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Article

Compressibility of a Cambisol Submitted to Periods of Rotational Grazing and Strategies to Avoid Additional Soil Compaction

by
Luis Eduardo Akiyoshi Sanches Suzuki
1,*,
Darcy Bitencourt Junior
2,
Eloy Antonio Pauletto
3,
Ezequiel Cesar Carvalho Miola
3,
Pablo Rostirolla
1 and
Gilberto Strieder
1
1
Center of Technological Development, Federal University of Pelotas, Pelotas 96010-610, RS, Brazil
2
Instituto Federal de Educação, Ciência e Tecnologia Sul-Rio-Grandense (IFSul), Campus Pelotas—Visconde da Graça, Pelotas 96060-290, RS, Brazil
3
Soils Department, Federal University of Pelotas, Capão do Leão 96050-500, RS, Brazil
*
Author to whom correspondence should be addressed.
Conservation 2023, 3(3), 334-345; https://doi.org/10.3390/conservation3030023
Submission received: 24 April 2023 / Revised: 15 June 2023 / Accepted: 20 June 2023 / Published: 26 June 2023
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Abstract

:
Soil compaction is one of the main causes of soil degradation, and some parameters have been used to characterize it, like those related to compressibility and the degree of compactness. To evaluate the rotational grazing time during winter and the presence and absence of grazing, on the compressibility and degree of compactness of a Cambisol, an experiment was installed and consisted of corn planting for silage, a fallow and pasture planting period, with two treatments evaluating the amount of rotational grazing (two and three times in a period of, respectively, 2 and 3 months), subdivided into the presence and absence of dairy cattle grazing. The mean bulk density value of 1.47 Mg/m3 separates the occurrence (plastic deformation) or not (elastic deformation) of additional soil compaction, while the traffic of machinery and animal trampling should occur with soil moisture lower than 0.23 kg/kg, when the soil has a larger load-bearing capacity. For the conservation of soil structure, our study recommends the permanence of cattle in the plots for 30 to 40 min/day and an exit when the pasture height is 0.07 to 0.10 m, with two or three grazing in a period of, respectively, 2 and 3 months.

1. Introduction

From 1985 to 2021, there was a loss of native vegetation in all Brazilian biomes (Amazon 11.5%, Caatinga 10.1%, Cerrado 20.9%, Atlantic Forest 5.9%, Pampa 29.5%, Pantanal 12.1%) and a significative replacement of native vegetation for planted pasture [1], representing areas with livestock, including 46 Mha of natural fields and 45 Mha of agriculture and livestock mosaics [2]. On the other hand, despite the advance of livestock in the Brazilian Biomes in the last few years, data from 2020 indicated 47.7% of the pastures as not degraded, while 38% with an intermediary level of degradation and 14.3% severely degraded [2]. These data show the urgency to stop the deforestation of biomes and recover the degraded pastures for food production and maintain and conserve the soil and pastures not degraded through management strategies of soil, pastures and animals.
Soil compaction is a great agent of soil degradation, which can negatively influence soil properties, such as bulk density, porosity, resistance of soil to penetration, hydraulic conductivity [3,4,5], nutrient uptake by plants, such as phosphorus and potassium, which are absorbed by plants through a diffusion process [6], restrict root growth [3,7,8] and reduce crop yield [9], as well as the impact on the environment through soil erosion [10] and environment pollution [11], in addition to economic losses [11,12]. For pasture lands, animals trampling can negatively affect the soil structure [4,13,14,15,16,17], especially on intense and more frequently grazed pastures [18], making it necessary to define periods of grazing exclusion [19], aiming for soil conservation, preventing its degradation and making possible pasture growth and development. Monitoring the soil physical properties (porosity, bulk density and air permeability) verified that periods of grazing exclusion alleviate compaction in a clayey Oxisol managed under different intensities of dairy cattle grazing [20], while soil compaction increased with an increment in grazing pressure, and erosion rates varied with grazing management, with soil erosion and sediment delivery to waterways being reduced with fenced riparian buffers associated with rotational grazing management [21]. Determining the grazing exclusion period and knowledge of the soil physical properties in the context of soil–plant–animal systems are important in maintaining the sustainable pastures [19].
In that regard, to avoid additional soil compaction, it is important to know the levels of pressure that the soil has suffered in the past and/or the soil moisture at the time of machinery traffic or animal trampling. Therefore, the application of loads lower than the precompression stress causes elastic deformations (recoverable) in the soil, while the application of greater loads causes plastic deformations, which are not recoverable [22] and can negatively modify soil structure [23,24]. Thus, knowledge on the change from elastic to plastic properties and alterations in the function of the soil is important to improve or maintain soil functions, such as air and water fluxes, enabling root penetration in the soil, filtering and buffering [25].
From the knowledge of the precompression stress and compression index, and their existing relationship with moisture and bulk density [23,24,26,27,28,29,30,31], the soil and the traffic of machinery and animals trampling can be managed in order to avoid additional compaction. Soil bulk density is a good indicator of compaction [8], and some authors have verified a relationship between precompression stress and/or compression index with bulk density [23,24,26,29,32,33].
In addition to bulk density, the degree of compactness has been efficient in characterizing soil compaction and the response of annual crops in different soils [4,34,35,36,37,38], but in pasture lands, few studies have been carried out with the degree of compactness [4,39], reinforcing the need to study this parameter for this land use also. Despite the bulk density being a good indicator of soil compaction, it is dependent on the soil texture, making comparisons between different soils difficult; on the other hand, the degree of compactness is indirectly dependent on the texture [4,35,37,38], which makes it possible to compare the state of compaction between different soils.
Despite studies solving soil compaction through tillage, such as chiseling, it is a costly operation, and the compaction returns after some period according to soil management [9,40]. In addition, the soil tillage exposes the topsoil to erosion [27]. Therefore, the best strategy is to prevent additional soil compaction through knowledge of precompression stress and monitoring soil moisture to define the most adequate moment for traffic of machinery and animal trampling. Rotational grazing is one more strategy that joins to those to avoid additional compaction, but further studies are necessary to define the most suitable time of grazing to maintain adequate soil structure. Dong et al. [41] verified that rotational grazing is a better way to maintain adequate soil functions and the income of local farmers.
Strategies for the sustainable management of soil, pasture and animals are necessary for soil and environmental conservation, as well as the profits of farmers, setting them in farms and food production. Parente and Maia [19], in a review of Brazilian Semiarid, cited the necessity to understand how the soil physical properties respond to intense grazing and, consequently, pastures, to support decision making.
Given this context, the present study aimed to compare the rotational grazing time during winter and the presence and absence of grazing, on the compressibility and degree of compactness of a Cambisol, and propose strategies to avoid additional soil compaction, seeking the adequate management and conservation of soil and pasture lands. Our hypotheses are: (1) rotational grazing change the compressibility and degree of compactness of the soil compared to no grazing; (2) the presence or absence of grazing and the amount of grazing differently influence the compressive parameters of soil; (3) precompression stress presents a relationship with soil moisture and bulk density, being possible to use that relationship to avoid additional soil compaction.

2. Materials and Methods

The experimental area is located in the municipality of Rio do Sul, Santa Catarina State, Brazil. The altitude of the region is approximately 700 m, and the predominant climate in the region is subtropical type Cfb (humid mesothermal with hot summer). The annual mean temperature, relative humidity and precipitation are, respectively, 18 to 19 °C, 68.7% and 1300 to 1500 mm [42]. For the study period, based on data from EPAGRI—Experimental Station of Ituporanga municipality—rainfall was 747.5 and 579 mm for the season and 748 and 527 mm for off-season, respectively, for the agricultural years 2006/2007 and 2007/2008.
The experiment was installed in a Cambissolo Háplico according to the Brazilian System of Soil Classification [43], using Inceptisol [44] and Cambisol [45], with around 26% clay, 50% silt and 26% sand, silt loam textural class, organized in a randomized block design, with three blocks. Previously, for the installment of the experiment, the soil presented the following chemical characteristics: pH = 5.6; phosphorus = 15.3 mg/dm3; potassium = 47.2 mg/dm3; organic matter = 3.0%; aluminum = 0.12 cmolc/dm3; calcium = 4.14 cmolc/dm3; magnesium = 2.8 cmolc/dm3.
The research started in 2005 with the planting of pasture to obtain biomass for the corn crop. Prior to the implementation of the experiment, the area was under no tillage for three years. The experiment consisted of planting corn for silage, a fallow period and planting pasture, with two treatments evaluating the amount of rotational grazing (2 and 3 times in a period of, respectively, 2 and 3 months) (Figure 1), subdivided into presence of grazing by dairy cattle and absence (mechanical cutting). More information about the experiment can be obtained in Bitencourt Junior [46].
The cattle load used in the 2006 season/2007 off-season was 7200 kg/300 m2, and in the 2007 season/2008 off-season, it was 7400 kg/300 m2; permanence of cattle in the plots for 30 to 40 min/day, for three days, and the minimum availability of pasture for entrance were 1500 kg of dry biomass/ha, and for exit, the residual pasture height was 0.07 to 0.10 m. In the period of 2 months of grazing, the animals entered the area twice, while in the period of 3 months, they entered the area three times. The mean period between grazing/cutting in the plots was 29 days, varying between 22 and 36 days.
In one of the treatments, corn was sown in October and November and harvested in March, the plots remaining in fallow, and then planting pasture, remaining in the plots for approximately two months. In the other treatment, the off-season corn was sown in January and February, being harvested in May and until the pasture was sown, which remains in the area for approximately three months; the area remains fallow (Figure 1).
Corn sowing (hybrid corn AS32 Agroeste) was carried out in no tillage with a Valmet 785 tractor and four-line seeder, on straw desiccated with glyphosate (2.0 L/ha), and the silage was harvested with a forage harvester coupled on a Massey Ferguson 292 traced tractor and a trailer that received the silage. At the time of desiccation, the dry biomass was 2.28 and 3.68 and 3.7 and 4.47 t/ha, respectively, for season (22 October 2006 and 6 November 2007), with 49 and 44 days of dry biomass accumulation and off-season (5 January 2007 and 21 January 2008), with 90 and 94 days of biomass accumulation. Corn was sown with 60,000 seeds/ha and 0.80 m spacing between rows. The cut for silage was carried out with the grain at the hard-mealy stage.
The implantation of the winter pasture was carried out with minimum tillage using disc harrowing, with broadcast sowing on 29 May 2006 and 14 June 2007, with a mixture of black oat (Avena strigosa Scherb.) (50 kg/ha), ryegrass (Lolium multiflorum Lam.) (15 kg/ha) and vesicular clover (Trifolium vesiculosum Savi) (12.5 kg/ha), the latter only in the first year. The time to start using the pasture was 45 and 65 days (from implantation to the first grazing), respectively, for 2006 and 2007.
The soil sampling with preserved structure was carried out from October to November/2007 for 2 months of grazing and January/2008 for 3 months of grazing, in metallic cylinders with 4.85 cm of diameter and 3.00 cm of height. Six samples per plot and soil layer were collected from 0.00 to 0.05; 0.05 to 0.10; 0.10 to 0.15; and 0.15 to 0.20 m, totaling 18 samples per treatment and depth.
The soil samples were saturated by capillarity to determine the total porosity and submitted to a tension of 10 kPa in Richards pressure chambers to be submitted to the uniaxial compression test, with application of successive and static loads of 25; 50; 100; 200; 400; 800; and 1600 kPa, in the consolidometer CNTA-IHM/BR-001/07 model to determine the precompression stress and the compression index, the bulk density corresponding to the precompression stress and the deformation of the soil samples after the compression test. After the compression test, the samples were placed in an oven at 105 °C for drying and calculation of moisture and bulk density.
The degree of compactness (DC, %) was calculated using the equation:
DC = (BD/BDref) × 100
where: BD is the current soil bulk density and BDref is the reference bulk density obtained after applying a load of 1600 kPa in the uniaxial compression test [38].
Statistical analysis was performed using analysis of variance considering the amount of rotational grazing (two and three times, respectively, in 2 and 3 months), grazing (with or without grazing) and soil layer (0.00 to 0.05; 0.05 to 0.10; 0.10 to 0.15; 0.15 to 0.20 m). When the analysis of variance was significative, the comparison of means was realized through Tukey’s test at 5% significance. Pearson’s correlation analysis and regression analysis were also performed using the available data.
The correlation coefficients were interpreted according to the ranges proposed for Mukaka [47] and Schober et al. [48] (Table 1).

3. Results and Discussion

The mean gravimetric moisture of the samples subjected to the uniaxial compression test and balanced at 10 kPa tension was similar between treatments, although the range between the maximum and minimum value varied according to the treatments (Table 2). Based on Pimentel-Gomes and Garcia [49], the coefficient of variation was high (between 20 and 30%) and very high (larger than 30%) for two-times grazing and low (smaller than 10%) and medium (between 10 and 20%) for three-times grazing (Table 2).
Soil moisture is an important variable in the compaction process and soil compression behavior [23,24,27,28,29,30,31], because it acts as a lubricant for solid particles, belonging to the easier rearrangement of soil particles [26,50], suggesting that controlling soil moisture is a key factor in mechanized operations and animal trampling [24,51] to avoid additional compaction and maintain the soil structure.
Analysis of variance indicated a significant influence of the amount of grazing (two or three times) for degree of compactness, soil layer for precompression stress and degree of compactness and interaction between amount of grazing x presence or absence of grazing (grazing or no grazing) for compression index.
In the plots without grazing (no grazing), the permanence of the pasture for 3 months significantly decreases the susceptibility of the soil for compaction (compression index) compared to 2 months, perhaps associated with a slightly higher soil bulk density but not significant for grazing for 3 months (Table 3) because the increase in bulk density decreases the compression index [23,24,26,33,52]. No compaction was observed in time-controlled grazing compared to intensive sheep grazing, and a long rest period is the major contributor to physical and chemical recovery of the soil after each grazing operation [53]. The grazing exclusion periods alleviate compaction (measured through soil physical properties—porosity, bulk density and air permeability) in a clayey Oxisol managed under different intensities of dairy cattle grazing [20], while the increment in cattle grazing pressure increased soil compaction, and erosion rates varied with grazing management, with soil erosion and sediment delivery to waterways being reduced with fenced riparian buffers associated with rotational grazing management [21].
The current bulk density is equal or close to that corresponding to the precompression stress (BDPPC) (Table 3), indicating that if the soil suffers loads larger than those already applied, the soil bulk density will increase and, consequently, there will be a decrease in porosity, water and air flow [23,24], with possible damage to the environment due to soil erosion and its consequences.
The precompression stress and the degree of compactness were lower in the topsoil and statistically differed from the deeper soil layers (Table 4). On the other hand, the highest values of the degree of compactness were in the surface layer (0–0.10 m) of a Typic Paleudalf with pasture for five years and cattle trampling [4]. The lower precompression stress and degree of compactness in the topsoil may be associated with the large volume of corn and pasture roots in the surface soil layer, the input of straw and organic matter, In addition, the minimum tillage was with light harrowing to installation of pasture in the winter [54]. In addition, soil compressibility, which may be considered the resistance of the soil to compact when subjected to load, depends on soil resistance, particle size distribution, clay-mineral type, content and type of organic materials, root distribution, soil bulk density, pore size distribution and continuity in the soil and in simple aggregates and soil moisture and/or water potential [55].
In a Vertisol, grazing with a high load (40 animals of approximately 385 kg per hectare) did not cause an increase in bulk density or significant changes in the precompression stress and compression index compared to the area without grazing, a fact attributed to the greater amount of organic material on the soil surface, leading to a high load-bearing capacity, low susceptibility to compaction and high soil elasticity [56]. On the other hand, the excessive stocking rates of cows caused a depletion in physical properties in a typical Red distroferric Latossol, reducing the volume of macropores and increasing bulk density [57].
The mean values of precompression stress range between 193.48 and 240 kPa (Table 4), values extremely high according to classification proposed by Horn and Fleige [58]. The authors classified precompression stress values as very low (<30 kPa), low (30–60 kPa), medium (60–90 kPa), high (90–120 kPa), very high (120–150 kPa) and extremely high (>150 kPa), using, for this classification, pF values of 1.8 and 2.5 (respectively, for soil when macropores are drained by water and soil at field capacity), bulk density and shear strength parameters. On the other hand, precompression stress was low for different soil land uses (pasture, eucalyptus and anthropized forest) in a Typic Paleudalf, ranging from 31.24 to 50.92 kPa [24], while values of 268 and 246 kPa, respectively, for irrigated and non-irrigated intensive rotational cattle grazing were found in a Hapludalf, with soil samples equilibrated at 10 kPa tension [59]. Stresses applied on the ground by a horse’s hoof can exceed 300 kPa [60].
The degree of compactness in the 3-times grazed plots is higher and significantly different from the 2-times grazed plots (Table 4), but the values are adequate considering that the highest soybean yield was obtained with an intermediate degree of compactness of 82% for Alfisols and Ultisol and 85% for Oxisols [38]. According to the authors, a low degree of compactness hinders soil–root contact and water retention in the soil, while a high degree of compactness decreases soil aeration and increases its resistance to penetration, negatively affecting root growth and development. In a Typic Paleudalf under grazed pasture, the mean value of degree of compactness was 80.4% to the 0–1.00 m depth, with the larger values in the topsoil (0–0.10 m) and decreasing with depth [4].
Increasing total porosity (r = 0.20 **) and decreasing bulk density (r = −0.19 *) increase soil susceptibility to compaction, although with a weak correlation coefficient (Table 5). As a consequence, the greater the soil deformation in the uniaxial compression test, the greater the susceptibility of the soil to compaction (r = 0.56 **), which means that high compaction is related to a lower susceptibility for compaction, resulting in less deformation when the soil is subjected to loads greater than the precompression stress [26]. The correlation coefficient ranged from weak to very strong, predominating moderate and strong (Table 5). Even for a weak correlation coefficient, it was significant at 1 and 5%.
The increase in soil bulk density (r = 0.50 **) and the decrease in total porosity (r = −0.51 **) increase the load-bearing capacity of the soil (precompression stress) and decrease soil deformation in the uniaxial compression test (r = −0.66 **) (Table 5), probably because the soil is more compact and less porous, although it does not indicate that this compaction is restrictive to plant growth, which also decreases its susceptibility to compaction. The increase in soil moisture decreases the load-bearing capacity (r = −0.27 **), probably because water lubricates soil particles, facilitating the displacement and rearrangement of particles in the void spaces of the soil [50].
In an Oxisol with a clayey texture, the precompression stress increases as the soil is dry [61]. Soil deformation when subjected to loads occurs when the particles are able to disperse and move towards each other, having their displacement limited by friction and connections between particles; therefore, the more compacted the soil, the greater the forces of friction, which are responsible for soil resistance [62].
Increasing the degree of compactness decreases the total porosity (r = −0.77 **) and its susceptibility to compaction (r = −0.56 **) and increases the bulk density (r = 0.74 **) and precompression stress (r = 0.66 **) (Table 5).
Similarly, significant (p < 0.01) and positive correlations between soil deformation and compression index, significant (p < 0.01) and negative correlation between soil bulk density and compression index and between deformation and precompression stress were found by other authors [26], although they did not find a significant correlation between bulk density and precompression stress. On the other hand, other authors also observed correlation between the bulk density and precompression stress and no correlation between the bulk density and compression index [32].
Considering these significant relationships, soil compaction and load-bearing capacity can be monitored based on bulk density, as well as defining the most suitable moisture range for machinery traffic and cattle trampling in the area without causing additional compaction. These are strategies for soil and environmental conservation, avoiding their degradation. Based on the regression between soil bulk density and precompression stress (Figure 2), the mean bulk density value of treatments = 1.47 Mg/m3 (2-times grazing = 1.46 Mg/m3, and 3-times grazing = 1.48 Mg/m3, Table 2) separates the occurrence (plastic deformation) or not (elastic deformation) of additional compaction in the soil; that is, bulk densities higher than this value indicate additional compaction and an alteration in the soil structure, with an increase in bulk density and a decrease in porosity and hydraulic conductivity.
To avoid additional compaction under these experimental conditions, the machinery traffic and cattle trampling should occur with soil moisture lower than 0.23 kg/kg, a condition that will allow the soil to have a larger load-bearing capacity (Figure 2). On the other hand, a degree of compactness larger than 84% (corresponding to a bulk density of 1.47 Mg/m3) indicates additional soil compaction (Figure 2). Although the regression coefficients obtained for the equations are low, they are significant at 1 and 5%, and it is possible to observe the trend of the relationships presented and, even so, use them for an adequate management of the soil, pasture and animals in the areas, avoiding additional compaction and soil structure degradation.
No significative difference in our compressive results, or degree of compactness with no restrictive values for plant growth and yield, corroborates with Bitencourt Junior et al. [54] in this same experiment evaluating soil physical and hydraulic properties, making it possible to recommend rotational grazing two or three times, respectively, for periods of 2 and 3 months, with permanence of cattle in the plots for 30 to 40 min/day, for three days, and 1500 kg of dry biomass/ha as the minimum availability of pasture for entrance and residual pasture height of 0.07 to 0.10 m for exit of the cattle in the plots.
The soil–plant–animal management conducted in our study helps to conserve the soil structure and not degrade it, making adequate water and air flow in the soil and plant growth and yield possible. In addition, environmental conservation shows a sustainable management of soil, pasture and animals. A study has shown that the continuous grazing of Brachiaria decumbens associated with the pressure of the cattle trampling increased the bulk density and the resistance to penetration of an Alfisol, in an experiment conducted over 21 consecutive days, using a stocking rate of 12 AU (animal units)/ha, composed of heifers of the Girolando breed that started the grazing period with an average forage height of 0.90 m, being suspended when an average height of 0.23 m was reached [63].
Considering our results, further studies may be realized increasing the number of grazing times in a period of 2 and 3 months and the cattle load, under controlled traffic of machinery and animal trampling with soil moisture lower than 0.23 kg/kg, when the soil has a larger load-bearing capacity, to verify the moment of occurrence of additional compaction and monitor the capacity of the natural recovery of soil.

4. Conclusions

The precompression stress and the degree of compactness are lower in the surface soil layer compared to the deeper layers.
The presence or absence of grazing does not influence the compressive parameters and the degree of compactness, and the number of grazing times (two or three) does not influence the load-bearing capacity of the soil, refuting two of our hypotheses that rotational grazing change the compressibility and degree of compactness of the soil compared with no grazing, presence or absence of grazing and the amount of grazing differently influences the compressive parameters of soil.
Decreasing the total porosity and increasing the bulk density reduce soil susceptibility to compaction and increase the load-bearing capacity. Increasing the degree of compactness decreases the total porosity and its susceptibility to compaction and increases the bulk density and precompression stress. Increasing the soil moisture decreases the load-bearing capacity of the soil.
Mathematical functions were defined to monitor soil compaction and load-bearing capacity based on bulk density and the most suitable moisture range for the traffic of machinery and animals trampling into the area, without causing additional compaction, confirming our hypotheses that the precompression stress presents a relationship with soil moisture and bulk density.
Based on the presented results, for the conservation of soil structure and to avoid additional compaction, our study recommends the permanence of cattle in the plots for 30 to 40 min/day and exit when the pasture height is 0.07 to 0.10 m, with two or three grazing times in a period of, respectively, 2 and 3 months being possible in a Cambisol silt loam. Our study introduced sustainable management strategies of soil, pasture and animals, aiming at soil and environmental conservation.
For future research, we will test the increase in the number of grazing times in a period of 2 and 3 months, as well as the cattle load, controlling the traffic of machinery and animal trampling with soil moisture lower than 0.23 kg/kg, when the soil has a larger load-bearing capacity, according to our recent results.

Author Contributions

Conceptualization, D.B.J. and E.A.P.; methodology, D.B.J. and E.A.P.; formal analysis, L.E.A.S.S., D.B.J. and E.A.P.; investigation, L.E.A.S.S., D.B.J., E.A.P., E.C.C.M., P.R. and G.S.; resources, D.B.J. and E.A.P.; data curation, L.E.A.S.S. and D.B.J.; writing—original draft preparation, L.E.A.S.S. and D.B.J.; writing—review and editing, L.E.A.S.S., D.B.J., E.A.P., E.C.C.M., P.R. and G.S.; project administration, D.B.J. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Data available on request from the authors.

Acknowledgments

To IF Catarinense—Federal Institute of Education, Science and Technology Catarinense (IFC), campus Rio do Sul, for the availability of the experimental area and assistance in conducting the experiment. To the technician from the Laboratory of Soil Physics at FAEM/UFPel, Paulo Luis da Luz Antunes, for his assistance in the laboratory analyses.

Conflicts of Interest

The authors declare no conflict of interest.

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Conservation 03 00023 g001 550
Figure 1. Scheme representing the periods and crops involved in the experiment installed in a Cambisol, municipality of Rio do Sul, Santa Catarina State. * SS: soil sampling. In 2006, the experiment started in May (M), while in 2008, it ended in July (J).
Figure 1. Scheme representing the periods and crops involved in the experiment installed in a Cambisol, municipality of Rio do Sul, Santa Catarina State. * SS: soil sampling. In 2006, the experiment started in May (M), while in 2008, it ended in July (J).
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Conservation 03 00023 g002 550
Figure 2. Relationship between precompression stress (PPC) with bulk density (BD) and gravimetric moisture (GM) and bulk density with degree of compactness (DC). ** significant at 1%; * significant at 5%.
Figure 2. Relationship between precompression stress (PPC) with bulk density (BD) and gravimetric moisture (GM) and bulk density with degree of compactness (DC). ** significant at 1%; * significant at 5%.
Conservation 03 00023 g002
Table
Table 1. Interpretation of the correlation coefficients according to Mukaka [47] and Schober et al. [48].
Table 1. Interpretation of the correlation coefficients according to Mukaka [47] and Schober et al. [48].
Correlation CoefficientInterpretation
0.00–0.10Negligible correlation
0.10–0.39Weak correlation
0.40–0.69Moderate correlation
0.70–0.89Strong correlation
0.90–1.00Very strong correlation
Table
Table 2. Mean, maximum, minimum and coefficient of variation (CV) for gravimetric soil moisture (kg/kg) corresponding to 10 kPa tension (n = 288 *).
Table 2. Mean, maximum, minimum and coefficient of variation (CV) for gravimetric soil moisture (kg/kg) corresponding to 10 kPa tension (n = 288 *).
2-Times Grazing3-Times Grazing
GrazingNo GrazingGrazingNo Grazing
Mean0.230.220.250.23
Maximum0.410.300.340.26
Minimum0.110.130.190.22
CV (%)34.5328.6910.945.37
* six samples per plot, three blocks, four soil layers (0.00 to 0.05; 0.05 to 0.10; 0.10 to 0.15; and 0.15 to 0.20 m), two rotational grazing (2- and 3-times grazing) and presence and absence of grazing by dairy cattle (grazing and no grazing).
Table
Table 3. Mean values of compression index (CI), bulk density corresponding to the precompression stress (BDPPC) and bulk density (BD).
Table 3. Mean values of compression index (CI), bulk density corresponding to the precompression stress (BDPPC) and bulk density (BD).
CI BDPPC, Mg/m3 BD, Mg/m3
Number of Grazing Number of Grazing Number of Grazing
2-Times3-TimesMean2-Times3-TimesMean2-Times3-TimesMean
Grazing0.23 Aa0.23 Aa0.231.461.411.431.461.441.45
No grazing0.25 Aa0.20 Ab0.221.471.501.481.471.521.50
Mean0.240.21 1.461.45 1.461.48
Means followed by the same letter, lowercase in the row and uppercase in the column, do not statistically differ from each other by Tukey’s test at 5% significance. The absence of statistical indication corresponds to the inexistence of significant differences.
Table
Table 4. Mean values of precompression stress (PPC) and degree of compactness (DC).
Table 4. Mean values of precompression stress (PPC) and degree of compactness (DC).
PPC, kPa DC, %
Number of Grazing Number of Grazing
Layer, m2-Times3-TimesMean2-Times3-TimesMean
0.00–0.05193.48200.48196.98 B81.482.181.8 B
0.05–0.10219.22232.45225.84 A83.384.984.1 A
0.10–0.15230.67240.00235.34 A83.785.184.4 A
0.15–0.20235.82236.47236.15 A83.084.583.7 A
Mean219.80227.35 82.9 b84.2 a
Means followed by the same letter, uppercase in the column and lowercase in the line, do not statistically differ from each other by Tukey’s test at 5% significance.
Table
Table 5. Pearson’s correlation and significance between the variables related to the compressibility of a Cambisol.
Table 5. Pearson’s correlation and significance between the variables related to the compressibility of a Cambisol.
1 Variables
BDGMDefCIPPCDC
TP−0.98 **0.79 **0.77 **0.20 **−0.51 **−0.77 **
BD-−0.83 **−0.74 **−0.19 *0.50 **0.74 **
GM--0.43 **ns−0.27 **−0.43 **
Def---0.56 **−0.66 **−0.99 **
CI----ns−0.56 **
PPC-----0.66 **
1 TP, BD, GM: respectively total porosity, bulk density and gravimetric moisture at the beginning of the compressibility test; Def: soil deformation at the end of the test; CI: compressibility index; PPC: precompression stress; DC: degree of compactness. ** significant at 1%; * significant at 5%; ns: not significant. The colored background means the interpretation of the correlation coefficient according to Mukaka [47] and Schober et al. [48]: 0.10–0.39: weak correlation; 0.40–0.69: moderate correlation; 0.70–0.89: strong correlation; 0.90–1.00: very strong correlation.
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Suzuki, L.E.A.S.; Bitencourt Junior, D.; Pauletto, E.A.; Miola, E.C.C.; Rostirolla, P.; Strieder, G. Compressibility of a Cambisol Submitted to Periods of Rotational Grazing and Strategies to Avoid Additional Soil Compaction. Conservation 2023, 3, 334-345. https://doi.org/10.3390/conservation3030023

AMA Style

Suzuki LEAS, Bitencourt Junior D, Pauletto EA, Miola ECC, Rostirolla P, Strieder G. Compressibility of a Cambisol Submitted to Periods of Rotational Grazing and Strategies to Avoid Additional Soil Compaction. Conservation. 2023; 3(3):334-345. https://doi.org/10.3390/conservation3030023

Chicago/Turabian Style

Suzuki, Luis Eduardo Akiyoshi Sanches, Darcy Bitencourt Junior, Eloy Antonio Pauletto, Ezequiel Cesar Carvalho Miola, Pablo Rostirolla, and Gilberto Strieder. 2023. "Compressibility of a Cambisol Submitted to Periods of Rotational Grazing and Strategies to Avoid Additional Soil Compaction" Conservation 3, no. 3: 334-345. https://doi.org/10.3390/conservation3030023

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