Enhancing the quality and yield of Majhoul cultivar dates (Phoenix dactylifera) on a certified organic farm through the application of organic extracts from three seaweed species: Gelidium sesquipedale, Ascophyllum nodosum, and Ecklonia maxima

This study, conducted during the 2022 and 2023 seasons in Tinjdad, Morocco, assessed the effectiveness of three seaweed extracts—Ecklonia maxima, Ascophyllum nodosum, and Gelidium sequipedale—on the yield and quality of Majhoul cultivar dates grown on a certified organic farm. The Ecklonia maxima and Ascophyllum nodosum extracts were obtained from certified organic commercial products, P1® and P2® respectively, while the Gelidium sequipedale extract came from a fermented liquid developed in the laboratory. The experiment included an untreated control group and six treatment groups using extracts at concentrations of 1% and 2% for E. maxima and A. nodosum, applied via foliar spray, and 5% and 10% for G. sequipedale, incorporated into the soil.

Results demonstrated significant effects from all treatments compared to the control group, particularly at higher concentrations. Assessed parameters included yield per palm, date weight, length, and width, as well as content of soluble sugars, reducing and non-reducing sugars, polyphenols, flavonoids, tannins, ash, and antioxidant activity (DPPH and FRAP). In 2023, the application of 2% extracts from seaweed species A. nodosum and E. maxima led to significant improvements over the control group, affecting various parameters: yield per palm increased by 4.97% and 3.72% respectively, date weight by 36.36% and 31.82%, length of dates by 15.70% and 13.95%, dry matter by 23.84% and 19.76%, content of soluble sugars by 6.09% and 5.32%, reducing sugars by 6.49% and 5.63%, ash content by 11.01% and 10.55%, polyphenols by 5.12% and 3.80%, and tannins remained consistent at an increase of 2.48% for both. Additionally, the treatments exhibited significant enhancements in antioxidant activity; the application of 2% Ecklonia maxima led to improvements of 12.20% in DPPH inhibition and 7.53% in FRAP values. Similarly, the 2% Ascophyllum nodosum extract demonstrated significant enhancements, with a 14.32% increase in DPPH inhibition and an 8.70% increase in FRAP values, highlighting the potent antioxidant properties of these seaweed extracts.

The use of 10% fermented G. sequipedale liquid also demonstrated significant improvements in the second year of the study, achieving an increase in yield per palm of 4.06%, date length of 9.59%, date weight of 18.84%, dry matter of 14.7%, soluble sugar content of 5.39%, reducing sugars of 5.60%, polyphenols of 2.33%, and tannins of 1.98% over the control group. Furthermore, this treatment showed significant enhancements in antioxidant activity, with a 10.08% improvement in DPPH inhibition and a 5.75% increase in FRAP values compared to the control.

These findings highlight the significant potential of selected seaweed extracts to enhance the production and quality of Majhoul cultivar dates, particularly positioning the Gelidium sequipedale extract, a marine algae species abundant in Morocco, as a promising alternative for organic and sustainable agricultural practices capable of replacing chemical stimulants in arid oasis regions.