Biochar (B) application to sandy soils improves its productivity and mitigates climate change. A pot experiment was conducted to investigate the potential effects of maize stalks biochar applied to a zucchini (Cucurbita pepo L. var.Hybrid fadwa) grown on a calcareous sandy soil. Plastic pots were filed with three kilograms of the studied soil and amended by the biochar at levels of 0 (control, unamended soil), 6.3 (B1), 12.6 (B2), and 25.5 (B3) g pot‒1. The pots were planted with zucchini plants and designed in a complete randomized design with three replications. Amending the soil with the biochar significantly increased the soil organic matter, fresh fruit yield, nitrogen use effiency (NUE) and agronomic efficiency of applied nitrogen (AE N) of zucchiniplants. Biochar additions improved the fresh fruits by 26.7, 55, and 195.0 % for B1, B2 and B3 treatments respectively, over the control. The NUE of the plants increased owing to the application of biochar to the soil from 69.2 mg fruit/mg N at the control treatment to 77.1, 84.3 and 131.4 mg fruit/mg N for B1, B2 and B3 treatments, respectively. So, it is recommended to apply biochar as an amendment to the calcareous sandy soil in order to improve its fertility.

A pot experiment was conducted to investigate effects of biochar produced from corn cobs on some chemical properties and potassium status in a calcareous sandy soil. The addition of biochar to this soil resulted in significant increases (P ≤ 0.05) in the soil pH, organic matter (OM), soluble potassium, and available potassium. The soil potential buffering capacity of potassium (PBC^K) significantly increased with adding the biochar to the calcareous sandy soil. Significant increases were also occurred in the activity ratio of potassium at equilibrium ( with the applying the biochar to this soil. Moreover, biochar additions gave significant increases in the labile pool of K value of the calcareous sandy soil. The fresh and dry weight as well as potassium content of wheat plants grown in the calcareous sandy soil significantly increased with biochar additions.