Effect of palm leaf biochar application on some physiological and biochemical characteristics of melon plants (Cucumis melo cv. Samsouri) under drought stress

In order to investigate the effect of palm leaf biochar on some characteristics of Cucumis melo L. under drought stress, a split plot experiment was conducted in a completely randomized block design with three replications for two consecutive years. The main plot was irrigation level (60, 85, and 100% water requirement) and subplot was biochar in four levels (0, 0.18, 0.24, and 0.36 kg/m2). Results showed that treatment of 0.24 kg/m2 biochar and 100% water requirement increased the characteristics of  shoot fresh weight as 77%, shoot dry weight as 32%, root fresh weight as 100%, root dry weight as 84%, root length as 54%, and average fruit weight 84%, water use efficiency as 88%, compared to treatment without biochar and 60% water requirement.  The biocharfree treatment with 60% water requirement accounted for the highest amount of proline due to high stress, and the proline content reduced with increasing biochar and decreasing stress in treatments. The highest level of leaf N, Mn and K, shoot length, leaf area, leaf number, fruit diameter and fruit flesh thickness in the treatment of 0.36 kg/m2 biochar and 100% water requirement were higher 58%, 48%, 65%, 18%, 50%, 95%, 43% and 55%, than to of treatment without biochar and 60% water requirement respectively and had no significant difference with the treatment of 0.24 kg/m2 biochar and 85% water requirement. The highest rates of Fe, Zn and Cu were related to 0.36 kg/m2 biochar and 60% water requirement as 60, 44 and 66% respectively compared to treatment without biochar and 100% water requirement. Generally, the treatments of 0.24 and 0.36 kg/m2 of biochar increased most of the characteristics, however no significant difference was observed between these treatments. Moreover, in 85% water requirement the drought stress conditions could compensate with the application of biochar. Thus, using 0.24 kg/m2 of biochar and 85% of water requirement, recommended for the best result.