The effect of magnesium aminochelate and seaweed (Sargassum angustifolium) on improving growth and quality characteristics of cucumber in magnesium-deficient nutrient solution

Background and Objectives: Magnesium is an essential element for plant growth. Additionally, magnesium plays an important role in carbohydrate partitioning and dry matter production between the root and shoot. One of the main challenges facing vegetable producers in greenhouses in southern Iran is magnesium deficiency, especially in the middle of the growing season, due to various reasons such as poor water quality and excessive use and irrational consumption of potassium fertilizers in the reproductive phase. Therefore, finding practical solutions that help reduce the use of chemical fertilizers, production costs, environmental risks, increase efficiency, performance, and improve food security and sustainable agriculture is essential. The present study aims to propose a practical solution for improving the growth and quality of greenhouse cucumbers under conditions of reduced magnesium in the nutrient solution, while reducing fertilizer consumption, by using magnesium amino chelates and native seaweed extracts from the Persian Gulf.

Materials and Methods: This experiment was conducted in the autumn and winter of 2022-2023 in the educational-research greenhouse in Shahid Chamran University of Ahvaz, in a split-plot design as a basic block with complete randomization and three replicates. The experimental treatments included foliar application of different concentrations of magnesium aminochelate (0, 2.5, and 5 ml/L) and seaweed extract of Sargassum angustifolium (0, 1.5, and 3 g/L). The foliar application of magnesium aminochelate and seaweed extract started two weeks after transplanting and continued once a week until one week before harvest (a total of 8 weeks out of 11 weeks). During the growing season and after the treatment effects, growth and quantitative factors such as root, stem, and leaf fresh and dry weight, leaf number and area, fruit fresh weight, fruit length and diameter, and qualitative factors such as TSS, pH, and EC of fruit juice, titratable acidity, fruit firmness, and fruit dry matter percentage were measured in cucumber plants.

Results: The results of the interaction between different concentrations of magnesium aminochelate and seaweed extract showed that with increasing magnesium concentration up to 5 ml/L and seaweed extract up to 3 g/L, there was a significant increase in root, stem, and leaf fresh and dry weight, leaf number and area, and fruit fresh weight. The Mg3×S3 treatment (5 ml/L of magnesium aminochelate and 3 g per liter of seaweed extract) and the control treatment (Mg1×S1) (zero ml/L of magnesium aminochlate and zero g/L of algal extract) had the highest and lowest values of growth indices, respectively. Increasing the levels of seaweed extract up to the 3 g/L and concentration of magnesium aminochlate up to the level of 5 ml/L led to a twofold increase in fruit fresh weight. The highest TSS of fruit juice was observed in the Mg3×S3 treatment (4.73%) and the lowest in the control treatment (Mg1×S1) (2.13%). The results of this study showed that in the reduced magnesium solution, simultaneous increase in seaweed extract and magnesium aminochelate led to an increase in cucumber fruit dry matter percentage. The lowest fruit dry matter percentage was observed in the Mg1×S1 treatment (2.27%), while the highest was observed in the Mg3×S3 treatment (4.78%).

Conclusion: The findings of this experiment showed that the use of magnesium aminochelate probably increases chlorophyll production and seaweed extract through biomass improvement and growth stimulation ameliorates the growth, yield, and quality characteristics of cucumber fruit. Based on the results of this study, the use of 5 ml/L of magnesium aminochelate and 3 g/L of seaweed extract is recommended to improve the growth, yield, and quality indices of greenhouse cucumber under magnesium deficiency conditions.