (2) to determine the effect of BC addition and BC aging in soil on water retention, and (3) to reveal the effect of BC on selected soil physical (bulk density, BD; total porosity; TP) and chemical (pH; electrical conductivity, EC; organic matter, OM; cation exchange capacity, CEC) properties. The feedstock (FS) of date palm residues were pyrolyzed at 300, 400, 500, and 600 °C, referred to here as BC300, BC400, BC500, and BC600, respectively. The BC products produced at low temperatures were the most effective in promoting wheat growth when applied with the NPK fertilizer and in enhancing soil water retention, particularly with aging in soil, whereas high -temperature BCs better improved the selected soil physical properties. The low-temperature BCs increased the yield approximately by 19% and improved water retention by 46% when averaged across the incubation period. Higher water retention observed with low-temperature BCs can be related to an increased amount of oxygen-containing functional groups in the low-temperature BCs, rendering BC surfaces less hydrophobic. Only the BC300 treatment showed a consistent positive impact on pH, OM, and CEC. Pyrolysis temperature of date palm residue along with aging are key factors in determining the potential benefit of BC derived from date palm residues added to sandy desert soil.

Textile dyes are organic compounds that can pose an environmental threat if not properly treated. They can cause many problems ranging from human health, ecosystem disturbances, and the reduction of the esthetic value of water bodies. The adsorption process using activated carbon (AC) has been proven to be effective in treating dyes in wastewater. However, the production of AC is limited by the non-renewables and relatively expensive precursor of coal. Date palm residues (DPRs) provide a good alternative for AC’s precursor due to their continuous supply, availability in a large amount, and having good physiochemical properties such as high oxygen element and fixed carbon. This study provides a review of the potential of date palm residues (DPRs) as AC in adsorbing textile dyes and the recent technological advances adopted by researchers in producing DPR-based AC. This review article focuses solely on DPR and not on other biomass waste. This study presents a background review on date palms, textile dyes, biochar, and AC, followed by production methods of AC. In the literature, DPR was carbonized between 250 and 400°C. The conventional heating process employed an activation temperature of 576.85–900°C for physical activation and a maximum of 800°C for physicochemical activation. Chemical agents used in the chemical activation of DPR included NaOH, KOH, ZnCl₂, H₃PO₄, and CaCl₂. The maximum surface area obtained for DPR-AC was 1,092.34 and 950 m²/g for physical and chemical activation, respectively. On the other hand, conditions used in microwave heating were between 540 and 700 W, which resulted in a surface area of 1,123 m²/g. Hydrothermal carbonization (HTC) utilized carbonization temperatures between 150 and 250°C with pressure between 1 and 5 MPa, thus resulting in a surface area between 125.50 and 139.50 m²/g. Isotherm and kinetic models employed in the literature are also discussed, together with the explanation of parameters accompanied by these models. The conversion of DPR into AC was noticed to be more efficient with the advancement of activation methods over the years.

Information on how soil texture and related soil properties affect corn (Zea mays L.) nitrogen (N) response is needed to improve N management in corn production. We conducted a study at 12-site yr in Quebec to assess the effect of N rate (0–250 kg N ha⁻¹) and soil surface textural groups [clay, loam, sandy belonging to the gleysolic soil order (Sg), and sandy belonging to the podzolic soil order (Sp)] on corn grain yield, stover yield, total N uptake (TNU), nitrogen uptake efficiency (NUE), thousand kernel weight (TKW), test weight, and chlorophyll meter readings (CMR). Corn was more responsive to N rate in the clay soil textural group for most of the parameters due to lower soil N supply, and least responsive in the Sp group, except for test weight and CMR, due to possibly greater leaching in this group. The CMR at flowering accounted for 87%, 87%, 82%, and 25% of the variation in grain yield, TNU, TKW, and test weight, respectively. This study suggests that soil surface texture has a major influence on corn N response, but other soil properties such as drainage may also be important.

Industrial activities are associated with various heavy metals (HMs) being emitted into the environment, which may pose a threat to humans and animals. The rapid increase in an industrial activity in major cities in Saudi Arabia (SA) has raised concerns regarding the accumulation of HMs in the environment. The aim of this study is to assess the accumulation of HMs in soil and native plants in an industrial environment. We collected 36 surface soil samples and 12 plant species from 12 sites in an industrial city in central SA. The results showed that the HMs content in the soil followed a descending order of (Fe > Ni > Zn > Pb > Cu> Cr > Cd). The enrichment factor (EF) of HMs in the soil ranged from 0.20 to 7336. Up to 100%, 16.6%, and 6.2% of soil samples were extremely highly enriched with Cd, Ni, and Pb, respectively. Plant species Cyperus laevigatus accumulate Cd, Pb, and Ni. Citrullus colocynthis accumulate Cd and Pb in significantly (p < 0.001) higher amounts than other studied species. The Pollution Load Index (PLI) values for the 12 sites ranged from 0.52–1.33 with S5 and S2 PLI >1.0 indicating progressive deterioration of these sites. The Bioaccumulation Factor (BF) ranged from 0.04–2.76 and revealed that some plant species may be candidates for phytoextraction potential. The most promising plant species for phytoextraction and remediation were annuals or perennials such as Malva parviflora, Sisymbrium irio and Citrullus colocynthis, especially for Cr and Cu. This study suggests that these native plant species may be useful for phytoremediation in the area.

Biochar’s agricultural and environmental benefits have been widely demonstrated; however, it may cause environmental contamination if it contains large amounts of pollutants such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs). Therefore, this study aimed to assess the contents of PAHs and HM in a range of biochars generated from different sources and pyrolysis temperatures. A range of feedstock was converted to biochar, including sewage sludge (SS), olive mill pomace (OP), feather meal (FM), soft offal meal (CSM), chicken manure (CM), and date palm residues (DPR). Each feedstock was then pyrolyzed at three temperatures of 300, 500, or 700 °C, thereby producing a total of 18 types of biochar. These biochar products were analyzed for 16 PAHs and eight metals (Cr, Mn, Fe, Ni, Cu, Zn, Cd, and Pb). Benzo[b]fluoranthene, benzo[k]fluoranthene, and benzo(a)pyrene were significantly greater in the biochar produced at 700 °C than in that produced at 300 °C, especially for CM. The concentrations of dibenz(a,h)anthracene were significantly lower at 700 °C but greater at 500 °C and 300 °C in DPR. Increasing the pyrolysis temperature from 300 to 700 °C significantly increased the concentrations of metals, including Cr in SS and OP; Mn in CM; and Fe, Ni, Cu, and Zn in SS. However, the concentration of Cd was significantly lower in the SS when biochar was produced at 700 °C than at 500 or 300 °C. The type of feedstock used and the pyrolysis temperature are key factors influencing the contents of PAHs and HMs in biochar, both of which need to be considered during the production and use of biochar. Further investigations are recommended to establish the relationships between pyrolysis temperature and types of feedstock and the formation of PAH or the concentrations of metals. Monitoring the concentrations of PAHs and HMs before applying biochar to soil is also recommended.