The Impact of Humic Fertilizers on the Quality of Potatoes, Cabbage, Tomatoes, Beets, and Corn in Various Soil-Climatic Zones of Ukraine

With the correct application of mineral and organic fertilizers, not only the yield of agricultural crops increases but also their quality. However, one-sided nutrition, such as nitrogen fertilizers, can lead to a decrease in starch content in potatoes, sugar in sugar beets, and other quality indicators. Thus, by regulating soil nutrition conditions in different soil-climatic zones, it is possible to manage crop formation both quantitatively and qualitatively.

Humic fertilizers applied in various soil-climatic zones of Ukraine have a positive impact on yield. In this regard, it became necessary to determine how they affect harvest quality depending on the conditions of their application.

Research Methodology

To accomplish this task, samples of various agricultural crops were collected during harvest from three main variants:

1. Control (no fertilizers);
2. Humic fertilizers;
3. Mineral equivalent to humic fertilizer.

Samples were collected according to the initial sampling methodology. The following indicators were determined in the samples:

• Sugar content using the Bertrand method;
• Starch content using the polarimetric method by Ewers;
• Vitamin C using the Murri method;
• Crude protein and total nitrogen using the Kjeldahl method;
• Total acidity of vegetables using the Ermakov method;
• Total phosphorus using the Deniges method modified by Malyugin and Khrenova.

Research Results

The Impact of Humic Fertilizers on Potato Quality

Research on the impact of humic fertilizers on potato quality was conducted in Polissya, Forest-Steppe, and Steppe zones. In Polissya, humic fertilizers were applied broadcast under cultivation and locally in planting holes, while in Forest-Steppe and Steppe zones, they were applied only locally in planting holes. The results of humic fertilizers applied broadcast in Polissya conditions are presented in Tables 1 and 2.

The data in the tables show that the positive impact of humic fertilizers on potato quality depends on varietal characteristics and growing conditions. For example, in the Repkinsky district of Chernihiv Oblast, humic fertilizers tested over three years (Table 1) contributed to an increase in starch, nitrogen, phosphorus content, and, to a lesser extent, vitamin C in potato tubers.

In 2021, the Mind Extra preparation increased starch content by 1.1% compared to the unfertilized control. Mineral fertilizers in equivalent amounts also improved harvest quality, but their effect was less pronounced. The combined application of Mind Extra with mineral fertilizers in 2020 increased starch content by only 0.4%, while the mineral equivalent even reduced starch content in the tubers, likely due to the dry conditions of the year.

The influence of humic and mineral fertilizers on nitrogen and phosphorus content in tubers and their removal by the harvest was more stable. In Kyiv Oblast (Table 2), the effect of humic fertilizers on the chemical composition of potato tubers was similar to the results in Chernihiv Oblast. The increase in starch content for Variety No. 1 with Mind Extra (2 l/ha) was 1.1%, and for Variety No. 2 with double application, it was 2.5%. An increase in vitamin C content was observed only for Variety No. 1.

Mineral fertilizers equivalent to Mind Extra also had a positive effect, but their impact was lower than that of Mind Extra (2 l/ha) combined with the Adept Agro.Bio growth stimulant. From a practical standpoint, the increase in starch and crude protein yield per unit area with the use of humic and mineral fertilizers is important.

Local application of Mind Extra in planting holes for potatoes in Polissya, Forest-Steppe, and Steppe zones also contributed to improved harvest quality and increased nitrogen and phosphorus removal (Table 3). The effect of humic fertilizers in Polissya and Forest-Steppe was significantly higher than in the Steppe, which is explained by the lower content of physiologically active humic acids in sod-podzolic soils compared to chernozems and chestnut soils of the Steppe.

The Impact of Humic Fertilizers on Cabbage Quality

Changes in cabbage harvest quality under the influence of Mind Extra, applied locally, were studied over three years in Polissya and Steppe zones. The analysis results are presented in Table 4.

In Polissya, Mind Extra (2 l/ha) did not cause noticeable changes in vitamin C, sugar, or total acidity content but increased nitrogen and phosphorus content, their removal, and protein yield. In the Steppe, the application of Mind Extra increased sugar content (by 0.4--1.1%) and vitamin C, especially in Varieties No. 4 and No. 5. Changes in total acidity were minor and within measurement error margins. Mineral fertilizers in equivalent amounts were inferior to humic fertilizers in their impact on cabbage quality. Despite the lack of significant increases in nitrogen and phosphorus content in the Steppe, their removal with the harvest increased by 15--46% compared to the control.

The Impact of Humic Fertilizers on Sugar Beet Quality

Chemical analyses of sugar beets were conducted in the Repkinsky district of Chernihiv Oblast over two years. The results are presented in Table 5.

In Polissya, Mind Extra (2 l/ha) increased sugar content by 2%, and with the addition of the Adept Agro.Bio growth stimulant, it increased by 0.6% compared to the control and mineral equivalents. Nitrogen content in the beet harvest increased slightly, but crude protein yield increased by 1.5--2 times due to higher yields. The removal of nitrogen and phosphorus with the harvest of root crops also increased sharply, especially under the influence of humic fertilizers.

The Impact of Humic Fertilizers on Tomato Quality

Tomato quality is characterized by sugar, acid, and vitamin content. It is known that phosphorus and potassium fertilizers improve fruit quality, while excessive nitrogen nutrition reduces carbohydrate, dry matter, and ascorbic acid content. In this regard, the impact of Mind Extra humic fertilizers on tomato fruit quality was studied.

Chemical analyses were conducted over three years in the Nikopol district of Dnipropetrovsk Oblast. Local application of Mind Extra and potassium humate increased sugar content in the fruits compared to the control and mineral equivalent. Vitamin C content did not change, and fruit acidity, converted to malic acid, showed a tendency toward a slight increase.

The Impact of Humic Fertilizers on Corn Quality

Chemical analyses of corn grain were conducted over three years in the Forest-Steppe and Steppe zones. The results are presented in Tables 6 and 7.

In the Forest-Steppe, Mind Extra (2 l/ha), applied broadcast under cultivation, increased starch and crude protein content in the grain, as well as the gross protein output per hectare, compared to the control and mineral equivalent. Humic fertilizers contributed to increased nitrogen and phosphorus content in the grain, which increased their removal by the harvest. The combined application of Mind Extra with mineral fertilizers ensured the highest removal of nitrogen and phosphorus.

In the Steppe, the effect of Mind Extra varied by year. In 2019, starch, nitrogen, and phosphorus content did not increase, but crude protein yield and nitrogen removal increased by 11%, and phosphorus removal by 10%. In 2021, there was an increase in starch, nitrogen, and phosphorus content, leading to a 43% increase in protein yield and a 43% and 66% increase in nitrogen and phosphorus removal, respectively. Superphosphate did not have a positive effect on harvest quality, except for increasing phosphorus content in 2021.

Conclusions

1. Humic fertilizers Mind Extra and Adept Agro.Bio have a positive impact on the quality of agricultural products.
2. The effect of humic fertilizers on the chemical composition of products from various crops and varieties depends on the soil-climatic conditions of Ukraine.
3. In Polissya and Forest-Steppe, the influence of humic fertilizers on improving product quality is more stable than in the Steppe.
4. The question of the impact of humic fertilizers on product quality in different soil-climatic zones requires further study.