Impact of the Cultivation System and Pre-Sprouting of Selected Potato Cultivars on the Physico-Chemical Properties and Enzymatic Activity of Soil in the Conditions of Central-Eastern Poland

Abstract

The aim of the study was to demonstrate the effect of the cultivation system, cultivars and pre-sprouting of potato on soil quality. Materials for the research were obtained from a three-year (2016–2018) field experiment in Central-Eastern Poland. The experiment was established using the randomized sub-blocks method, in a dependent system which was as follows: split-split-plot in three replications. The first order factor was the type of cultivation system of organic (E), and sustainable (S). The second order factor was the selection of the six potato cultivars (‘Denar’, ‘Gwiazda’, ‘Jurek’, ‘Satina’, ‘Tajfun’, ‘Jelly’) and the third order factor was the pre-planting treatments of (A) sprouted seed potatoes, and (B) non-sprouted seed potatoes. The organic cultivation system, in comparison to the sustainable system, contributed to changes in the chemical properties of the soil by increasing the content of organic C and total N, thereby narrowing the C:N ratio, reducing the content of mineral N forms, changing soil acidity, and changing in the enzymatic activity of Adh, AFs, and APs in the soil. Germination of seed-potatoes contributed to the increase in total N and nitrate N in the soil, to extend the C:N ratio. The sustainable development of agriculture in the soil and climate conditions of Central-Eastern Poland can be achieved by maintaining soil fertility and improving its productivity, and reducing the risk of the agricultural system by increasing the flexibility of integrated agriculture.

1. Introduction

Soil is considered living because of its abundance of billions of microorganisms, the ability to maintain our food system, regulate and filter fresh water, and store massive amounts of carbon. It is a key component of human survival, but with increasing global problems, soil is now becoming a major problem in combination with climate change. Soil health may be a viable solution to this global problem. A healthy soil is capable of achieving all the sustainable goals that have been adopted by the United Nations General Assembly [1]. Soil health is defined by Doran et al. [2] as “the ability of living soil to function within natural or managed ecosystems, to maintain plant and animal productivity, maintain or improve water and air quality, and promote plant and animal health”. Due to anthropogenic activity or natural interference, the condition of the soil deteriorates drastically. Soil is the largest sink for carbon storage and plays a key role in nutrient cycling and maintaining soil health. Microorganisms, especially effective microorganisms, can help with this. All transformations of biogenic elements taking place in the soil are stimulated by enzymes that determine their transformation into forms available to plants [3]. Therefore, cultivated soil has a high level of biological activity, which, among other factors, is determined by soil microorganisms and enzymes secreted by them. The level of activity is an indicator of soil fertility and provides information on organic changes in the soil environment [1,2,3,4,5]. According to Bielińska et al. [3], and Natywa and Sawicka [4], the biological activity of enzymes is dependent on the pH of the soil, water and air relations, and organic matter content, which are shaped by crop production systems, simplification of tillage, fertilization, as well as the species and cultivar of the crop. Barabasz and Vořišek [6], as well as Natywa and Sawicka [4], claim that agronomic factors, such as crop rotation, vernalization, fertilization and other agrotechnical treatments have a significant impact on soil microbial activity. According to Flis-Bujak et al. [7], improper agricultural practices and improper fertilization can lead to disturbances in the functioning of agro-ecosystems and contribute to the formation of various compounds in the soil environment, such as ammonia, mycotoxins, or nitrosamines, which in turn can have a negative impact on the development of part of the soil microflora, but also on the level of crops, including potatoes.

The importance of potatoes in Poland, despite the downward trend, results from the possibility of the versatile use of tubers of this species. It is the basic ingredient of everyday food, with high nutritional values and a low energy value at the same time. Its annual consumption per capita in Poland is decreasing and currently amounts to approx. 92 kg/person/year, but will still be approx. 50% higher than in the vast majority of European Union countries [8,9]. The demand for edible potato varieties is related to the growing demands of consumers as to the quality of tubers. Potatoes intended for direct consumption or food processing must meet certain quality requirements to ensure food safety [9]. Such safety can be ensured by growing potatoes in the organic system. According to Zarzyńska and Goliszewski [10], potato production in this system is difficult, but promising and profitable. Organic potato finds buyers against the background of mass domestic production. There will be more of them in the future, when society is richer, if it trusts that a product labeled “organic” is indeed an organic product. However, this requires farmers to change their outlook, undergo the certification procedure and, above all, to learn about organic potato production. In organic farming, potato varieties are sought not only based on good quality features, but also on whether they have a high resistance to diseases and pests, especially resistance to Phytopthora infestans and the most important viral diseases (PVY, PLRV) [11,12,13]. The use of genetically resistant varieties to late blight is very important, especially in organic farming, because chemical plant protection should not be used there. Hence, the conducted research aimed at determining the impact of the application of a sustainable and ecological system on the level of soil culture. Additionally, potato is usually grown on light and well-ventilated soils, susceptible to degradation processes such as acidification, a decline in humus, blockage of mineral nutrients, reduced biological activity, leaching, and loss of biodiversity. The use of enzyme assays for the evaluation of factors inhibiting these processes is important not only because of yield and its quality, but also from environmentally friendly point of view. Determining soil biological activity and understanding the factors that regulate enzyme activity is essential for characterizing metabolic potential, fertility and soil quality [4,5,14,15]. Therefore, the aim of this study was to compare some of the physicochemical properties and the biological enzymatic activity of soil under potato cultivation in organic and sustainable management system.

The research assumed the following three research hypotheses:

• The first alternative hypothesis is that the use of an organic farming system will optimize the biological balance in the soil by changing the activity of selected soil enzymes (Adh, AF, AU and AP) compared to the null hypothesis that the organic farming system will not cause significant changes in their activity;
• The second research alternative hypothesis assumes that the use of a balanced cultivation system against the background of constant nitrogen-phosphorus-potassium fertilization and the use of compost will change N forms in the soil, and optimize the biological balance in soil, against the null hypothesis that the use of a balanced system will not change the balance of N forms in the soil;
• The third alternative hypothesis is that the use of sprouted potatoes for planting, in an ecological and sustainable cultivation system, will optimize the biological balance in the soil by changing the activity of soil enzymes (Adh, AF, AU and AP) and improve the C: N ratio in the soil, compared to the null hypothesis that the cultivation systems do not have a significant effect on changes in enzyme activity and will not affect the soil C: N ratio.

2. Materials and Methods

The experiment was conducted in 2016–2018 at the Experimental Station in Parczew (51°38′ N, 22°54′ E), on Luvisol [16].

Parczew is located in the functional area of Polesie. According to the physical and geographic division, the Parczew area is part of the Western Polesie macroregion belonging to the Polesie sub-province, which is part of the Eastern Baltic-Belarusian Lowland province (Figure 1a,b). The soils in Parczew were formed on sandy-clay formations of water-glacial origin, including mainly tills, sand and gravel, and organogenic formations with extensive accumulation in valleys. The dominant role is played by the white-headed soils found on the plateau. These are acidified soils. They were created in a cool and humid climate under coniferous vegetation. They were made from rocks poor in alkaline components, especially from sandy deposits of various origin. Luvisols are classified as medium quality soils. The granulometric composition of loamy sand, developing into clay of a good rye-complex, is slightly acidic [16].

2.1. Experimental Design

The experiment was established using the randomized sub-blocks method in a dependent system of split-split-plot in three replications. The first order factors were cultivation systems of organic (E), and sustainable (S). The second order factors were potato cultivars (‘Denar’—very early, ‘Gwiazda’—early, ‘Jurek’, ‘Satina’ and ‘Tajfun’—medium early; ‘Jelly’—medium late/late) and the third order factor was the pre-planting treatments of (A) sprouted seed potatoes, (B) non-sprouted seed potatoes. The area of each plot was 19.6 m² for harvest. The seeding material of the tested cultivars was of E grade (EU).

Agrotechnical and Plant Protection Treatments

Seed potato was planted at a spacing of 70 × 35 cm in the third decade of April. In objects with sprouting, the seed potatoes were vernalized for four weeks in optimal conditions (light daylight or artificial fluorescent lamps suspended between rows for 10–12 h daily, temperature of 12–15 °C and relative air humidity of about 80–85%, preventing the tubers from drying out). Different rotations and production technologies were applied in each of the systems that were used (

Table 1. Selected elements of potato cultivation in different crop production systems.

Specification	Crop Production System *
	Sustainable	Organic
Fertilization	biennial compost (straw + red clover + hay)—36 t ha−1 + NPK—114-62-62 kg ha−1.	Biennial compost (straw + red clover + hay)—36 t ha−1; post-crop biomass with mineral potassium fertilizers with addition of magnesium and sulphur containing KS—75-25 kg along with patent kali (KMgS–75-15-27 kg ha−1).
Weed control	mechanical + herbicides	Mechanical + manual weeding (40–55 h ha−1).
	Linurex 500 SC (linuron) —1.8 dm−3 ha−1, (one treatment)
	Targa Super 050 EC (chizalofop-P-etylowy) —1.5 dm−3 ha−1 (one treatment).
Potato beetle control	Actara 25 WG (tiametoksam) —80 g ha−1 (two treatements)	(Novodor 02 SC (Bacillus thuringiensis subspecies tenebrionis ATCC-1252, strain NB 176—20 g in 1 kg of agent, 10,000 BTTU g−1)—2.5 dm−3 ha−1 (two measures). SpinTor 240 SC (Spinosad) (0.05–0.1 dm−3 ha−1) (one measure).
	Karate Zeon 050 SC (lambda cyhalotryna) —0.12 dm−3 ha−1 (one treatment)
	Proteus 110 OD (tiachlopryd + deltametryna)—0.4 dm−3 ha−1 (one treatment)
Potato blight and Alternariosis protection	Tanos 50 WG (cymoksanil + famoksat)—0.7 kg ha−1 (one treatements)	Funguran-OH 50 WP (copper in the form of cupric hydroxide—76.8% [767.7 g/kg]) 2.0 kg·ha−1 (two treatments). Miedzian Extra 350 SC (copper oxychloride)—350 g Cu–3 dm−3 ha−1 (one treatment).
	Infinito 867.5 SC (propamocarb hydrochloride + fluopicolide) 1.6 dm3 ha−1 (one treatment)
	Curzate 49.5 WP (cymoksanil + copper)—3.0 kg ha−1 (1 treatment)
	Ekonom 72 WG (mancozeb + metalaxyl)—2.0 kg ha−1 (one treatment)
Defoliation	Reglone 200 SL (diquat—200 g dm−3) (‘Jurek’, ‘Tajfun’—3 dm−3 ha−1; ‘Denar’, ‘Gwiazda’, ‘Satina’, ‘Jelly’—2 dm−3 ha−1)	-

* potato ⇒ spring barley ⇒ red clover ⇒ winter wheat ⇒ stubble crop (white mustard + spring vetch); Source: own research.

).

In the sustainable system (S) (potato ⇒ spring barley ⇒ red clover ⇒ winter triticale + post-crop (perk + white mustard [5 + 15 kg ha⁻¹]), phosphorus-potassium fertilization balanced the uptake at an amount of 114 kg N, 62 kg P, 62 kg K, 2-year-old compost (straw + red clover + hay) was applied at a dose of 36 t ha⁻¹, and intercrop biomass was used only once per rotation for potato. Mechanical tending treatments were applied following the emergence of potatoes and consisted of rolling and single dredging combined with harrowing. Just before emergence, the herbicide which destroys dicotyledonous weeds (Linurex 500 SC—1.8 dm⁻³ ha⁻¹) was applied, and Targa Super 050 EC (1.5 dm⁻³ ha⁻¹) was applied with 2–3 leaves of monocotyledons. Chemical plant protection treatments were made using the pest hazard thresholds. Potato blight was composted using Tanos 50 WG—0.7 kg ha⁻¹; Infinito 867.5 SC—1.6 dm³ ha⁻¹, Curzate 49.5 WP—3.0 kg ha⁻¹, and Ekonom 72 WG—2.0 kg ha⁻¹. Against potato beetle, two treatments of Actara 25 WG—80 g ha⁻¹, Karate Zeon 050 SC—0.12 dm⁻³ ha⁻¹; Proteus 110 OD—0.4 dm⁻³ ha⁻¹ were applied. Defoliation was performed with the Reglone 200 SL preparation tool in doses depending on the cultivars’ early age (Table 1). Chemical plant protection treatments were used with the thresholds of the harmfulness of pests. The tubers were harvested 10 days after desiccation (Table 1). Plant protection products were diluted with 300–400 dm⁻³ of water ha⁻¹.

In the organic cultivation system (E), the following rotations were used: potato ⇒ spring barley ⇒ red clover with grasses ⇒ winter wheat + post-crop (faba beans + peas [200 + 100 kg ha⁻¹]). Organic fertilization, i.e., 2-year-old compost (straw + red clover + hay) at the amount of 36 t·ha⁻¹ and post-crop biomass with mineral potassium fertilizers with the addition of magnesium and sulfur containing KS—75–25 kg along with patent kali containing Kegs’ -75-15-27 kg in a pure component due to large deficiencies of potassium and magnesium in the soil, was used in the organic system. In total, 150-15-52 kg ha⁻¹ of KMgS was introduced into the soil. The weed infestation was controlled by applying indirect (proper rotation, proper selection of cultivars, early planting dates, fertilization in accordance with organic farming requirements) and direct methods (mechanical and manual weed control). Referring to pesticides, only bacterial preparations permissible in organic farming (Bacillus thuringiensis ssp. tenebrionis) against potato beetle, as well as copper fungicides against Alternaria solani and Phytophthora infestans, such as Funguran-OH 50 WP—2.0 kg ha⁻¹ (2 treatments) and Miedzian Extra 350 SC—3 dm⁻³·ha⁻¹ (1 treatment), were applied after being diluted with 300–400 dm⁻¹ of water ha⁻¹. Novodor 02 SC—2.5 dm⁻³ ha⁻¹ and SpinTor 240 SC (0.1 dm⁻³ ha⁻¹), were used against potato beetle (Table 1).

2.2. Characteristic of Potato Cultivars

The qualitative and resistance characteristics of the cultivars evaluated are presented in

Table 2. A description of potato cultivars.

Trait of Cultivar	‘Denar’	‘Gwiazda’	‘Jurek’	‘Satina’	‘Tajfun’	‘Jelly’
Maturity time	very early	early	medium early	medium early	Medium early	medium late/late
Flesh color	light yellow	light yellow	yellow	yellow	yellow	yellow
Skin color	yellow	yellow	yellow	yellow	yellow	yellow
Tuber shape	round-oval	round-oval	round-oval	round-oval	oval	oblong-oval
Cooking type *	AB	B	B-BC	B	B-BC	B
Resistance to late blight on a 9° scale	3°	3°	5°	3°	5°	5°
Resistance to PVY on a 9° scale	7°	7°	8°	5°	7°	5°
Resistance to PLRV on a 9° scale	7°	7°	6°	7°	7°	5°

* Culinary type A—salad, not overcooking. Their flesh remains firm after cooking and can be easily cut; Cooking type B: Potatoes slightly floury, disintegrating and with rather fine-textured flesh (European Association for Potato Research cooking type scale); Cooking type C: Potatoes dry, with flour.

.

2.3. Meteorological Conditions

Air temperature and rainfall distributions during the experiment varied (

Table 3. Rainfall, air temperature and the hydrothermal of coefficient of Sielianinov, during the growing season of potato, according to the meteorological station in Uhnin (2016–2018).

Year	Month	Rainfall [mm]				Air temperature [°C]				Hydrothermal Coefficient of Sielianinov *
		Decade of Month			Sum in Month	Decade of Month			Mean
		1	2	3		1	2	3
2016	IV	1.6	20.7	20.7	43.0	9.3	9.5	14.3	11.1	1.3
	V	20.3	62.0	59.1	141.4	11.0	13.2	19.2	14.7	3.1
	VI	32.5	3.7	49.0	85.2	16.4	15.9	15.2	15.9	1.8
	VII	4.0	54.2	11.5	69.7	19.9	20.7	22.5	21.1	1.1
	VIII	21.7	44.1	30.0	95.8	23.2	19.2	15.6	19.2	1.6
	IX	1.9	5.0	12.7	19.6	16.3	15.6	12.0	14.6	0.5
	Total				454.7
2017	IV	14.6	5.9	41.3	61.8	5.4	8.6	12.4	8.8	2.3
	V	23.4	13.9	83.0	120.3	12.6	12.0	13.7	12.8	3.0
	VI	5.4	16.5	24.8	46.7	17.7	16.3	16.1	16.7	0.9
	VII	10.5	21.6	13.1	45.2	19.6	18.7	19.9	19.4	0.8
	VIII	0.4	0.0	5.7	6.1	23.4	20.6	20.3	21.4	0.1
	IX	32.4	32.6	65.2	130.2	16.0	17.7	12.8	15.5	2.8
	Total				1319.7
2018	IV	11.5	22.2	13.4	47.1	10.9	10.1	9.0	10.0	1.6
	V	4.9	2.8	38.6	46.3	14.4	17.8	12.9	15.3	1.0
	VI	10.1	43.2	34.0	87.3	16.6	17.5	23.0	19.1	1.5
	VII	22.4	30.8	60.9	114.1	19.5	20.1	21.9	20.5	1.8
	VIII	22.8	17.7	0.5	41.0	20.7	17.1	20.4	19.5	0.7
	IX	7.6	0.1	4.1	11.8	19.5	15.5	11.5	15.5	0.3
	Total				2987

* coefficient was calculated according to the formula: $k=\frac{10P}{{\displaystyle \sum t}}$, where P is the sum of the monthly precipitation in mm, Σt is monthly total air temperature > 0 °C. Ranges of values of this index were classified as follows: extremely dry, 0.0 ≤ k < 0.4; very dry, 0.7 ≤ k < 0.4; dry, 1.0 ≤ k < 0.7; rather dry, 1.3 ≤ k < 1.0; optimal, 1.6 ≤ k < 1.3; rather humid, 2.0 ≤ k < 1.6; wet, 2.5 ≤ k < 2.0; very humid, 3.0 ≤ k < 2.5; extremely humid, 3.0 > k [17].

). The meteorological station was located 5 km south of the research point.

The Sielianinov hydrothermal coefficient, which is a measure of rainfall efficiency in a given month, best characterizes the course of the weather during the growing season. The description of pluviothermic conditions from May to September, i.e., during the period of the intense vegetation of potato plants in the studied area of Poland in 2016–2018, was developed on the basis of the value of the Sielianinov hydrothermal index (K). When assessing the hydrothermal conditions in the studied period, focus was placed on the frequency of the occurrence of atmospheric drought, which was determined on the basis of the value of the hydrothermal index K ≤ 1.0. The highest frequency of hydrothermal conditions in the classes fairly dry, dry, very dry, and extremely dry, i.e., with values of K ≤ 1.0, was observed most often in August and September, and the least frequently in July. In the remaining months, the values of the differences were varied, which proves the high dynamics of hydrothermal conditions in the Polesie Region in the analyzed period. The year 2016 was characterized by a drought in September. The years 2017–2018 can be described as moist in the first half and dry in the second half of the vegetation season. The climate of Poland is defined as moderate, transitory between the continental climate of the eastern part and the sea climate of the western part. The characteristic feature of the climate of Poland is high variability of the values of particular elements of the climate, including air and precipitation temperatures [17].

2.4. Soil Sampling

Before setting up the experiment each year, soil samples were collected from a 0–20 cm layer in 5 replications from each combination of the field experiment. The samples obtained were homogenized and then divided into 2 portions. The part intended for microbiological analysis in the wet state was sieved through a 2 mm sieve and then stored in closed plastic bags at 4 °C. The remainder of the sample was dried and, after sieving through a 2 mm sieve, was used for physical and chemical analysis of the soil. In each replication, the soil samples were taken from 5 different places from the arable layer (0–20 cm depth) using a Nekrasov auger [18].

2.5. Measurements of Physical and Chemical Properties

The granulometric composition of soil was determined by analyzing the particle size distribution with a laser diffractometer. The samples were air-dried, crushed in a porcelain mortar, and sieved with a 2 mm sieve [11]. The soil samples were analyzed for available phosphorus (P₂O₅) and potassium (K₂O) using the Egner–Riehm method; soil reaction pH was determined with a potentiometric method using a pH-meter in a 1 M KCl extract [19,20]; and the humus content was detected using the Tiurin method [21]. At the same time, these samples were subject to an analysis of organic C content, pH_KCl and pH_H2O, as well as mineral forms of nitrogen such as N-NH₄⁺ and N-NO₃⁻ [22,23].

The soil bulk density was used as a significant index of differences in the soil structure and moisture retentive measurements and was steadily measured from 50 mm diameter cores to a depth of 30 cm [24,25]. Soil cores were measured when wet, desiccated in an oven at 105 °C for 48 h, and measured once more to determine the soil moisture content and bulk density. Soil porosity was then determined from the bulk density as follows:

$$\mathrm{Total}\mathrm{porosity}=(1-\frac{\rho b}{\rho s}),$$

(1)

where ρb is the bulk density and ρs is the average particle density (2.65 g cm⁻³) [26].

2.6. Measurements of Biological Activities

In moist soil samples, parameters characterizing the microbiological profile of soils were determined, including soil enzymatic activity and the number of microorganisms, specifically the total number of bacteria, actinomycetes and fungi [26,27].

The soil obtained from the experiment was tested in triplicate for each combination of the field experiment and used to count the level of actinomycetes, bacteria and fungi. A total of 10 g of the soil samples was first immersed in 90 mL of deionized water; then, this combination was shaken for 10 min and left for 5 min. Following this, 1 mL of the supernatant was diluted two-fold and injected into water at a constant temperature of 30 °C. The levels of viable microorganisms were examined using the sequential dilution and casting procedure. Determination of the number of bacteria was carried out using the plate method on a substrate with soil extract, and the total number of fungi was detected with the plate method on the substrate of Martin [26]. Kenknight’s medium was used to count actinomycetes [27]. After observing the growth of microbial colonies in a favorable environment, the number of possible actinomycetes, bacteria and fungi was calculated (recorded as colony forming units (CFU)) per 1 g of soil dry weight [28]. The determination of the number of soil microbes was based on the method of plate dilution of the previously described methodology, at a temperature of 24 °C to 28 °C. Colonies of microorganisms grown on individual media were counted using a colony counter after 3–5 days [29].

The following activities were determined: Adh [30], AF [31,32], AU [29], and AP [33,34]. Adh activity was expressed in cm³ to determine the H₂ necessary to reduce TTC to TFP (triphenylphormosan); Afs—in moles of p-nitrophenol (PNP) formed from sodium 4-nitrophenylphosphate; AU—in mg of N-NH₄⁺ formed from hydrolyzed urea [29]; AP—in mg of tyrosine formed from sodium caseinate [32].

2.7. Physico-Chemical, Microbiological and Enzymatiacal Properties of Soil

Before testing, the soil was analyzed to determine granulometric composition, some physical characteristics and biological activity (

Table 4. Initial physico-chemical properties and microbiological and enzymatic activity of soil of the study site.

Sand (%)	Silt (%)	Clay (%)	Soil Textural Class	Bulk Density (MPa)	Porosity (%)	C:N Ratio
66.96	30.58	2.46	Sandy-loam	1.13	55.86	10.12
Initial numbers of bacteria, fungi and actinomycetes			Initial soil enzyme activity
Bacteria (×105 cfu·g−1 dry soil)	Fungi (×103 cfu·g−1 dry soil)	Actinomycetes (×104 cfu·g−1 dry soil)	Dehydrogenase [cm3H2·kg−1·d−1]	Phosphatase [mmol PNP kg−1·h−1]	Urease [NH4NO3+·kg−1·h−1]	Protease [mg tyrosine·kg−1·h−1]
2.88	0.09	5.54	1.32	6.69	6.76	8.38

Source: own research.

).

The sand, silt, and loam fractions indicated a granulometric subgroup—sandy loam (medium soil). The fraction of sand was 66.84%, the dust fraction was 30.70% and the percentage of loam was 2.45%. This proportion of individual fractions corresponds to the composition of clayey dust. In terms of agricultural suitability, these soils belong to a slightly acidic good rye complex. This soil is classified into the agronomic category of medium soil [30]. The bulk density of the studied soil was 1.13 MPa, while the porosity was 55.86% (Table 4). The presence of fungi, actinomycetes and soil enzymes at the beginning of the research is shown in Table 4. The results of the soil granulometric analysis and some physicochemical properties of soil in the years 2016–2018 are presented in

Table 5. The granulometric composition of soil.

Year	Composition Content of the Granulometric Fractions [%]			Soil Classification
	Sand 2.0–0.05	Silt 0.05–0.002	Loam <0.002
	mm
2016	66.91 a*	30.50 a	2.59 a	Sandy loam
2017	67.13 a	30.15 a	2.72 a	Sandy loam
2018	66.49 b	31.46 a	2.05 b	Sandy loam
Mean	66.84 a	30.70 b	2.45 c

Source: results of own experiments carried out at Chemical and Agricultural Station in Lublin. * The occurrence of the same letter pointer at averages (at least one) means that there is no statistically significant difference between them.

. The experiment was carried out on sandy loam soil. According to the sand, silt, and loam fractions, this is a granulometric subgroup, namely clay sand (medium soil).

The fraction of sand was 66.96%, the silt fraction was 30.58% and that of loam was 2.46%. All factions differed significantly from one another, while in particular years of the research the granulometric composition turned out to be homogeneous within the silt fraction (Table 5). This proportion of individual fractions corresponds to the composition of clayey dust. In terms of agricultural suitability, these soils belong to a slightly acidic good rye complex. This soil is classified in the agronomic category as medium soil [35].

2.8. Statistical Analyses

Statistical processing of results was carried out with a means of variance (ANOVA) model (SAS 9.2 2008) and regression analyses [36]. The significance of variability sources was verified using the “F” Fischer–Snedecor test, while the value of LSD₀.₀₅ was estimated using the Tukey test. The function parameters were determined using the least-squares method [37]. By performing t-Tukey’s multiple comparison tests, we were able to conduct detailed comparative analyses of averages by isolating statistically homogeneous medium groups (homogeneous groups) and determining the so-called least significant mean differences (LSD), which in Tukey’s tests are marked by HSD (Tukey’s Honest Significant Difference). The calculated p-values determine the significance and magnitude of the impact of the studied factors on the differentiation of the results of the analyzed variables, by comparing them with the most frequently accepted levels of alpha significance (0.05). In case of detailed analyses based on T Tukey’s multiple tests, the assumed significance level was α = 0.05. Letter indicators at averages determine the so-called homogeneous groups (statistically homogeneous). The occurrence of the same letter pointer at averages (at least one) means that there is no statistically significant difference between them [38].

3. Results

3.1. Abundance of Assimilable Nutrients in Soils and Humus

The soil abundance in available potassium and phosphorus, in studied soils before the experiment, was at a very low, low, or medium level. In general, the soil abundance in available components was higher in sustainable than organic production system (

Table 6. The content of available forms of soil potassium, phosphorus, magnesium, and humus.

Years	Content of K2O [mg·100 g−1]		Content of P2O5 [mg·100 g−1]		Content of MgO [mg·100 g−1]		Humus [g·kg−1]
	E *	S **	E	S	E	S	E	S
2016	5.8 a***	7.8 b	10.5 a	14.9 b	7.3 a	8.0 b	1.47 a	1.48 a
2017	5.2 b	10.1 a	4.5 b	15.5 a	7.2 a	8.2 a	1.43 a	1.49 a
2018	5.1 b	10.9 a	3.8 b	15.8 a	7.0 b	8.3 a	1.41 a	1.57 a
Mean	5.4 b	9.6 a	6.3 b	15.4 a	7.2 b	8.2 a	1.44 a	1.51 a

* E—organic system; ** S—sustainable system; *** The occurrence of the same letter pointer at averages (at least one) means that there is no statistically significant difference between them.

).

In 2018, the soil abundance in available potassium in the organic system, which is a basic nutrient for potato, was only 5.8 mg K₂O, while two years later this was 5.1 mg K₂O per 100 g⁻¹ of soil, which is a very low value. The reason for this low potassium content in the soil, in this system, was the dissipation of large amounts of the element along with the clover-grass yield. In the case of phosphorus, soil depletion was also observed in the organic system, up to the lower limit of the average abundance. Soil abundance in bioavailable magnesium was high, although this was lower in the organic system compared to the sustainable farming system. The content of humus in the tested soil was similar and present at low levels, with oscillations from 1.47% in the organic system, in 2018, to 1.41% in 2018; however, its content was higher in the sustainable management system (Table 6).

3.2. Physico-Chemical Properties of Soil

The levels of carbon and humus helped to estimate the content of organic matter in the soil, as well as the degree of its humification. The C content in the tested soil was not differentiated by farming systems, pre-germination, nor years of research; rather, the only difference was the cultivars used. Most of this element was found in soil under the cultivation of late ‘Tajfun’ cv., while the lowest level of this element was detected under the cultivation of very early ‘Denar’ cv.; additionally, the cultivars ‘Denar’ and ‘Gwiazda’, and ‘Satina’ and ‘Jelly’ proved to be homogeneous in terms of the value of this trait (

Table 7. Physical and chemical properties of soil under cultivation of potato.

Experimental Factors		C [g·kg−1]	Total N [g·kg−1]	C:N Ratio	N-NO3− [mg·kg−1]	N-NO4+ [mg·kg−1]	pHKCl	pHH20
System of Tillage *	E	11.15 a***	1.08 a	10.35 a	23.98 a	30.29 a	5.28 a	6.15 a
	S	10.43 a	0.97 b	10.78 b	26.02 b	33.19 b	5.48 b	6.25 a
Cultivars	‘Denar’	10.41 c	0.94 b	11.11 a	17.98 e	29.69 d	4.68 d	5.65 cd
	‘Gwiazda’	10.44 c	0.98 b	10.65 ab	25.62 c	30.64 c	5.45 ab	6.33 ab
	‘Satina’	10.62 abc	0.98 b	10.80 ab	25.03 c	31.71 b	5.03 c	5.73 cd
	‘Jelly’	10.74 abc	1.06 a	10.12 b	30.69 a	35.32 a	5.38 ab	6.15 ab
	‘Jurek’	10.93 ab	1.08 a	10.10 b	22.21 d	31.34 b	5.85 a	6.73 a
	‘Tajfun’	11.60 a	1.11 a	10.49 bc	28.49 b	31.74 b	5.90 a	6.63 a
Pre-planting treatments **	A	10.77 a	1.00 a	10.77 a	25.42 a	31.69 a	5.45 a	6.23 a
	B	10.88 a	1.05 a	10.32 a	24.58 a	31.79 a	5.31 a	6.18 a
Years	2016	10.77 a	1.02 a	10.55 a	25.01 a	32.12 a	5.28 b	6.15 b
	2017	10.82 a	1.05 a	10.37 a	24.91 a	31.92 a	5.64 a	6.70 a
	2018	10.77 a	1.03 a	10.78 a	25.08 a	31.18 a	5.23 b	5.79 c

* System of tillage: E—organic system, S—sustainable system; ** Pre-planting treatments: A—unsprued potato; B—sprued of potato; *** The occurrence of the same letter pointer at averages (at least one) means that there is no statistically significant difference between them.

). The total N content was significantly higher in the organic system than in the sustainable management system. Under the influence of mineral fertilization used in the sustainable system, including fertilization with N, the C: N ratio also increased. The highest content of N was found in the soil under the cultivation of late ‘Tajfun’ cv., while the lowest was found under the cultivation of very early ‘Denar’ cv. The cultivars ‘Denar’, ‘Gwiazda’ and ‘Satina’, and ‘Jelly’, ‘Jurek’ and ‘Tajfun’ proved to be homogeneous in this respect (Table 7). The soil samples revealed significantly higher ammonification activity determined by the amount of accumulated ammonia N in the sustainable than the organic system (Table 7). Among the studied potato cultivars, the highest ammonification activity was observed in soil samples from medium late ‘Jelly’ cv., whereas the lowest was found in very early ‘Denar’ cv. According to the values of this feature, the tested cultivars can be arranged as follows: ‘Jelly’ > ‘Tajfun’ > ‘Gwiazda’ > ‘Satina’ > ‘Jurek’ > ‘Denar’; although, the ammonification activity of ‘Gwiazda’ and ‘Satina’ cv. appeared to be uniform. The relatively small differences in the amount of this N formed in soil samples under pre-germinated and non-germinated potato cultivation can be explained by the fact that probably organic N compounds contained in remnants of red clover or in the compost used as a fertilizer, underwent ammonification throughout the season. The higher activity of nitrate, determined as an amount of accumulated nitrate N, was recorded in the sustainable crop production system as opposite to organic production (Table 7). Significant differences in the amount of accumulated N formed were also found in soil samples under tested cultivars. The highest content of nitrate N was found in samples collected from ‘Jelly’ cv., whereas the lowest was found in very early ‘Denar’ cv. The ‘Satina’, ‘Jurek’ and ‘Tajfun’ cultivars proved to be homogeneous in this characteristic. Germination of seed potatoes did not significantly differentiate the form of N in the soil under potato cultivation. The levels of ammonia and nitrate N accumulation in the soil under the cultivation of potato in different years were similar.

The analyzed soil was characterized by a pH from acidic to slightly acidic, depending on the test objects (pH_KCl 5.38 with fluctuations from 4.68 to 5.90, pH_H2O 6.21, with fluctuations of 5.65–6.73) (Table 7). The sustainable farming system was characterized by higher values of pH in KCl, as compared with the organic system. A significant difference in the soil acidity under the influence of a cultivar was also found. The lowest pH_KCl value was recorded in soil samples under very early ‘Denar’ cv., whereas the highest was recorded for late ‘Tajfun’ cv. The soil acidity of samples under ‘Gwiazda’ and ‘Jelly’ cv. and ‘Jurek’ and ‘Tajfun’ cv. did not differ significantly in terms of this feature value. The lowest pH_H2O value was recorded in soil samples under ‘Denar’ cv., whereas the highest was recorded under late ‘Jurek’ cv. The soil acidity of samples under ‘Gwiazda’ and ‘Jelly’ cv.; ‘Denar’ and ‘Satina’ cv.; and ‘Jurek’ and ‘Tajfun’ cv. did not differ significantly in terms of this feature value. Pre-germination of seed-potatoes and habitat conditions during the years of study did not exert any significant effect on the acidity of the soil. The lowest soil pH value, both in KCl and H₂O, was recorded in 2018, while the highest values of this trait were obtained in 2017 (Table 7). Pre-planting treatments had no effect on any of the examined features of soil (Table 7).

3.3. Microbial Activity of Soil

Soil tillage systems significantly affected bacteria, fungi and Actinomycetes at the measured soil depth (i.e., 0–20 cm) (

Table 8. Influence of experimental factors on actinomycetes, bacteria and soil fungi.

Experimental Factors		Actinomycetes (×104 cfu·g−1 Dry Soil)	Bacteria (×105 cfu·g−1 Dry Soil)	Fungi (×103 cfu·g−1 Dry Soil)
Initial numbers of actinomycetes, bacteria and fungi–before starting the experiment in spring 2016
		2.88	0.09	5.54
Numbers of actinomycetes, bacteria and fungi–after the experiment
System of tillage *	E	4.50 a***	3.78 a	0.18 a
	S	2.88 b	2.22 b	0.10 b
Cultivars	‘Denar’	3.2 de	2.56 cd	0.07 e
	‘Gwiazda’	3.29 de	2.58 cd	0.10 d
	‘Satina’	3.78 bc	2.85 c	0.12 bc
	‘Jelly’	3.77 bc	3.22 ab	0.14 bc
	‘Jurek’	3.95 ab	3.34 ab	0.18 a
	‘Tajfun’	4.16 a	3.46 a	0.20 a
Pre-planting treatments **	A	3.56 b	2.95 b	0.12 b
	B	3.82 a	3.05 a	0.16 a
Years	2016	4.73 a	4.45 a	0.21 a
	2017	2.79 c	2.04 c	0.08 c
	2018	3.56 b	2.53 b	0.13 b

* System of tillage: E—organic system, S—sustainable system; ** Pre-planting treatments: A—unsprued potato; B—sprued of potato; *** The occurrence of the same letter pointer at averages (at least one) means that there is no statistically significant difference between them.

). In the organic system, without the use of mineral fertilizers, with limited use of plant protection products, a significantly higher number of all analyzed soil microorganisms was recorded, compared to the sustainable system, where mineral fertilization and chemical plant protection products were used. The genetic factor also had a significant role in shaping the number of soil microorganisms.

The soil under cultivation on the late cultivars was typically characterized by a higher number of microorganisms tested, compared to the soil under the cultivation of very early and early potato cultivars. The highest abundance of Actinomycetes, bacteria and fungi in the root rhizosphere was noted by the late ‘Tajfun’ cultivar, while the lowest was observed in very early ‘Denar’ cultivar. When the soil was colonized by Actinomycetes, the ‘Satina’ and ‘Jelly’ cultivars as well as ‘Denar’ and ‘Gwiazda’ proved homogeneous in terms of the value of this trait. Concerning colonization of the rhizosphere by bacteria, the very early ‘Denar’ cv., as well as the early ‘Gwiazda’ cultivar proved to be homogeneous in terms of this feature, i.e., they created similar conditions for bacterial growth in the soil medium. In the case of colonization of fungi in the medium, all the tested cultivars differed significantly due to their abundance. They were least observed in the soil where the very early ‘Denar’ cultivar was grown, and the other cultivars can be ranked as follows: ‘Gwiazda’ < ‘Satina’ < ‘Jelly’ < ‘Jurek’ < ‘Tajfun’ (Table 8). Generally, a longer vegetation period of potato cultivars contributed to an increase in the number of bacteria, fungi and actinomycetes in the soil. Germination of seed potatoes, by eliminating tubers infected with diseases before planting, also significantly affected the settlement of the soil under potato cultivation for all tested groups of microorganisms, compared to the control without the germination of the tubers before planting (Table 8). Meteorological conditions in the years of research significantly differentiated the composition and abundance of soil microflora. In 2018, with the highest rainfall observed during the most intense tuber growth (June, July), the largest number of microorganisms tested in the arable soil layer was observed (Table 8). Their smallest number was recorded in during the dry period of 2017, where as much as 5 months of vegetation (April, May, June, August, and September) soil drought occurred and the average air temperature in May, June, July, and August was higher than the average temperature during the years 1980–2014 (Table 8).

3.4. Enzymatic Soil Activity

The results show a clear change in the enzymatic activity of the studied soil under the influence of crop production systems (

Table 9. Enzymatic activity of soil under cultivation of potato.

Experimental Factors		Dehydrogenase [cm3H2·kg−1·d−1]	Phosphatase [mmol PNP kg−1·h−1]	Urease [mg NH4NO3+·kg−1·h−1]	Protease [mg tyrosine·kg−1·h−1]
Initial soil condition of the study site—Soil enzyme activity before starting the experiment in spring 2016
		1.32	6.69	6.76	8.38
Soil enzymatic activity after the experiment
System of tillage *	E	1.26 b**	6.59 b	6.80 a	8.15 b
	S	1.34 a	6.97 a	6.84 a	8.71 a
Cultivars	‘Denar’	1.21 b	5.63 e	6.78 cb	7.43 c
	‘Gwiazda’	1.23 b	7.26 b	6.58 c	8.01 b
	‘Satina’	1.39 a	6.29 d	7.96 a	8.48 b
	‘Jelly’	1.41 a	7.75 a	7.02 b	10.08 a
	‘Jurek’	1.24 b	7.28 b	6.31 d	8.31 b
	‘Tajfun’	1.14 c	6.49 c	6.26 d	8.26 b
Pre-planting treatments **	A	1.26 a	6.93 a	6.87 a	8.31 b
	B	1.27 a	6.64 a	6.76 a	8.54 a
Years	2016	1.29 a	6.72 a	6.79 a	8.43 a
	2017	1.28 a	6.85 a	6.78 a	8.40 a
	2018	1.24 a	6.78 a	6.88 a	8.46 a

* explanations as Table 7; ** The occurrence of the same letter pointer at averages (at least one) means that there is no statistically significant difference between them.

).

The activity of Adh, AF, and AP was significantly higher in sustainable than organic systems. In the case of AU, agricultural production systems did not have a major effect on the enzymatic activity. The increase in enzyme activity was accompanied by an increase in the C:N ratio as well as an increase in the content of mineral N forms of N-NH₄⁺ and N-NO₃⁻ along with the increase in pH_KCl of soil. Cultivars, from which the soil samples were collected, proved to be the greatest factor differentiating the activity of soil enzymes (Table 9). The highest activity of Adh, AFs, and APs was found in the soil from under the medium late ‘Jelly’ cv. while that of AU was found in soil from under the medium early ‘Satina’ cv. Both the potato vernalization treatment and soil and climatic conditions in the years of the study failed to modify the enzymatic activity (Table 9).

4. Discussion

The accumulation of organic C in mineral soils is favored by periods of high and low activity of microorganisms in the soil; therefore, mineralization processes prevail in the humification process in our climate zone. Hence, the content of humic substances was low [14,38,39,40,41]. The studies showed that crop production systems determined the formation of enzymatic activity and chemical properties of the soil under potato cultivation. Different forms of fertilization (organic, mineral) and the doses of fertilizers applied in both farming systems caused significant changes in enzymatic activity and chemical properties of the soil. Higher Adh activity in the soil under the cultivation of potato in the sustainable system could result from the higher concentration of root exudates produced by the root system of the crop [39]. In the opinion of Tarafdar and Classen [40], root exudates are a perfect source of nutrients for microorganisms, in particular within the rhizosphere. In turn, according to Januszek et al. [41], Adh activity in the soil, regarded as a measure of total microbial activity, is not related to the total number of microorganisms in the soil. Their activity in the soil may be subject to errors due to other oxidoreductases. They are present in the soil and affect plants, as they are capable of reducing TTC and not participating in electron transport, the presence of nitrate in the soil, Fe²⁺ compounds and the content of organic compounds such as catechol [42,43]. Bremner and Tabatabai [44] concluded that nitrates and iron have an inhibitory effect on the activity of Adh, whereas iron and manganese oxide, sulfates, phosphates, and chlorides cause an increase in their quantity. One of the conditions of enzymatic activity determination is to provide an optimal pH for each enzyme. The maximum Adh activity was recorded by Brzezińska et al. [45] in situ at a pH ranging from 6.6 to 7.2. Trevors [46] found that Adh activity decreases along with lowering the soil pH. Research conducted by von Mersi and Schinner [47] reveal that the optimum activity of Adh occurs at pH 7.0–7.5. In the opinion of Januszek et al. [41], due to the possibility of the chemical reduction of TTC in soils, Adh activity should be compared in soils under similar organic conditions.

AFs play a key role in soil, as they stimulate the conversion of organic compounds of phosphorus into inorganic phosphates (HPO₄⁻² and H₂PO₄⁻), which are directly available to plants and soil organisms. In this study, AF activity was significantly higher in the sustainable crop production system, with full organic and mineral fertilization, as compared with the organic system, which used full organic fertilization, but incomplete mineral nutrition. Different results were achieved by Flis-Bujak et al. [7], who claim that supplying fertilizers to the soil may reduce the activity of certain enzymes, e.g., elevated levels of inorganic phosphorus in the soil decreases the activity of AF. The enzymatic activity of AU can be reduced by the addition of increased doses of fertilizers containing ammonium compounds. AF activity, in the opinion of Bielińska [30] and Yan et al. [48] is associated with the soil and vegetation conditions, and it reacts to changes in soil management. Lemanowicz [49] showed a significant positive correlation of available phosphorus with soil properties such as total organic C. AU activity was not significantly dependent on the cultivation system. The research of Flis-Bujak et al. [7] showed that the activity of this enzyme is associated with the tillage system and is the lowest in monoculture. Lloyd [31] suggests that AU activity is associated with the content of organic substances in soil and may be an element limiting the soil complex which protects it against the effects of AP enzymes. Studies by Bielińska et al. [3] revealed that the activity of soil enzymes is lower in soils cultivated traditionally than in soils managed using a simplified scheme. Traditional farming, by changing the vertical distribution, chemical composition, and particle size of organic matter, as well as water and air conditions in the soil environment, affects both the enzyme activity and microbial biomass. According to Tarafdar and Classen [40], plants are characterized by variable amounts of a direct use of inorganic phosphorus, since phosphorus from organic compounds must be hydrolyzed with the participation of soil AFs, the main producers of which are the soil microorganisms and fungi. Plants uptake available phosphorus through the root system. Soil AF activity significantly decreases with increases in the mineral phosphorus content. Mineral N fertilization, according to Lemanowicz [49], results in only small changes in the activity of AF and the phosphorus fraction content. Our study showed a dependence of AFs on the crop production system, which differ, among others, with the size of mineral fertilization and pesticides application.

Enzymatic activity in soils is determined by many factors. These include, among others, organic matter content, soil pH, the content of biogenic elements, abundance, and the species composition of microorganisms [50]. Šimek and Hopkins [51] believe that there is a simple relationship between the pH of the soil and the DEA and DP, and that reduced soil pH leads to a reduction in denitrification and vice versa. The effects of artificially increased pH to a value close to 6.3 by adding NaOH to the soil, greatly increased the DEA, DP, and RESP. The optimum pH level for DP was between 7 and 8. Nazarkiewicz and Kaniuczak [52], when studying the influence of liming and mineral fertilization on enzymatic activity of a lessive soil developed from the loess, found that liming increases the enzymatic activity of Adh and AFs, while mineral fertilization reduces the activity of Adh and APs. Furthermore, these authors showed a positive effect of liming interaction with mineral fertilization on the enzymatic activity of Adh, AF’s, and AP’s in limed soil. According to Koper et al. [53], Wyczółkowski et al. [14], and Yang et al. [33] various agricultural practices, such as correct crop rotation, level, and type of fertilization, species, and cultivar of crops, are also factors that have a significant effect on enzymatic activity, and thus on soil fertility.

All changes in biogenic substances occurring in the soil are stimulated by enzymes conditioning their conversion into forms available to plants and microorganisms. According to Pszczółkowski and Sawicka [54], the soil enzymes may be useful as “indicators of fertility” of the soil. They help to estimate the availability of nutrients in soils. For this purpose, it is proposed to determine the Adh and various AFs and deaminases, e.g., asparaginase and AU activities. Their activity depends on the content of organic matter in the soil. The presence of certain compounds in the soil will stimulate or inhibit the synthesis of a given enzyme without affecting the overall life of the soil microorganisms. Extracellular soil enzymes, when bound to colloids, may be less sensitive to external factors than the live cells of microorganisms. Mijangos et al. [55] concluded that Adh activity is the most sensitive to tillage, while conventional physicochemical parameters are insufficiently sensitive in detecting relatively slight changes in soil properties under the influence of agricultural practices in a short period of time. In the opinion of Lemanowicz [49], changes in the soil abundance in N and its physicochemical properties are mainly caused by N fertilization which increases the population of bacteria, actinomycetes, and fungi. Excessively high doses of this nutrient may in fact lead to the accumulation of ammonia that intoxicates plants and limits the growth of certain groups of microorganisms; this also affects the decrease in soil pH, which is important for the activity of enzymes [45,46,47]. Such a dependence was also confirmed in this study. According to Yang et al. [33], and Dong et al. [56], different fertilizers may affect the enzymatic activity of soil and the dynamics of its fertility. Soil enzymatic activity, in their opinion, measured by the activity of AF, catalase, AU, and invertase, decreases in the initial growth stage of the crop, but increases along with the provision of nutrients from decomposing manure, or plowed intercrop biomass to the plants, because mineral N inhibits the enzymatic activity of soil, but P and K contained in fertilizers complement it.

The organic C content in soil consists of a heterogeneous mixture of substances containing C—both simple and complex [57]. The sources of organic matter are crop residues, plant-origin and animal-origin fertilizers, compost, and other organic substances. The increase in enzyme activity was accompanied by an increase in the C:N ratio as well as an increase in the content of mineral N forms of N-NH₄⁺ and N-NO₃⁻ along with the increase in the pH_KCl of soil. Spohn et al. [58] state that microbial respiration per unit of microbial biomass depends on the litter layer carbon-to-N ratio. The observed downward trend in organic matter content in the organic system, as it may be assumed, results from the limited presence of decaying organisms, or a greater degree of degradation due to changes in natural or anthropogenic factors. Organic matter is an essential component of a “healthy” soil; thus, a reduction in its content leads to soil degradation [38].

Potato cultivars grown in the studied soil exerted a major influence both on the enzymatic activity and chemical characteristics of the soil. Greater amounts of N, C, ammonium, and nitrate N were accumulated by late compared to early cultivars, which is associated with the length of the vegetation period for these cultivars. The highest activity of Adh, AFs, and APs was recorded in the soil under the cultivation of medium late ‘Jelly’ cv., while that of AU was recorded under the cultivation of medium early ‘Satina’ cv., which can be explained by higher concentrations of root exudates produced by the root system, that are a great source of nutrients for microorganisms, especially in the rhizosphere, which is confirmed by Landi et al. [59], Spohn et al. [58], and the studies in [60,61,62,63,64]. According to Deng [62] and Peng et al. [63], the excessive fertilization of potato leads to an excess of nitrogen in the soil, and the excess of nitrogen, in turn, leads to the balancing and limitation of urease activity by effective components of ammonium nitrogen in fertilization and to the enzyme product [62]. In turn, the excess of phosphate fertilizer, as stated in [64,65], inhibits not only the hydrolysis of phosphorus-containing compounds, but also soil microorganisms and the synthesis of phosphatase under the root.

The organic system led to a higher number of actinomycetes, bacteria and fungi in the soil compared to the sustainable farming system. Research by Martyniuk et al. [15] reveals that the higher soil acidity in the organic than conventional farming system, is the factor favoring the better development and activity of soil microorganisms. Konrad et al. [60] and Despotovic et al. [61] found that the scale of farm operations and environmental concerns are especially important for farmers. The soil in the organic system is characterized by a more favorable reaction, mainly because of the improved balance of organic matter, among other factors, as a result of the two-year growing of grass mixtures with legumes and removing the mineral fertilizers in this system [62,66,67,68,69]. The correct soil structure and its fertility are determined by the increased biological activity of the soil, i.e., proper development, number and species composition of microorganisms, as well as their enzymatic activity. Such action creates favorable conditions for the germination of seeds or seed potatoes, as well as for the proper development of the root system of crops, which is an indispensable factor in obtaining high yields [69,70].

Supplementing the basic physico-chemical tests of soil with the assessment of microbiological activity will lead to the development of suitable plant cultivation technologies, while considering the needs of the soil environment. Soil is the basis for the functioning of ecosystems, which is why it is important to measure and monitor changes in it in order to optimize the use of its resources [69,70,71].

Our research emphasizes the importance of the impact of the rhizosphere on the content of nutrients in the soil, and the activity of enzymes in arable soils. More research is needed to understand specific processes in the rhizosphere in order to obtain adequate rhizosphere biotechnology to restore the natural ecosystem. Sprouting seed potatoes did not have a significant effect on any of the soil quality indicators. Pre-planting treatments had no effect on any of the examined features of soil, but the quality of the soil, its preparation before planting, temperature and soil moisture, and its biological activity affect the speed and uniformity of plant emergence and, consequently, the potato yield. According to Filipović [72], the biggest challenge of today’s agriculture is to ensure a sufficient water demand in the key phase of plant development and to use the available moisture in the soil through the rhizosphere system. The improvement of soil moisture management, according to this author, should focus on supporting environmental, food, social and economic security within a sustainable ecosystem.

5. Conclusions

Every studied crop production system exerted different impacts on the soil quality. The sustainable system of cultivation, with the application organic and mineral fertilizations and the comprehensive protection against diseases, pests, and weeds, contributed to the increasing enzymatic activity of Adh, AF’s, and AP’s; the improvement in the soil abundance in available phosphorus, potassium, and magnesium; the increased humus content in the soil; the improvement of soil pH; and the increase in the content of mineral N forms. On the other hand, this system also contributed to the reduction in the content of C and total N, thus extending the C:N ratio and to the decreasing number of bacteria, fungi and Actinomycetes in the soil under the cultivation of potato. Organic cultivation resulted in changes in the chemical properties of the soil by the increase in the content of organic C, and total N, and thus, narrowing the C:N ratio, leading to a reduction in the content of mineral N forms, increasing the acidity of the soil, reducing the enzymatic activity of Adh, AFs, and APs, but also to increasing numbers Actinomycetes, bacteria and fungi in the soil. Pre-germination of seed-potatoes contributed to the increase in total N and nitrate N in the soil, to extend the C:N ratio and an increase in the number of actinomycetes and fungi in the soil under potato cultivation. Cultivation of the studied potato cultivars had a major impact on the chemical characteristics and enzymatic activity of the soil. The highest enzymatic activity, as well as the highest content of mineral N forms, was recorded in soil, where medium late cultivar ‘‘Jelly’’ was grown. The highest contents of organic C, total N and highest number of Actinomycestes, bacteria and fungi were determined in the soil under the cultivation of late cultivar ‘Tajfun’. Determination of the soil enzymes’ activity in the organic and sustainable systems, indicated the usefulness of these types of assays as sensitive indicators of the response of soil to different management strategies in crop production.