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Article

Soil Organic Carbon Dynamics in the Long-Term Field Experiments with Contrasting Crop Rotations

by
Tomáš Šimon
,
Mikuláš Madaras
*,
Markéta Mayerová
and
Eva Kunzová
Crop Research Institute, Department of Crop Management Systems, 161 06 Prague, Czech Republic
*
Author to whom correspondence should be addressed.
Agriculture 2024, 14(6), 818; https://doi.org/10.3390/agriculture14060818
Submission received: 20 March 2024 / Revised: 29 April 2024 / Accepted: 22 May 2024 / Published: 24 May 2024
(This article belongs to the Special Issue Soil Management for Sustainable Agriculture)
Browse Figures
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Abstract

:
Trends in soil organic carbon (SOC) were analyzed in the soils from the oldest Czech long-term field experiment, the Prague-Ruzyně Long-Term Fertilizer Experiment, conducted on Haplic Luvisol since 1955. The aim of the work was to compare the long-term dynamics of SOC in contrasting crop rotations and different fertilization regimes. The trial design includes two crop rotations (CR): simple CR with two-year rotation of sugar beet and spring wheat, and multi-crop rotation (MCR) with nine crops. Four fertilization treatments were chosen for SOC analysis: unfertilized control, only mineral fertilization (NPK), farmyard manure application (FYM), as well as FYM and NPK application. SOC content was significantly affected by both fertilization and crop rotation practices. In the simple CR, both the unfertilized control and the NPK treatment exhibited a consistent decline in SOC content over the study period, with percentages decreasing from an initial 1.33% in 1955 to 1.15% and 1.14%, respectively. Although the FYM and FYM + NPK treatments showed an increase in SOC content in the 1990s, a gradual decline was recorded in the last two decades. This decrease was not observed in MCR: positive C balances were recorded in all treatments within MCR, with the largest increase in SOC stock occurring when NPK was combined with FYM. In contrast, over the last decade, C balances have decreased in simple CR for all treatments except FYM. This trend coincides with changes in the local climate, particularly rising temperatures. The results indicate that diversified crop rotations and FYM fertilization are effective in mitigating the negative impacts of changing environmental conditions on SOC stocks.

1. Introduction

Soil organic matter (SOM) determines soil fertility, regulates most soil functions, and controls the productivity of agricultural soils. Under stable environmental conditions and agronomy practices, soil organic carbon (SOC) stocks are in a dynamic balance between carbon (C) inputs, mainly in the form of crop residues and organic fertilizers, and C loss due to decomposition of SOM [1]. Long-term field experiments conducted at Rothamsted Experimental Station showed that SOM does not increase above the certain equilibrium level specific to the local conditions of soil type, cropping, and fertilization. These changes often occur slowly in temperate climates [2]. However, with ongoing climate change accompanied by rising temperatures and changes in precipitation and the soil moisture regime, the balance between organic inputs and their decomposition may change.
Some recent studies suggested that the content of SOC in European agricultural soils was declining [3]. The rate of change appears to be proportional to the initial SOC content. SOC changes in the topsoil of Swiss cropland at well-defined monitoring sites every five years from 1990 to 2014 were studied in [4]. SOC remained stable for the set of monitoring sites, although increasing and decreasing trends ranging from −11 to +16% relative change per decade were observed for individual sites. An average −0.29 t C ha−1 year−1 loss of SOC stocks was found in Swiss long-term field experiments, where permanent grasslands tended to lose less or even gain SOC (0.09 t C ha−1 year−1 in average) compared to croplands, with an average loss of −0.34 t C ha−1 year−1 [5].
Bogusz et al. [6] studied SOC content in Polish soils from 2015 to 2021, examining its relationship with agronomic categories and drought intensity. The analysis concentrated on mineral soils, encompassing a wide range of soil textures. Soil samples were collected from 1011 farms, with C content ranging from 0.85% to 2.35%. The analysis revealed that fluctuations in C content were largely influenced by soil management practices and the occurrence of drought during the study period. It was noted that soil moisture conditions significantly impacted the C accumulation. In areas affected by drought, a decrease in SOC content was observed. Szatmári et al. [7] predicted the SOC stock change between 1992 and 2010 in Hungarian soils at various aggregation levels. The total SOC stock in the topsoil was reported at 424.41 Tg in 1992 and 451.59 Tg in 2010. In areas where land use types remained unchanged, it was observed that the SOC stock increased under forests by 16.29 Tg and under pastures by 2.48 Tg, while it decreased under wetlands by 0.49 Tg. No change in SOC stock was noted under agricultural areas.
Management practices, including various tillage systems, significantly influence the quantity of SOC and composition of SOM. Traditionally, tillage has been used to mechanically prepare soils for seeding and to minimize the negative effects of weeds. The impact of tillage on SOC has been extensively reviewed by several authors. These reviews and meta-analyses have demonstrated both beneficial effects on SOC from no-tillage practices compared to conventional tillage [8,9], as well as null effects, indicating no significant difference between the two methods [10,11]. Shen et al. [12] demonstrated that no tillage and deep plowing have positive effects on soil aggregate stability and labile C fractions, enhancing SOC and dissolved and particulate organic C contents. In recent years, less intensive tillage practices and no tillage agricultural management have been promoted to mitigate negative impacts on soil quality and to preserve SOC [13].
To assess the impact of climate change on SOC, it is crucial to have access to long-term series of C measurements, as well as precise data on weather conditions and management practices, such as fertilization at specific sites. On the basis of these data, trends in soil C dynamics are being intensively modeled, both at local and global levels. Using global-scale modeling, Hertzfeld et al. [14] found that global cropland SOC stocks decline until the end of the century by only 1.0% to 1.4% if residue retention management systems are generally applied and by 26.7% to 27.3% in the case of residue harvest. Bruni et al. [15] analyzed data from 11 long-term experiments involving the addition of exogenous organic matter to estimate the amount of C input needed to reach the 0.1 and 0.4% SOC stock increase. They found that to reach this increased target relative to the onset of the experiment, 2.51 and 2.61 t C ha−1 year−1 of additional C input was necessary, respectively.
Long-term field experiments are used to evaluate the long-term dynamics of SOC in the Czech Republic, as well as in Europe. For example, Balík et al. [16] showed an increase in SOC content of 19% on Luvisol and 15.9% on Chernozem due to the application of farmyard manure in field experiments lasting more than 20 years. Similarly, the authors of [17] demonstrated an increase in SOC due to farmyard manure or farmyard manure with mineral fertilizers compared to the unfertilized control based on 13 long-term experiments. In addition to the effect of organic fertilization, crop rotation (CR) influences SOC stock. Higher crop species diversity in CR than continuous crop monoculture changed the quantity and quality of residue-derived C input into soil systems [18]. The global synthesis revealed that CR overall enhanced SOC content by 6.6% compared to monocultures. SOC content under CR increased more in regions with intermediate mean annual temperature (8–15 °C) and precipitation (600–1000 mm) than in regions with other climate types [19].
The aim of this study is to assess and discuss the dynamics of the SOC content in the soils of the oldest Czech long-term field experiment on Luvisol—the Prague-Ruzyně Long-Term Fertilizer Experiment (RFE). Contrasting fertilization treatments and crop rotations were selected. Consistent with results of numerous studies, we hypothesize that the rate and dynamics of SOC content and resulting C sequestration are predominantly shaped by crop structure and fertilization practices, with notable modulation attributed to evolving climatic factors. Our research focus lies in investigating the extent of this modulation, particularly discerning the direction and rate of SOC changes under combinations of fertilization and crop rotation.

2. Materials and Methods

The study site is located in Prague-Ruzyně, the Czech Republic (latitude 50°05′15″ N, longitude 14°17′27″ E). Altitude of the site is 370 m a.s.l. The long-term temperature norm for the period 1961–1990 is 8 °C, and for 1991–2020 is 9.6 °C. The long-term precipitation norm for the period 1961–1990 is 427 mm, and for 1991–2020 it is 497.5 mm.
The taxonomical soil unit is Haplic Luvisol, clay loam, developed on diluvial sediments mixed with loess (plough layer properties—sand content: 14%, silt: 59%, clay: 27%, pH/KCl = 5.8–7.1, plant available P: 12–100 mg kg−1, and plant available K: 160–250 mg kg−1).
The RFE was established in 1955 with the objective of studying the effects of various fertilization systems on crop yields, nutrient uptake, and soil quality. The experiment comprises several blocks that differ in crop rotation systems and employ a combination of mineral and organic fertilization. A detailed description of the trial design is presented in [20,21]. Two blocks with different crop rotations were chosen for the study.
Field B—simple crop rotation (SCR) with only two crops: sugar beet and spring wheat. It includes 19 treatments in 4 replications (96 individual plots), and the plot size is 12 × 12 m. Four fertilization treatments were selected for the study: control—unfertilized since 1955, NPK—only mineral fertilization, FYM—farmyard manure (25% dry matter and 0.5% N content), 21 t ha−1 each second year before sugar beet, and NPK + FYM.
Field IV—multi-crop rotation (MCR) with nine-year crop rotation: alfalfa/alfalfa/winter wheat/sugar beet/spring barley/potato/winter wheat/sugar beet/spring barley under sown with alfalfa. It was designed the same as SCR. Four fertilization treatments were selected: control—unfertilized since 1955, NPK—only mineral fertilization, FYM—farmyard manure, 21 t ha−1 before sugar beet and 15 t ha−1 before potato, and NPK + FYM (Table 1).
In both blocks of the trial, most crop residues were removed after harvest. Field trial management involved mold-board ploughing to a depth of 20–25 cm, followed by standard seedbed preparation and sowing procedures.
From each treatment, one of four experimental plots was sampled annually, except some years when sampling was omitted. Soil sampling was carried out before mineral fertilization at the beginning of April in the periods 1970–2022 (SCR) and 1990–2022 (MCR) from topsoil at depths of 0–20 cm at four points of each individual plot. Partial soil samples were combined in 2 kg lots, homogenized, air-dried at room temperature, and run through a 2 mm sieve. SOC content in current and archived soil samples was measured by dry combustion using a Vario MAX CNS/CN analyzer (Elementar Analysensysteme GmbH, Hanau, Germany).
The SOC stock in the soil plough layer (0–20 cm) was calculated using the equivalent soil mass (ESM) method [22]. For calculations, a uniform bulk density of 1.35 g cm−1 (typical for studied soils) was considered, as multiple occasional measurements at the time of soil sampling did not confirm statistically significant differences in bulk density between the treatments (unpublished data). C sequestration was calculated as the difference between the actual SOC stock of individual treatments and the (calculated) original SOC stock at the beginning of the experiment.
Although the experiment started in 1955, SOC data collection began much later. Therefore, comprehensive analysis was performed to estimate the initial soil C content at the experimental site based on the observed patterns [23]. This task required trend modeling and the estimation of experimental effects of the block (field), plot of the block, and standardized year, corresponding to the position in the crop rotation of the block. The model assumed that the effects were additive with respect to the soil C content. Baseline soil C contents of 1.33% for SCR (95% probability within the interval 1.29–1.36%) and 1.29% for MCR (1.23–1.37%) were estimated by substituting the standardized year 1955 to the obtained models, with the terms relating to the experimental factors removed [23].
Annual temperature and precipitation data were obtained from a meteorological station located at the Crop Research Institute in Prague-Ruzyně (Figure 1 and Figure 2). A detailed analysis of the course of the weather at the investigated site from 1954 to 2022 is described in [24].
The basic statistical values were calculated by Microsoft Excel (Microsoft Corporation, Redmund, WA, USA) and STATISTICA 14.0.0.14 software (TIBCO Software Inc., Santa Clara, CA, USA). Samples for SOC measurements from the SCR were available from 1970 and from the MCR from 1990. Therefore, trend evaluation was performed in two ways: for the whole monitoring period in the case of SCR and separately for the periods 1970–1990 and 1990–2022 to compare trends of both fields in the second time period.

3. Results and Discussion

3.1. Simple Crop Rotation

The unfertilized control of the SCR, where a rotation of two crops was operated, showed a consistent decrease in SOC content during the entire monitored period. The SOC contents dropped from 1.33% in 1955 to 1.15% in 2022. The treatment fertilized with mineral NPK had a similar tendency of decrease to SOC = 1.14%. Trends of both treatments were not significantly different (p > 0.05). On the contrary, the FYM treatment showed a constant gradual increase of SOC during the entire monitored period, resulting in SOC = 1.43% in 2022. The difference between FYM and unfertilized/NPK treatments was statistically significant (Figure 3 and Figure S1A,B; Table 2).
The trend of the NPK + FYM treatment is worth a closer look. Regarding the trend since the beginning of the trial, SOC showed stagnation (Figure 3). However, the NPK + FYM treatment showed a gradual significant increase in SOC contents to approximately 1.40–1.50% in 1990. The rate of increase was even higher than that for the FYM treatment (Figure 4 and Figure S2A,B; Table 3). Modeling SOC at the SCR also suggested that C turnover favored accumulation of SOC between 1972 and 1994, where seven out of eight simulation models predicted increasing SOC for the NPK + FYM treatment [25].
In the last two decades, a turn in the SOC content in the organically fertilized treatments has been obvious (Figure 4 and Figure S2A,B), demonstrated by a slight insignificant decrease in SOC content for the FYM treatment and a sharp (and statistically significant) decrease for the NPK + FYM treatment. These changes were also reflected in the total SOC stock in the plough layer. Within 1970–1997, the annual SOC stock increased by 97.3 kg C ha−1 and 253.1 kg C ha−1 for FYM and FYM + NPK, respectively. On the contrary, the annual increment of SOC stock for the FYM treatment reduced to 36.8 kg C ha−1 in the period 1997–2022. There was even a significant annual decrease in SOC stocks, on average by 177 kg C ha−1 for FYM + NPK. However, it must be considered that documented trends depend on the choice of the starting year, as observed, e.g., in [26].
The changes in the SOC dynamics can be linked to the gradual increase in average annual temperatures (Figure 1), which in the decade 2011–2020 was +2.3 °C compared to the decade 1970–1980. Trends demonstrated a decrease in soil organic C reserves, which were built up on organically fertilized treatments in the first cooler decades after the establishment of RFE. Contrary to our findings, Keel et al. [5] reported SOC losses at cooler sites in Swiss long-term experiments, with mean annual temperatures below 9 °C. However, they found that changes in air temperature did not prove to be a significant factor in SOC losses. Ross et al. [27] found the opposite trend of SOC content in a 12-year field experiment with rye monoculture. Although the mean temperature between September and July increased significantly in the second half of the experiment, SOC content evinced a sharp increase in the case of FYM + NPK and FYM + PK fertilization. However, control and NPK fertilization showed a slight increase in SOC content compared to the first six years, when the trend of SOC content was stagnant or decreasing. The authors also attributed the increasing SOC trend in the second half of the experiment to the change in rye cultivar.
The combination of high temperatures with higher precipitation could negatively affect SOC content [28]. Simulation models also showed that increasing temperatures negatively affect C storage in the soil. For example, a regional model simulating the future SOC dynamics in cropland and grassland soils of Bavaria in the 21st century showed a significant SOC decrease of 11–16% at an expected mean temperature increase of 3.3 °C, assuming unchanged C inputs [1]. Results indicated that C inputs must increase by 29% to maintain current SOC stocks in agricultural soils. On the other hand, the review simulating the likely changes in SOC with warming concluded that warming would have the effect of reducing SOC by stimulating decomposition rates [29]. In contrast, the effect of increasing CO2 may simultaneously imply an increase in SOC through higher net primary production. However, any changes in SOC are also likely to be very slow.

3.2. Multi-Crop Rotation

Compared to the calculated SOC = 1.29% in 1955, no significant decrease in SOC was recorded on any of the treatments of multi-crop rotation, including forage crops (Figure 5; Table 4). Unlike SCR, even for the control treatment the SOC contents showed stagnation and reached 1.28% on average for the last nine-year rotation (Figure S3A). SOC contents of all fertilized treatments were higher in the last crop rotation than in 1955 (1.35% for NPK, 1.42% for FYM, and 1.54% for FYM + NPK). Annual increases in SOC stock ranged from 31 kg C ha−1 for NPK to 80 kg C ha−1 for FYM + NPK. SOC contents for treatments with manure application were significantly higher compared to those without manure application (Figure S3B–D). It was demonstrated that the long-term manure application significantly improved SOC compared to the unfertilized control and mineral N application, despite the increase in temperature [30]. Application of organic fertilizers was found to achieve long-term stable yields while maintaining soil at optimal quality, including higher quality of humus compared to mineral-only fertilization [21].
While SOC content was more-or-less stagnant under the NPK treatment in the period 1990–2022, a slight insignificant increase in SOC in control and FYM treatments was recorded (Figure S3B–D). The increase was significant for the FYM + NPK treatment. Trends of SOC contents appeared consistent throughout the monitoring period. Trend modeling showed periodic interannual changes according to the crop sequence, with SOC minima in the year of spring barley under sown by alfalfa and two maxima in the second year of alfalfa and the year of sugar beet cultivation [23]. Balík et al. [31] studied SOC stock in long-term field experiments (22–50 years in duration) on a Cambisol at four sites in the Czech Republic. Seven crops (clover, winter wheat, early potato, winter wheat, spring barley, potato, and spring barley with inter-seeded clover) were successively rotated in the sequence and organic and mineral fertilization was applied. The application of balanced mineral fertilizer in conjunction with farmyard manure resulted in an increased soil C sequestration, specifically by 22.9% in the FYM treatment and 45.6% in the FYM + NPK treatment.

3.3. Effect of Crop Rotation Complexity

Data from 1989 to 2022 were used to compare SOC contents at fields differing in crop rotations (Figure 5 and Figure S3A–D). Intensive soil cultivation and unbalanced crop rotation on the SCR negatively affected SOC content compared to MCR. Significant differences between crop rotations were evident for all treatments, except for FYM. While SOC contents stagnated or slightly increased over time on the MCR in the case of the control, on NPK and FYM + NPK treatments, there was a significant decrease in SOC on the SCR. According to the result, the positive influence of the multi-crop rotation was evident for all treatments. Multi-crop rotation appears to be sustainable long term for stabilizing the level of soil organic C in a wide scale of fertilization scenarios thanks to the varied composition of cultivated crops, including forage crops. However, this conclusion might not hold for all combinations of soil, climate, and agronomy conditions. A positive effect of the diversified crop rotation with six different crops (including cover crops) on SOC stock, compared to a two-crop rotation with sugar beet and winter wheat, was not confirmed [32]. In contrast to our experiment, the remaining post-harvest sugar beet and wheat residues on the field played a positive role in SOC dynamics. Buysse et al. [33] did not attach as much importance to crop residues for C storage as to manure. While FYM caused significant SOC increases (10 g C year−1 over 50 years), treatment with residue restitution did not influence a significant SOC trend over the 50 years of the experiment. The authors justified this by noting the better C stabilization in manure than in crop residues, which is in agreement with the study from another Czech long-term field trial [34]. On the other hand, Koga et al. [35] concluded that not only manure application but also continuous C input to the soil through crop residue return is an essential practice for increasing C sequestration on an Andisol in northern Japan. Prudil et al. [36] simulated changes in SOC in the monoculture of spring barley and the Norfolk crop rotation during 1972–2100 using the RothC-263.3 model. Results showed that SOC stocks of Gleyic Fluvisol were mainly influenced by plant residue inputs and exogenous organic materials’ application.
The negative impact of crop rotation on SCR was partly compensated by the farmyard manure application without mineral fertilizers. The expected positive effect of manure application on the soil C content was thus confirmed in both fields, which is in accordance with our previous results [17] or similar studies by other authors [16]. Similarly, the authors of [37] showed the greatest potential of nine-year crop rotation to increase the stable C content in the soil. Cultivation of crops with high C/N residues and the re-introduction of leguminous meadows can both represent successful agronomic management to maintain a good fertility level and to lower the carbon dioxide concentration in the atmosphere.

3.4. Carbon Sequestration

To demonstrate the impact of changes in SOC dynamics on the SOC stock balance in the plough layer, we calculated 10-year averages and rates of C sequestration (Table 5 and Table 6). SOC stock in the plough layer was gradually depleted from the unfertilized plots on the SCR from −2.1 to −5.1 t C ha−1. A negative balance was also observed in treatments with NPK application, where the C sequestration was negative, from −1.6 to −3.7 t C ha−1. On the other hand, treatment with farmyard manure application showed a positive C balance, despite that the sequestration rate was negative in the last monitored period (as well as for other SCR treatments; Table 6). Organic amendments, particularly FYM application, played a pivotal role in promoting soil organic carbon (SOC) gain, as was shown in a synthesis study of German long-term field experiments [38]. These findings were also confirmed by research from Swiss long-term experiments [5], which indicated that fertilization with manure combined with higher doses of NPK fertilization had a positive effect on reducing SOC losses. Additionally, Ross et al. [27] observed the highest C sequestration rates of up to 0.5 t h−1 year−1 with a combination of mineral and FYM fertilization in a long-term field experiment with a winter rye monoculture.
On the contrary, in the present study, C sequestration decreased from 2.1 to 0.9 t C ha−1 in the case of NPK together with manure. This may be related to a higher decomposition of organic matter because of additional mineral N fertilization in the warmer period of 2000–2021. However, it should be considered that the SOC content in 1955 was used as a reference value.
Sequestration trends in treatments of MCR differed from those of SCR (Table 5). C sequestration on the unfertilized control was negative; however, it seems that over the course of the experiment, it tended toward neutral values (shifted from −1.8 to −0.3 t C ha−1). A positive C balance was observed in fertilized treatments; however, significant differences existed between these treatments. While mineral NPK fertilization resulted in only a slight increase in C sequestration, from 1.0 to 1.5 t C ha−1 over three decades, both FYM and FYM + NPK applications increased C sequestration more intensively. Even in the case of manure-fertilized variants, it appears that the C sequestration trend has halted and stabilized in the last decade. In summary, C sequestration was significantly higher in crop rotations with a more diverse crop composition, with organically fertilized treatments increasing SOC stocks by an additional 88%.
The average SOC stock in Europe varies from 40 to 600 t ha−1, depending on the soil type, texture, and land use [39]. However, in intensively managed soils, SOC stock tends to be in the tens of t/ha. Specifically, in Switzerland, SOC stock in arable soil exceeds 50 t ha−1 [40], in Belgium it is approximately 55 t ha−1 [41], and in Germany it is around 60 t ha−1 [39]. SOC stock is indeed highly influenced by management practices, which can result in significant differences, sometimes even doubling the SOC stock under different management regimes. For example, Prudil et al. [36] demonstrated that C sequestration for the monoculture of spring barley ranged from 40 to 66 t ha−1. In contrast, the Norfolk crop rotation, which includes cereals, root crops, and forage crops, exhibited higher C sequestration levels, averaging approximately 70 to 100 t ha−1. Therefore, even continuous changes on the order of a few t C ha−1 per decade are not insignificant or negligible.
These results correspond to previously published data showing that diversified crop rotations contribute to higher C contents in the soil and thus to higher C sequestration. McDaniel et al. [42] found that adding one or more crops in rotation to a monoculture increased total soil C by 3.6% and total N by 5.3%. Grunwald et al. [32] documented significantly higher SOC stocks at a 0–20 cm soil depth in the sugar beet–winter wheat–winter wheat crop rotation compared to the sugar beet–winter wheat–silage maize one. Differences in SOC stocks were likely due to the different amounts and possibly the quality of crop residue C input. Management of post-harvest residues determines SOC stocks in the soil. Incorporation of aboveground sugar beet residues by tillage resulted in a SOC stock increase of 1.9 t C ha−1 for the regular amounts of residues compared to the removed residue treatment, while stocks increased a further 0.5 t C ha−1 for the doubled residue treatment compared to the regular residue amount [33]. In general, crop rotations providing more soil organic matter, e.g., through green manure or grass-clover cultivation, has many beneficial effects on soil properties and productivity, including C accumulation [43].

4. Conclusions

Evaluation of SOC dynamics in topsoil of the oldest Czech long-term field experiment identified multi-crop rotation with fodder as the key management strategy for increasing or at least maintaining SOC stocks long term. On the contrary, a simple crop rotation with only two crops appeared more sensitive to rising temperatures and showed higher SOC losses. These losses can be partially mitigated by FYM fertilization. Our results showed that a combination of appropriate management strategies, i.e., diversified crop rotation and FYM fertilization, can attenuate the negative impacts of environmental conditions on SOC stock or amplify the positive effects. These results are consistent with findings from other European long-term field experiments and need to be implemented into Good Agricultural Practices policy to prevent significant losses of SOC stocks in European agricultural soils.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agriculture14060818/s1, Figure S1 (A). Dynamics of soil organic C content (SOC) in topsoil of SCR for the period of 1970–2022 for the control and NPK. Average values of SOC ± 95% confidence bands; (B). Dynamics of soil organic C content (SOC) in topsoil of SCR for the period of 1970–2022 for FYM and FYM + NPK. Average values of SOC ± 95% confidence bands; Figure S2 (A). Dynamics of soil organic C (SOC) content in topsoil of SCR, treatments FYM and FYM + NPK for the periods of 1970–1997. Average values of SOC ± 95% confidence bands; (B). Dynamics of soil organic C (SOC) content in topsoil of SCR, treatments FYM and FYM + NPK for the periods of 1997–2022. Average values of SOC ± 95% confidence bands; Figure S3 (A). Dynamics of soil organic C content (SOC) in the topsoil of SCR and MCR for the control in the period of 1990–2022. Average values of SOC ± 95% confidence bands; Figure S3 (B). Dynamics of soil organic C content (SOC) in the topsoil of SCR and MCR for NPK in the period of 1990–2022. Average values of SOC ± 95% confidence bands; Figure S3C. Dynamics of soil organic C content (SOC) in the topsoil of SCR and MCR for FYM in the period of 1990–2022. Average values of SOC ± 95% confidence bands; Figure S3D. Dynamics of soil organic C content (SOC) in the topsoil of SCR and MCR for FYM + NPK in the period of 1990–2022. Average values of SOC ± 95% confidence bands.

Author Contributions

Conceptualization, E.K. and T.Š.; methodology, E.K. and T.Š.; validation, T.Š. and M.M. (Mikuláš Madaras); formal analysis, M.M. (Markéta Mayerová) and T.Š.; investigation, T.Š.; resources, T.Š. and E.K.; data curation, T.Š. and M.M. (Markéta Mayerová); writing—original draft preparation, T.Š., M.M. (Markéta Mayerová) and M.M. (Mikuláš Madaras); writing—review and editing, M.M. (Markéta Mayerová), M.M. (Mikuláš Madaras) and T.Š.; supervision, M.M. (Mikuláš Madaras); project administration, E.K. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Ministry of Agriculture of the Czech Republic, grant numbers QK21020155 and RO0423.

Institutional Review Board Statement

Not applicable.

Data Availability Statement

Some data are available upon reasonable request from the corresponding author.

Acknowledgments

We thank Michaela Friedlová for the precise analyses of organic carbon in soil samples.

Conflicts of Interest

The authors declare no conflicts of interest.

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Agriculture 14 00818 g001
Figure 1. The course of temperatures at the Prague-Ruzyně site for the period 1953–2022. Average values for individual years and moving average.
Figure 1. The course of temperatures at the Prague-Ruzyně site for the period 1953–2022. Average values for individual years and moving average.
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Figure 2. The course of precipitation at the Prague-Ruzyně site for the period 1953–2022. Average values for individual years and moving average.
Figure 2. The course of precipitation at the Prague-Ruzyně site for the period 1953–2022. Average values for individual years and moving average.
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Figure 3. Dynamics of soil organic C (SOC) content in topsoil of SCR for the period of 1970–2022.
Figure 3. Dynamics of soil organic C (SOC) content in topsoil of SCR for the period of 1970–2022.
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Figure 4. Dynamics of soil organic C (SOC) content in topsoil of SCR, and treatments FYM and FYM+NPK for the periods of 1970–1997 and 1997–2022.
Figure 4. Dynamics of soil organic C (SOC) content in topsoil of SCR, and treatments FYM and FYM+NPK for the periods of 1970–1997 and 1997–2022.
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Figure 5. Dynamics of soil organic C (SOC) content in the topsoil of MCR for the period of 1990–2022.
Figure 5. Dynamics of soil organic C (SOC) content in the topsoil of MCR for the period of 1990–2022.
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Table 1. Fertilization in the long-term field experiments (mean application rates for crop rotation).
Table 1. Fertilization in the long-term field experiments (mean application rates for crop rotation).
Block/Crop RotationNPKFarmyard Manure
kg ha−1 year−1t ha−1 year−1
Field B—simple crop rotation (SCR)100267510.5
Field IV—multi-crop rotation (MCR)63241096.5
Table 2. Summary of statistical analysis of soil organic C (SOC) content dynamics in topsoil of SCR for the period of 1970–2022.
Table 2. Summary of statistical analysis of soil organic C (SOC) content dynamics in topsoil of SCR for the period of 1970–2022.
Treatmentr2rmp-ValueCI − 95%CI + 95%
Control0.314−0.561 **−0.0030.0011.151.207
NPK0.108−0.329 *−0.0020.0321.2151.27
FYM0.01160.341 *0.0020.0271.3841.451
FYM + NPK0.001−0.021 ns−0.0000.8931.3451.421
r2 = Coefficient of determination; r = Pearson’s correlation coefficient; CI = confidence intervals; m = regression slope from regression equation; * p < 0.05, ** p < 0.01, ns = not significant.
Table 3. Summary of statistical analysis of soil organic C (SOC) content dynamics in topsoil of SCR for the periods of 1970–1997 (I.) and 1997–2022 (II.).
Table 3. Summary of statistical analysis of soil organic C (SOC) content dynamics in topsoil of SCR for the periods of 1970–1997 (I.) and 1997–2022 (II.).
StatisticControlNPKFYMFYM + NPK
I.II.I.II.I.II.I.II.
r20.1080.1520.0040.4710.0690.0020.2310.236
r−0.328 ns−0.39 *−0.06 ns−0.686 **0.262 ns−0.043 ns0.481 *−0.486 *
m−0.003−0.004−0.001−0.0060.0032−0.0010.008−0.006
p-value0.1840.0490.8130.0000.2930.840.0430.014
CI − 95%1.1831.1141.2091.2011.3191.4071.3191.339
CI + 95%1.2741.1741.3141.2611.4291.4871.4631.426
r2 = Coefficient of determination; r = Pearson’s correlation coefficient; CI = confidence intervals; m = regression slope from regression equation; * p < 0.05, ** p < 0.01, ns = not significant.
Table 4. Summary of statistical analysis of soil organic C (SOC) content dynamics in topsoil of MCR for the period of 1990–2022.
Table 4. Summary of statistical analysis of soil organic C (SOC) content dynamics in topsoil of MCR for the period of 1990–2022.
Treatmentr2rmp-ValueCI − 95%CI + 95%
Control0.0770.277 ns0.0020.1311.2131.271
NPK0.0220.147 ns0.0010.4311.2991.348
FYM0.0350.187 ns0.0020.3151.3641.424
FYM + NPK0.110.332 ns0.0030.0681.4731.526
r2 = Coefficient of determination; r = Pearson’s correlation coefficient; CI = confidence intervals; m = regression slope from regression equation; ns = not significant.
Table 5. Carbon sequestration for individual treatments of the experiment for the period 1971–2020.
Table 5. Carbon sequestration for individual treatments of the experiment for the period 1971–2020.
Crop RotationPeriodC Sequestration Since 1955
(t C ha−1, Average for the Decade)
ControlNPKFYMNPK + FYM
SCR1971–1980−2.10−1.560.792.07
1991–2000−4.37−1.573.144.71
2011–2020−5.11−3.704.860.92
MCR1991–2000−1.821.012.845.58
2011–2020−0.331.554.677.55
Table 6. Carbon sequestration rates over decades, from 1971 to 2020.
Table 6. Carbon sequestration rates over decades, from 1971 to 2020.
Crop RotationC Sequestration Rate
(t C ha−1 Year−1)
1971–19801991–20002011–2020
mr2mr2mr2
SCR
Control0.0790.010−0.0140.001−0.2570.289
NPK−0.2770.0460.3710.341−0.1410.320
FYM−0.0860.0060.4650.161−0.2610.161
FYM + NPK0.6110.3170.2440.054−0.1910.174
MCR
Control 0.2490.117−0.0680.004
NPK 0.4980.3760.1570.048
FYM 0.1790.0610.0250.001
FYM + NPK 0.4160.290−0.0320.002
m = Regression slope from regression equation; r2 = coefficient of determination.
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Šimon, T.; Madaras, M.; Mayerová, M.; Kunzová, E. Soil Organic Carbon Dynamics in the Long-Term Field Experiments with Contrasting Crop Rotations. Agriculture 2024, 14, 818. https://doi.org/10.3390/agriculture14060818

AMA Style

Šimon T, Madaras M, Mayerová M, Kunzová E. Soil Organic Carbon Dynamics in the Long-Term Field Experiments with Contrasting Crop Rotations. Agriculture. 2024; 14(6):818. https://doi.org/10.3390/agriculture14060818

Chicago/Turabian Style

Šimon, Tomáš, Mikuláš Madaras, Markéta Mayerová, and Eva Kunzová. 2024. "Soil Organic Carbon Dynamics in the Long-Term Field Experiments with Contrasting Crop Rotations" Agriculture 14, no. 6: 818. https://doi.org/10.3390/agriculture14060818

APA Style

Šimon, T., Madaras, M., Mayerová, M., & Kunzová, E. (2024). Soil Organic Carbon Dynamics in the Long-Term Field Experiments with Contrasting Crop Rotations. Agriculture, 14(6), 818. https://doi.org/10.3390/agriculture14060818

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