The Effectiveness of Safe NPK Alternatives on the Growth, Productivity, and Essential Oil Content of Fennel Plants under Semi-Arid Saline Soils

RECOGNIZING the importance of fennel as a medicinal plant under challenging soil conditions, it becomes essential to prioritize sustainable cultivation methods. Embracing bio-stimulants as a viable alternative to mineral fertilizers can play a pivotal role in ensuring the continued growth and utilization of fennel for its medicinal properties while safeguarding the environment and fostering long-term agricultural viability. The selected alternatives to NPK-fertilizers were included the foliar application of active yeast (5 g L-1), compost tea (2 ml L-1), humic acids (2 ml L-1), seaweed extract (0.5 g L-1), and ascorbic acid (0.5 g L-1), comparing with the negative control (tap water) and positive control as NPK (19:19:19) at 1.5 g L-1. The sequence order of the studied treatments from more effective to less effective was as follows: applied active yeast recorded increase in many studied parameters such as number of branches per plants, dry weight, seed yield per fed, crude protein and total carbohydrates in seeds by 88 and 156%; 137 and 133%; 115 and 129%; 111 and 46%; 16.2 and 11.3% in both seasons, respectively comparing with the negative control and other applied treatments. The main components in fennel oil were a-pinene, followed by sabinene, then ss-pinene under such saline conditions. The results of this study can support the farmers to reduce the applied NPK-mineral fertilizers with supplying the cultivated fennel under such saline soil conditions. Further studies are needed and more evaluations are required to know the best biostimulants can be applied under such salinity stress.