Enhancing lavender productivity in sandy soils using combined applications of poultry manure extract, humic acid, and dry yeast

Lavender is an important aromatic plant valued for its essential oil in pharmaceutical and food applications; however, its cultivation and productivity are frequently restricted by the unfavorable properties of Egypt’s sandy soils. Organic biostimulants offer a sustainable approach to improving lavender productivity under sandy soil conditions. Therefore, this study investigated the effects of poultry manure extract, humic acid and dry yeast, applied individually or in combination, on the productivity of lavender plants grown in sandy soil. Two harvests were conducted at 75 and 195 days after transplanting, and the data were analyzed using two-ways (ANOVA-2). At the second harvest, the combined application of poultry manure extract, humic acid, and dry yeast reached its highest values for all measured traits, including fresh and dry weights (243.3 and 65.4 g plant -1 ), chlorophyll a , chlorophyll b , and carotenoids (1.1, 0.9, and 0.8 mg g -1 , respectively), essential oil content (2.6%), essential oil yield (1.7 g plant -1 ), eucalyptol (276.2 mg plant -1 ), carbohydrate (25.5%), protein (17.8%), phenol (22.2 mg g⁻¹), flavonoid (9.9 mg g -1 ), and free-radical scavenging activity (61.3%) and N uptake; while, the maximum values of NP and k (2.9, 0.8 and 1.1%); P and K uptake values (0.7 and 0.9 g plant -1 , respectively) were recorded with the same treatment at the first harvest. Chemical fertilizers at the first harvest recorded the lowest values for all measured traits, including fresh and dry weights ( 102 and 25 g plant -1 ), chlorophyll a , chlorophyll b , and carotenoids (0,3, 0.2, and 0.3 mg g -1 , respectively), essential oil content (1.1%), essential oil yield (0.3 g plant -1 ), eucalyptol (213.2 mg plant -1 ), carbohydrate (18.5%), protein (14.7%), phenol (14.9 mg g⁻¹), flavonoid (5.8 mg g -1 ), and free-radical scavenging activity (44.3%), as well as N, P, and K contents (1.7%, 0.2%, and 0.3%, respectively), N,P and K uptakes (0.4, 0.1 and 0.1 g g -1 , respectively). The use of organic biostimulants in reclaimed sandy soils effectively enhances lavender productivity and quality, offering a sustainable approach for cultivation in arid regions while increasing its value as a natural source of food and pharmaceutical products.