Date-Palm Residue Biochar Effects on Rocket (Eruca sativa Mill.) Growth and Soil Chemical Properties

Abstract

Biochar derived from date-palm residues could be considered a valuable resource for agricultural applications. However, its effect depends on application rates and growing conditions. The present study aimed to evaluate the effects of date-palm residue biochar incorporated into soil at 1%, 2%, and 3% (w/w), compared to an untreated control, on rocket (Eruca sativa Mill.) growth and changes in the chemical properties of the growing media. The experiment was laid out in a randomized complete block design (RCBD), comprising 32 planting bags distributed across three blocks, with eight bags per treatment and two plants initially established per bag. Each bag constituted one experimental unit. Plant height increments were analyzed using analysis of variance (ANOVA) in SPSS, and treatment means were compared using Duncan’s multiple range test at the 5% significance level. Soil chemical measurements were summarized descriptively. Soil pH and electrical conductivity (EC) were measured before planting and at the end of the experiment using one representative sample per treatment at each sampling time. These measurements were summarized descriptively. All plants were irrigated with water having an EC of 2.90 mS cm⁻¹, and no fertilizer was applied. Plant height increase was significantly higher in the control (1.81 cm) than in the 1%, 2%, and 3% biochar treatments (0.83, 0.59, and 0.85 cm, respectively) during the first measurement period (p < 0.001), with no significant differences among biochar rates according to Duncan’s multiple range test. Treatment effects were not significant during the second or third intervals (p = 0.472 and 0.919, respectively). Mean cumulative height increments were 2.49, 1.46, 1.06, and 1.48 cm for the control, 1%, 2%, and 3% treatments, respectively. Soil pH declined from 8.70, 8.04, 8.03, and 7.98 before planting to 7.30, 7.50, 7.50, and 7.41 at the end of the experiment for the control, 1%, 2%, and 3% treatments, respectively. Corresponding EC values increased from 0.70, 6.04, 10.02, and 15.95 to 10.60, 13.31, 18.31, and 22.40 mS cm⁻¹. In conclusion, the date-palm biochar application reduced rocket height increment during the first measurement interval, whereas no significant differences were observed among treatments during the second and third intervals.