The influence of humic substrates on the efficiency of mineral nutrition elements and cucumber yield in greenhouses

The possibility of achieving high agricultural yields in greenhouse hydroponics has been proven. Further work to improve soilless plant cultivation is associated with certain challenges in increasing yields. These challenges are primarily due to the conflict between the plants' nutrient requirements and the water-air balance of the roots. This often leads to a decrease in yield after three years of growing plants on the same gravel substrate.

One method to overcome these shortcomings is to incorporate organic matter into hydroponic substrates. Various methods have been proposed for introducing organic matter into hydroponics: using iron in the form of its organic salts, adding humic complexes or organic-rich soil to the nutrient solution, and using peat as a substrate. Today, specialized preparations such as Mind Agro.Bio are also being used .

The normalizing effect of humic substances on plant development in unfavorable conditions was the reason for searching for methods of using them in hydroponics.

As fundamental research shows, when growing plants using organic litter, root collars and old roots are exposed to the moist atmosphere of the litter and the space beneath it. Young roots must obtain nutrients from an aqueous nutrient solution; the thickness of the air gap between the solution and the litter can be increased to 15 cm as the root system grows. Organic litter helps stabilize the balance of nutrients entering the plant and supplies the plant with physiologically active humic substances through the root system.

Our specialists conducted experiments to determine the effect of a humified substrate on the yield of Raketa cucumbers grown hydroponically. The experiments were conducted in a modern greenhouse complex in 2024–2025.

The experiments were designed in two variants:

• 1 - growing cucumbers on crushed stone in hydroponic conditions;
• 2 - growing cucumbers in an aqueous nutrient solution using organic bedding and adding Mind Agro.Bio .

The number of plants per square meter is 5. The experiment is repeated 10 times.

In the first variant, cucumbers were grown in a greenhouse complex's industrial hydroponic system. The rack troughs, each containing a pipe with holes punched in it and lined with polyethylene film for added waterproofing, were filled with crushed stone. The crushed stone was basalt and granite, with fractions of 10-25 mm (90%) and 5-10 mm (10%). The aqueous nutrient solution was a standard complex one.

In the second variant, cucumbers were grown on a rack identical to the first, but with the crushed stone removed. The rack contained 2 x 1-meter frames made of 60 x 100 mm wooden beams. A support mesh with 25 x 25 mm mesh size was stretched underneath the frames. A thin layer of straw was placed on top of the mesh to reduce the mesh openings. A layer of organic matter mixed with crushed stone (in equal parts) was placed on top of the straw layer. The crushed stone was the same as in the first variant.

The nutrient solution was poured into the rack trough so that there was a 5 cm air space between its surface and the mesh with bedding.

The cucumber cultivation techniques were identical in both treatments. The substrate was kept moist by watering twice a week.

Seedlings for both treatments were grown hydroponically and planted level, 25–27 cm tall, with six true leaves. Root substrate was added periodically and simultaneously throughout the experiment.

Pinching of stems (1st order - above the second leaf, 2nd order - first whip - above the sixth-seventh leaf and the second whip - above the 4th-5th leaf, 3rd order - above the ovary) was carried out in a timely manner and simultaneously throughout the experiment.

The cucumber harvest was recorded using the continuous recording method at the same time as in the production areas (Table 1).

Table 1. Cucumber yield for one month of the harvesting period, kg/m²

R of experience in % 5.05 | 5.61
HSR 0.95 kg/m² 1.00 | 1.12

The results of the total yield for the variants show that in the two-year repetition, the percentage increase in the variant with organic matter was approximately equal and amounted to about 23% of the control.

In the experiments of both years, the increase in harvest proceeds relatively evenly and in the variant with a humic substrate, over time, it tends to increase in comparison with the control.

On a substrate supplemented with organic matter, cucumber plants, despite identical pinching, grew taller and had more foliage. Their roots covered the entire volume of the aqueous nutrient solution in the tray. On this substrate, the cucumbers' vegetative mass accumulation was 182% greater than that of plants grown on gravel.

The concentration of nutrients in the solution in the variant with an organic substrate was more stable in the experiments of both years.

The percentage of use of mineral nutrition elements by plants in the variant with organic matter was equal to 8.28% in total, compared to 2.85% in the control (Table 2).

Table 2. Use of mineral fertilizers when growing cucumbers

Такая значительная разница в стабильности водных питательных растворов, степени использования элементов питания и в урожае показывает нормализующее влияние веществ гумусовой природы на онтогенез растений, выращиваемых в условиях принудительного питания.

Этот вывод, подчеркиваемый и раньше исследователями, подтверждается и в наших опытах. Попытки введения органических веществ в водную питательную среду при выращивании сельскохозяйственной продукции в условиях гидропоники имеют серьезнейшие основания и изучение этого вопроса должно быть продолжено.

Экспертная ремарка Agro.Bio: Развитие идей использования гуминовых веществ в закрытом грунте сегодня реализуется через высокотехнологичные жидкие комплексы. Применение препаратов, таких как Mind Agro.Bio, позволяет добиться тех же результатов стимуляции корневой системы и стабилизации питания в современных гидропонных системах без необходимости использования громоздких органических подстилок.