engleski

Floating hydroponics as a sustainable agricultural practice in nettle cultivation - successful management of nutrient solution

The need for sustainable production of nutrient- rich foods is critical both for environmental protection, mainly to reduce footprint on the soil, water and air, and for human health. Therefore, agricultural practices are increasingly shifting to greenhouse cultivation, where abiotic factors can be controlled and optimized regarding to the specific needs of each plant species. Hydroponic cultivation stands out as a successful growing system that provides a controlled environment, water and nutrient consumption ensuring higher yields, better morphological characteristics and favorable mineral composition. Floating hydroponics is offered as one of the techniques whose main advantages are the elimination of potential problems caused by soil contamination, the possibility of lower water consumption and precise and balanced plant nutrition. Stinging nettle (Urtica dioica L.) is a perennial plant species characterized by the possibility of retrovegetation and multiple harvesting, which makes it interesting for agricultural production. However, it also tends to accumulate heavy metals and excessive amounts of nitrogen from the soil. Therefore, it poses a challenge in terms of questionable plant material for further use and consumption. As nettle becomes more popular among consumers, mainly due to its favorable nutrient composition, high antioxidant and essential minerals content, its cultivation is necessary to ensure consistent chemical composition and high quality. The aim of this study was to determine the effects of nutrient solution (NS) content during two harvesting periods on the morphological characteristics, dry matter and macroelements content of fresh nettle leaves. The experiment was conducted in a heated greenhouse during the fall-winter growing season of 2021/2022. Nettle was grown in basins filled with NS standardized according to Johnson's (EC 1.5 mS/cm). Management of the solution during cultivation was varied as follows: basin 1 (B1) and 2 (B2) were filled with Johnson's solution prepared independently of the water chemical composition while in basin 3 (B3) Johnson's NS was adjusted according to the water chemical analysis. After the first harvest, only water was added in B1 to replace the drop level of NS ; in B2 the initial NS was added ; in B3 the amount of nutrients was added to match the composition of the initial standard solution based on the NS analysis performed after the first harvest. Two harvests were carried out (Nov 3, 2021 and Jan 11, 2022), after each, morphological and chemical analyses were conducted and the results were statistically analyzed. The results show that both factors, NS variation and harvest period, have a significant influence on the morphological characteristics, yield and macroelement content of fresh nettle. In the first harvest, values for nettle plant height (28.53 cm), leaf length (7.57 cm), width (6.07 cm) and yield (1.26 kg/m2), as well as for N and P (5.83% N dry weight (dw) and 1.15% P dw) were generally higher regardless of the solution variant. The second harvest resulted in higher dry matter (22.12%) and K (4.16% K dw) values. The lower values of all morphological parameters and macroelements found in nettle in the basin supplemented with water prove that in case of multiple harvests, correction of NS is necessary to obtain adequate yield and nutritional value of the final product.

Urtica dioica L., dry matter content, macroelements, balanced fertilization, yield

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