Prediction of Soil Compaction using Conventional Tillage Systems under Different Operating Conditions

The field experiment was conducted in the College of Agriculture - University of Basra in Karma Ali located in the south of Basra city. The soil was of a clay-silty texture. The study aims to evaluate the negative impact of primary plowing equipment (moldboard plow, disk plow, and chisel plow) on the physical properties of the soil by studying soil compaction indicators such as soil resistance to penetration, soil bulk density, and total porosity. Three plowing depths (15, 20, and 25) cm and three forward speeds of the tractor (0.45, 0.75, and 1.05) m s-1 were used. Intelligent computing was introduced to predict results and simulate soil compaction through the use of Design Expert software. The results showed that there is an effect of all studied factors on the variables of soil physical properties. The effect on the soil penetration resistance characteristic of the type of plow was greater than the depth, and the depth was greater than the forward speed, as the soil penetration resistance was (4.53, 3.84, and 3.23) MPa for the moldboard plow, disc plow, and chisel plow, respectively. As for the effect of increasing the depth, it was 27%, while the effect of increasing the forward speed was 24%. As for the bulk density of the soil, the effect of the type of plow was also greater than the effect of the increase in depth, and the increase in depth was more effective than the increase in the forward speed, as the bulk density was (1.68, 1.52, and 1.48) g.cm-3 for the moldboard, disc, and chisel, respectively. As for the effect of depth, it reached 7%, while the effect of speed reached 5%. As for the total porosity of the soil, the effect of the plow type was greater than the depth, and the greater the depth than the forward speed, as the total porosity reached (43, 41, and 35) % for the moldboard, disc, and chisel plow, respectively. The increase in depth led to a decrease of 7%, and the increase in velocity led to a decrease of 4% in the index of total soil porosity. As for the predicted results, the amount of convergence between the field calculated and predicted results was (96, 95, 95) % for soil penetration resistance, bulk density, and total soil porosity, respectively.


Introduction
Soil compaction, due to the heavy traffic of agricultural machinery and vehicles in the agricultural fields, has reduced the production of most agricultural crops all over the world, as soil compaction is a form of the physical characteristics of the soil that indicates the deterioration of the soil condition by changing the structure of the soil and reducing the permeability of water and air and reduces of root penetration [1][2][3][4].It is estimated that around 68 million hectares of soils worldwide are affected by soil compaction from vehicular traffic.Compaction is responsible for soil degradation in Europe (33 1259 (2023) 012127 IOP Publishing doi:10.1088/1755-1315/1259/1/012127 2 million hectares), Africa (18 million hectares), Asia (10 million hectares), and Australia (4 million hectares), and some areas of North America [5,6].Using plows at the same operating depth each season or year can cause compacted layer at the bottom of the furrow [7].Soil strength (strength to penetration) is widely used to measure soil compaction [8 , 9].Soil resistivity showed significant differences in most of the soil layers between all the tillage systems.It was found in an experiment conducted by [10], in a soil with a mixture of clay and silty texture, an increase in the resistance to penetration using the moldboard plow compared to the chisel plow, as it increased after the depth of plowing, and the so-called plow basin was found at a depth of 20 cm using the moldboard plow.He attributed the reason for this to be the soil plowing during two periods of soil moisture content difference, where the first period was dry soil and the other was wet soil, and thus during the drying and wetting cycle, this led to an increase in penetration resistance.[11] explained in an experiment conducted to find out the effect of machines on soil compaction compared to normal plowing with no-till cultivation, an increase in the penetration resistance of the soil was found at a depth of 20-25 cm.The so-called plow basin was found, and the amount of soil penetration resistance reached about 2000 kPa, and the reason for this is due to tilling at one depth and for many periods.[12] confirmed in a study conducted to find out the effect of traditional and reduced plowing on soil properties, where he found a compacted layer at a depth of (28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38) cm called the plow basin, and showed through the use of electronic rays that this layer extends to about 55 cm.The reason for this is plowing at one depth for years and with various agricultural machines, as the soil is subjected to continuous and vertical stresses.The soil bulk density index is an indication of the amount of compaction to which the soil is exposed as a result of the passage of agricultural machinery and equipment.It was found that the use of the reversible ground plow increased soil compaction by increasing the measured bulk density after plowing and the soil moisture was 15% higher than it was before plowing [13].The researchers found that the plowing parameters affected the physical factors of the soil, where plowing using the moldboard plow led to an increase in bulk density by an average of 6% compared to no-till cultivation at a depth of 30-40 cm below the tillage depth (tillage basin) [14].[4] by conducting a simulation of soil compaction and comparison with the measurements taken through the bulk density index under traditional plowing systems, where a good agreement was found in comparison and in the depths of plowing and under plowing, where when found, when the depth increased from 20 cm to 50 cm, the bulk density increased from -1.2 1.5 g / cm3 and it was found that compaction of the soil can reach approximately 1 meter in agricultural soils.Soil compaction can destroy the interlocking pores and thus reduce the hydraulic conductivity and air permeability of the soil [15].Soil compaction decreased soil aeration due to a decrease in air-filled porosity by 13-36%, which affected soil microorganisms [16].Soil porosity showed a significant difference between all tillage systems in the surface and deep soil layers [17].The use of the disc plow in plowing led to an increase in soil compaction and a decrease in the yield of tobacco leaves through an increase in the indicators of bulk density and penetration resistance [18].[19] confirmed, through the data obtained from an experiment to know the effect of plows on soil compaction, that plowing using the moldboard plow and disc plow and plowing annually caused soil compaction at the depth of plowing during 3 years, as the soil penetration resistance reached 3.75 MPa and at a depth of (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) cm.In an experiment conducted by [20] to know the effect of the plowing system using the disc plow on the bulk density and soil resistance to penetration at different depths, an increase in the studied properties was found under the studied plowing systems with increasing depth, and it led to the formation of a compacted layer with a high bulk density at a plowing depth of 20-30 cm, amounting to 1.60 grams./cm 3 .In an experiment by [21] to find out the effect of the plow and the plow basin on the physical properties by using traditional plowing, which included the use of the disc plow at different depths, and by measuring the total porosity of the soil, which can determine the extent of soil compaction and disintegration by knowing its value, whether it is a decrease or increase, respectively.0-5 (cm) amounted to (37-41) %, while its value at a depth of (30)(31)(32)(33)(34)(35) cm amounted to about (23-31) %, when plowing at a depth of 20 cm. and the use of heavy machinery.In a study by [22] to find out the effect of reservoir plowing and other plowing methods on the physical properties of the soil, where it was found that both depth and speed had a significant effect on the soil resistance IOP Publishing doi:10.1088/1755-1315/1259/1/0121273 to penetration, when the tillage depths increased from (0-10) cm, (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) cm, (20) -30 cm.The soil resistance to penetration increased under the chisel plow system by (0.84, 0.95, 0.99) MPa, respectively.The increase in the forward speed led to a significant increase in the soil resistance to penetration at all plowing depths and for the various plowing systems, as it increased by (19,24).(%) at depths (0-10) cm and (10-20)%, respectively.At depth (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), the soil resistance to penetration was less by 11%.At the same depth, the soil resistance to penetration increased with the increase in the forward speed of the tractor and in the same proportions.In an experiment conducted by [23] to find out the effect of plows and sunflower plants on the physical properties of the soil, using a plow digger with a depth of (24-26) cm and disc harrows with a depth of (10-20) cm, it was found that the change in bulk density under all depths Tillage systems in the soil layers have increased the bulk density, which indicates an increase in soil compaction, albeit slightly, where the share of the tillage systems had the greatest impact by 64.39%, then the yield by 18.14%, and the depth by 6.49%.The research aims to study the negative effect of primary plowing equipment (moldboard plow, disc plow, and chisel plow) on soil compaction parameters (bulk density, porosity, and soil penetration resistance).In addition to the use of intelligent computing including the use of Design Expert software to develop mathematical models to predict and simulate soil compaction and evaluate the effect of the studied factors on soil compaction.

The Site of the Experiment
The field experiment was conducted in the College of Agriculture -University of Basra in the Karma Ali complex located in the south of Basra city, which is located geographically at longitude 45' 02' 470 north and latitude 33' 30' 300 east, as attached in Figure No. (1).The soil was of silty clay texture.The initial samples were taken for the physical and mechanical measurements of the primary soil in the field, which includes soil texture, soil moisture content, bulk density, true density, and soil resistance to penetration before conducting the experiment, by identifying five sites in the form of the letter X, which cover all areas of the field, taking samples and using Three repetitions for three depths (0-10), (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) cm, and according to the scientific methods used in taking measurements and field and laboratory analyzes.The preliminary results were obtained as attached in Table (1).

The Plows Used in the Experiment
Three types of plows were used: moldboard plow, disc plow, and chisel plow.The moldboard plow was of the hanging type.It had three bodies, the height of the plow was 95 cm, and the working width was about 135 cm.As for the disc plow contains three discs.The disc angle is 45 degrees and the disc inclination angle is 25 degrees.The plow is of the hanging type.The height of the plow is about 90cm, while the working width is 105 cm.While the chisel plow contains 7 shanks, the height of the plow is (100) cm, and the working width is (200) cm, as sh own in Figure (2).

Soil Penetration Resistance
The soil penetration resistance index was measured using the Penetroloagger (electronic penetration resistance) of Dutch origin and produced by Eijkelkamp Agrisearch Equipment, where it measures per 1 cm and using a lathe with a base area of 20 cm2 and an angle of 30 degrees.Preliminary measurements were taken at depths (0-10, 10-20, 20-30) cm, before starting the experiment in the field and obtaining the results as shown in Table (1).After that, the device was used to measure the penetration resistance after plowing and using various plows.Measurements were taken at depths (15-25, 25-35, 35-45) cm in relation to the first depth of 15 cm to know the effect of the plow weapon for every 30 cm below the depth of plowing the weapon, and so on for the two depths.The others were  (20,25) cm, where the plowed soil was displaced and measurements were taken under the plowing depths.

Dry Bulk Density (ρb)
The bulk density of the soil was measured using the known-size cylinder method (Core Sampler) and according to equation (1), after drying the soil samples in the electric oven at 105 degrees for 24 hours until the weight was fixed and according to the method used by [24].The initial measurements were taken at depths of (0-10, 10-20, and 20-30) cm, with three repetitions for each depth before plowing, as the results are shown in Table (1).After the plowing process, the bulk density of the soil was taken at depths (15-20, 20-25, 25-30) cm, where the measurements were taken under the plows directly, with three repetitions for each depth.
Whereas: ρb = bulk density of soil (g/cm 3 .( Ms = mass of dry particles (grams(.V = the total volume of the soil and represents the volume of the cylinder (cm 3 ).

Particle Density (ρs)
The particle density of the soil was measured using the pycnometer method developed by Barsher and reported in [24].It is calculated using Equation (2).The results are as shown in Table (1).

Total Porosity (f)
The total porosity of the soil was calculated using Equation No. (3) and according to the method mentioned in [24].The results are as shown in Table No. (1).

Design Expert Software
After completing the practical part and collecting research data, data processing begins using software Design Expert, which is one of the modern and advanced programs (Version: 8.0.6.1) with enormous capabilities in handling data.It analyzes the data statistically and determines its significance at different levels, providing an ANOVA table.Additionally, it plots relationships between research inputs and outputs and provides a predictive equation for each output.This was stated by [25].

Statistical Analysis
The GenStat software was used to perform statistical analysis and compare the results with the Design Expert software to determine the degree of convergence between the results.This software also performs statistical analysis of the data, determines the significance levels, and provides an ANOVA table.

Soil Penetration Resistance
The results of the analysis of variance in Table (2) show the effect of the studied factors on the index of soil resistance to penetration, where the effect of each of the factor of the type of plow used (moldboard plow, disc plow, chisel plow) and the factor of plowing depth is highly significant between plow type and plowing depth, plow type factor and forward speed, plowing depth factor and forward speed of the tractor had a significant effect on the soil penetration resistance under a significant effect of 5%. Figure (3) shows the effect of each of the factors of the type of plow used and the depth of plowing (15,20,25) cm, and the interaction between the two factors on the characteristic of soil resistance to penetration at speed of 0.45 m/s.It found an increase in soil resistance to penetration using different types of plows, but with varying values between them.Soil penetration resistance increased under the share of the moldboard plow when compared with the disc plow and the chisel, respectively, reaching 3.17 MPa, 2.74 MPa, and 2.61 MPa, respectively.The reason for the difference in the amount of soil resistance to penetration between the types of plows is due to the nature of the design of the plow share.The moldboard plow cuts and separates the soil slice and then carries it to the surface of the moldboard and then turns it over, and all of this is a group of vertical and horizontal forces that the cut soil exerts on the surface of the plow.This force is reacted in response from three sources, the first is the pulling force of the plow coming from the tractor, the second is the opposite edge of the plow blade, which rests on the bottom of the groove when cutting the soil slice, and the third, very important, is the support that stabilizes the plow during plowing, as it applied force to the bottom of the groove and thus increased soil compaction and increased soil As for the disc plow, it works on cutting the soil through the rotation of the share disc and cutting the slice with the edge of the blade.Here, the soil exerts a force on the surface of the disc, especially the sharp edge.In addition to the weight of the disc, and thus the reaction comes by resting the inner edge of the disc on the bottom of the groove, thus increasing soil compaction and thus increasing in the amount of soil resistance to penetration.As for the chisel plow, it cuts the soil through the blade with a small surface area connected to the soil, so the compaction process is minimal and comes from the process of pushing the soil forward and thus applying pressure on the split soil section, and this causes compaction on the layer under the plow, so we find an increase in the resistance of the soil to penetration, but in a way Less compared to rotary and disc rotor plows, these results are consistent with previous studies, including [17,26], who showed an increase in soil penetration resistance when using different types of plows.
3) also shows the depth of plowing depends on the characteristic of soil resistance to penetration, where the increase in the depth of plowing from 15 to 20 and then to 25 cm led to an increase in the soil resistance to penetration and according to the type of plow, as the increase reached 2.64 to 2.70 and then to 3.17 MPa on respectively.For the moldboard plow, this increase also included the other two disc plows and the chisel plow, respectively.This increase in the soil resistance to penetration comes from the increase in the soil resistance of the plow weapon with depth by increasing the volume of the soil stirred up, which affects in several directions on the plow weapon, causing the formation of a layer under the plow with a high resistance called the plow basin.These results are consistent with previous studies where [12,27] confirmed the increase in soil resistance with increasing depth and with different plowing systems.The increase in soil resistance to penetration through the increase in the plowing depth of the other two disc and chisel plows, respectively.Figure (3) also shows the effect of the bilateral interaction between the two factors, plow type and plowing depth, on soil resistance to penetration.The difference in the type of plow and the increase in the depth of plowing led to an increase in the index of soil resistance to penetration, as it gave the lowest amount of soil resistance to penetration for the depth of 15 cm and for the chisel plow, and its value was 2.39 MPa.While the highest soil penetration resistance was 3.17 MPa for the disk plow at a depth of 25 cm.This difference is due to the nature of the work of the plow in the amount of exposure to greater resistance by the soil during the plowing process, as well as the surface area under the surface of the plow share that is in contact with the bottom of the groove, and also that plowing has an important role in this increase through the volume of soil that is dismantled.These results are consistent with previous studies, where [28] where it was found that the soil resistance to penetration increased by increasing the depth of plowing and for the various types of plows, and the reason for this is due to the fact that the intensity of plowing causes fragmentation of soil particles and their compaction with each other and the effect of the large weight of agricultural machinery and equipment compacting the soil.Figure (4) shows the single effect of each factor of the type of plow and the forward speed of the tractor on the indicator of soil resistance to penetration and the combined effect of the interaction of the two factors at a plowing depth of 15 cm.The difference in the type of plow led to an increase in the soil's resistance to penetration, as the moldboard plow gave the highest amount of all types of speeds, as it reached at the first speed 0.45 m/s, the penetration resistance of 2.61 MPa, then the disc plow, where the soil resistance to penetration was 2.41 MPa.As for the chisel plow, the soil penetration resistance was 2.34 MPa.This difference in the amount of soil resistance to penetration is due to the weight of the plow and the operating conditions of the plow, as the moldboard plows make the soil incision and turn it over, and therefore the amount of soil carried on the plow is greater in size, and therefore the pressure on the bottom of the plow increases and the amount of resistance increases.
The results are consistent with [17 , 26]. Figure ( 4) also shows the effect of the forward speed of the tractor on the characteristic of soil resistance to penetration, so that the increase in the forward speed of the tractor from 0.45 to 0.75 and then to 1.05 m/s led to an increase in the soil resistance to penetration according to the type of plow.

A: plow type 1-Moldboard plow 2-Disc plow 3-Chisel plow
The increase was from 2.34 to 2.54 and then to 2.78 MPa, respectively, for the chisel plow.It is the least increase in the amount of soil resistance to penetration compared to the amount of increase for the two moldboard and disc plows, respectively.The reason for this increase is that by increasing the forward speed of the tractor, it leads to an increase in the acceleration of the plowed soil particles, and thus the fragmentation of the soil as a result of the collision of these particles gatherings with each other on the one hand, and on the other hand, their collision with the plow share, quickly and through the downward movement of the fine soil particles.Increasing the intensity of plowing with the increase in the forward speed leads to the fragmentation of soil particles and their compaction with each other, and the effect of the weight of the plow also works to increase the compaction at the bottom of the plow share.These results are consistent with previous studies, where [22 , 28] by increasing the forward speed of the tractor, the penetration resistance of the soil increases.The increase in the soil resistance to penetration through the increase in the forward speed of the tractor with the other two, chisel and disc plows, respectively.Figure ( 4) also shows the effect of the interaction between the two factors, the type of plow and the forward speed of the tractor.The difference in the type of plow and the increase in the forward speed of the tractor led to an increase in the soil resistance index to penetration, as the greatest increase in the soil resistance to penetration was at the working depth of 15 cm for the moldboard plow and the third forward speed of 1.05 m/s by 3.17 MPa.While the lowest soil resistance to penetration of the backhoe plow was recorded at the lowest forward speed of the tractor 0.45 m/sec, which was 2.34 MPa.Where the results show that the speed has a clear effect according to the type of plow.It gave different results for the amount of soil resistance to penetration, where by increasing the speed, it gave the highest amount for the overturned moldboard plow, because of the effect of speed in increasing the compaction of soil particles with each other, and also to increase the surface area of the moldboard plow facing the bottom of the groove, and for the weight of the large plow worked on compacting the soil below the depth of plowing.Thus, the value of soil resistance to penetration is increased.This increase included the disc plow by a lesser amount than the plow because the plow share is a rotating disc that compacts the soil through the rear space of the edge of the disc and also to increase the speed and weight of the plow.These common factors led to an increase in the amount of soil resistance to penetration, while the chisel plow has less effect because of its work on dismantling the soil without turning it over, and thus less harmful to the soil under the depth of plowing.These results are consistent with both [22 , 29 , 30]. Figure (5) shows the effect of the forward speed of the tractor, the depth of plowing, and the interaction between the two factors on the soil resistance to penetration at the third factor, the fixed type of the moldboard plow.When the forward speed and depth decrease, the soil resistance to penetration decreases.Where, at a speed of 0.45 m/s and a depth of 15 cm, it reached 2.71 MPa, while the soil resistance to penetration increased with the increase in the depth of plowing and the forward speed, reaching 4.53 MPa, with an increase of 67% at a depth of plowing of 25 cm and a forward speed of 1.05 m/s.The reason for the decrease and increase in the amount of soil resistance index to penetration is that with a decrease in the plowing depth, the amount of soil that will affect and shed resistance on the plow share will decrease.Thus, the amount of compaction of the soil under the plow blade will decrease, adding to it the effect of the speed, which when its amount decreases, leads to a reduction in the displacement of the soil downward and forward at high speed and reduces soil compaction.On the contrary, the increase in the forward speed and the depth of plowing leads to an increase in the resistance of the soil during plowing, which puts more pressure on the plow share, which is counteracted by the reaction of the arm rest on the bottom of the plowing groove and the pulling force of the tractor.Thus, increasing the compaction of the soil under the plow share, and in addition to the effect of speed by accelerating the dismantling of the soil and moving it forward, and thus compacting the soil.These results are consistent with the findings of previous studies [10 , 31].
The increase in the penetration resistance of the soil by the effect of increasing the plowing depth and the forward speed of the disc plow and the chisel plow, respectively.

Bulk Dry Density
The results of the variance analysis in Table (2) show the effect of the studied factors on the bulk density index of soil, where the effect of each of the factor of the type of plow used (moldboard plow, disc plow, and chisel plow) and the factor of plowing depth and the overlap between the type of plow and the depth of plowing were highly significant.The speed factor and the bilateral interactions between the type of plow and the plowing depth, the factor of the type of plow and the forward speed of the tractor had a significant effect on the bulk density of the soil under the influence of a significant 5%. Figure (7) shows the effect of each of the factors of plow type, depth, and the interaction between the two factors on the characteristic of the bulk density of the soil at the third constant speed factor of 1.05 m/s.Where the use of plows of different types led to an increase in the amount of the aforementioned characteristic, where we find that the moldboard plow gave the highest value of bulk density compared to the disc plow and the chisel plow, respectively.Where the bulk density was 1.52, 1.48 and 1.43 g/cm 3 for each of the moldboard, disc and chisel, respectively, when plowing 15 cm.The reason for the difference in the amount of the aforementioned characteristic is that the moldboard plows work to cut the soil slice and then turn it over, and thus apply greater pressure by the blade on the bottom of the plowing groove for reasons including the large weight of the plow as well as to increase the area that is in contact with the bottom of the groove, which works to increase soil compaction thus, the bulk density increased.These results are consistent with previous studies, where [13,32] found an increase in the bulk density of the flap and disc plows below the plowing depth through the formation of the so-called plow basin.They attributed the reason for this to the difference in soil moisture, as well as the frequent annual use of the above-mentioned plows.As for the chisel plow, it will have less effect on the bulk density of the soil because the plow cuts the soil without turning it over, and thus the compaction of the soil is less.Figure ( 7) also shows the effect of the plowing depth on the bulk density of the soil, where the increase in the plowing depth from 15 to 20 and then 25 cm led to an increase in the bulk density of the soil.Where the increase was from 1.52 to 1.53 and then to 1.68 g / cm 3 , respectively, for the moldboard plow.While the increase for the disc plow was from 1.48 to 1.50 and then to 1.52 g/cm 3 , respectively.As for the chisel plow, the increase in the bulk density of the soil increased by 1.43 to 1.46 and then to 1.48 g/cm 3 , respectively.This increase in the value of the bulk density of the soil with the increase in depth is due to an increase in the volume of the soil stirred up, which causes an increase in the pressure exerted on the plow share, especially for the moldboard plows.From the reaction of the soil on the cutting, as well as the weight of the soil slice carried on the blade.Thus, this force is applied to the bottom of the groove, which is confronted by the reaction of the soil, and thus the bulk density of the soil increases below the plow's share, and thus an increase in the amount of soil compaction.As for the chisel plow, it cuts the soil without turning it over, so the amount of soil that the plow share is exposed to is less, but the resistance of the soil reaction to cutting is encountered, and therefore the pressure on the bottom of the groove is less than the two turning plows, so the compaction of the soil is reduced by giving the least amount of bulk density.These findings are consistent with previous studies where [14,23], that using the last plows led to an increase in the soil bulk density index with increasing depth.The increase in the bulk density of the soil by the effect of increasing the plowing depth factor includes both the disc and the chisel plow, respectively.Figure ( 7) also shows the effect of the overlap between the type of plow and the depth of plowing with the bulk density index of the soil, where we find that the difference in the type of plow and the increase in the depth of plowing led to a clear increase in the bulk density of the soil, as the increase in the depth of plowing using the moldboard plow led to recording the highest value of the mentioned indicator It was 1.68 g/cm3.While the lowest value of the bulk density of the soil when using the chisel plow when plowing at a depth of 15 cm was 1.43 g / cm3.This difference in the amount of soil bulk density is due to the nature of the work of the plow share and to the effect of increasing the depth by increasing the volume of loose soil.These results are consistent with previous studies [4].Figure (8) shows the effect of each of the factors of the type of plow and the forward speed of the tractor and the interaction between them on the bulk density of the soil at the first fixed depth factor of 15 cm.The use of the moldboard plow led to an increase in the bulk density of the soil compared to the disc plow and the chisel.Soil bulk density was 1.43, 1.41, and 1.40 g/cm3 for each of the moldboard, disc plows, and chisel, respectively, at a depth of 15 cm.The difference in the amount of soil bulk density between the types of plows is due to the fact that the moldboard plow works to cut the soil slide and overturn it, and thus increase the volume of soil accumulated on the plow blade, which leads to an increase in soil compaction at the bottom of the plow blade.As for the decrease in the size of the chisel plow, it is due to its action on stirring the soil without turning it over, so the soil resistance on the plow share decreases, and thus its effect on soil compaction is less.These results are consistent with previous studies [17].Figure ( 8) also shows the effect of the forward speed of the tractor on the bulk density index of the soil, where we find that with the difference in the front speed of the tractor, the increase in the amount of the last factor led to an increase in the amount of the bulk density of the soil.When the speed changed from 0.45 to 0.75 and then to 1.05 g / cm 3 for moldboard plow, it led to an increase in the bulk density of the soil and according to the type of plow.This increase is due to the fact that by increasing the forward speed of the tractor, it works to increase the cutting of the soil and stir it up faster, and thus stir the soil faster, and this requires greater force from the plow share, because it also carries the soil slice and turns it over, and by that more force is applied to the bottom of the groove and thus increasing the amount of density.These results are consistent with previous studies by [22,27 , 33].The increase in the bulk density of the soil with the increase in the forward speed of the tractor for the plows included the disc and the chisel, respectively.Figure ( 8) also shows the effect of the interaction between the factors of the type of plow and the forward speed of the tractor on the characteristic of the bulk density of penetration, so we find that with the difference of the type of plow and the increase in the forward speed of the tractor, there is an increase in the bulk density index of the soil, where the plow gave the moldboard plow and at the highest forward speed of the tractor 1.05 m/ The second largest bulk density amounted to 1.52 g / cm3, while the lowest bulk density was recorded at the first speed 0.45 m / s and for the chisel plow, which amounted to 1.40 g / cm 3 .
Figure 8.The effect of plow type A, the forward speed of the tractor C (m/s), and the effect of their interaction on the bulk density of soil (g/cm 3 ).
Figure (9) shows the effect of the interaction between the two factors, the depth of plowing and the forward speed of the tractor, on the soil bulk density index.The results showed that when the depth and the forward speed of the tractor decreased, the bulk density of the soil decreased, as at a speed of 0.45 m/s and a depth of 15 cm, it reached 1.43 g/cm 3 .While the bulk density of the soil increased with the increase of plowing depth and forward speed, reaching 1.68 g/cm3, with an increased rate of 18% at a plowing depth of 25 cm and forward speed of 1.05 m/s. Figure (10) shows the relationship between field-calculated values and expected values.The predicted soil bulk density values were found by determining the main factors in the experiment represented by the type of plow (moldboard, disc, chisel), the forward speed of the tractor, the depth of soil plowing, and its overlaps.This relationship is represented by a final equation for the main factors as in Equation ( 5) with the best Prediction performance with a determination coefficient of R2 = 0.9525.

Soil Porosity
The results of the analysis of variance in Table (4) indicate the effect of the studied factors on the percentage of total soil porosity.The type of plow, depth, and the interaction between the type of plow 1259 (2023) 012127 IOP Publishing doi:10.1088/1755-1315/1259/1/01212714 and depth had a significant effect, while the forward speed of the tractor and the interaction between the type of plow and forward speed were statistically significant below the 5% level on the trait of total soil porosity.Figure (11) illustrates the effect of the type of plow, depth of plowing, and their interaction on the percentage of total soil porosity when the third variable, the forward speed of the tractor, was fixed at 0.45 m/s.The figure shows that the variation in the type of plow resulted in a difference in the percentage of total soil porosity, with the chisel plow giving the highest value of total porosity, reaching 46% compared to the disc plow and moldboard plow, which recorded 45% and 44%, respectively, at a depth of 15 cm.The difference in the amount of porosity between the types of plows is due to the fact that the chisel plow works by disturbing the soil without turning it, thereby reducing its effect on the bottom of the plow by reducing the apparent density of the soil, which has an inverse relationship with the total porosity.On the other hand, moldboard and disc plows have a greater effect on the soil during plowing, as they cut and turn a slice of soil, increasing the pressure on the bottom of the plow due to the large volume of soil being stirred.As a result, porosity decreases by increasing the proximity of soil particles to each other.These results are consistent with previous studies by [22,34] Figure (11) also illustrates the effect of tillage depth on the overall soil porosity, where a decrease in tillage depth led to an increase in porosity for all types of plows.When the depth was reduced from 25 to 20 and then to 15 cm, the porosity increased, reaching 43%, 44%, and 46%, respectively, for the chisel plow.This decrease in total porosity is attributed to the fact that increasing the tillage depth increases the volume of soil that is broken up, as well as the soil density through tillage.As a result, the soil resistance to the cutting action of the plow increases, as well as the vertical forces exerted on the plow blade, which increases the pressure at the bottom of the furrow, thereby increasing the bulk density.This acts inversely with the percentage of total porosity, where the porosity decreases.These results are consistent with previous studies by [20,31,35] which confirmed that an increase in bulk density under different tillage systems leads to a decrease in total soil porosity with increasing tillage depth.This decrease also occurs with the other types of plows, including the disc plow and moldboard plow, respectively.Figure (11) also demonstrates the effect of interaction between the factors of plow type and plowing depth on the total soil porosity.The interaction between the Chisel plow and a plowing depth of 15 cm resulted in the highest total soil porosity, reaching 46%.Conversely, using the chisel plow at a depth of 25 cm led to the lowest percentage of total soil porosity, reaching 39%.The reason for the difference in porosity values is attributed to the action of the moldboard plow, which disturbs the soil without inverting it.Furthermore, at a shallower depth of 15 cm, the amount of disturbed soil is less, thus reducing the plow's effect on the furrow bottom and decreasing the apparent density while increasing the total soil porosity, which is the opposite effect of apparent density.In contrast, the effect of the chisel plow is significant on the total soil porosity, resulting in lower porosity values.The effect of greater plowing depth of 25 cm is also significant, where the chisel plows slice and invert the soil, and the volume of cut soil increases with depth.Therefore, the plow's effect is greater at the bottom of the plowing depth, increasing the apparent density and decreasing the total soil porosity.These results are consistent with previous studies by [21 , 35] which revealed a high-density layer called the plow pan beneath the traditional plow at greater depths.Figure (12) illustrates the effect of plow type, forward speed of the tractor, and their interaction on the percentage of total soil porosity at a constant depth of 15 cm.As shown in the figure, the type of plow has a clear effect on total porosity, as evidenced by the variation in its value with different plow types.The chisel plow gave the highest value for this property, reaching 44%, while the disc plow was lower at 43%, and the moldboard plow gave the lowest value at 41% at a forward speed of 1.05 m/s.This difference in porosity is due to the combined effect of several factors, such as plow weight, the action of the plow blade, the working width of the plow blade, and physical factors such as moisture and organic matter.Increasing the weight of the plow affects soil compaction by increasing the proximity of soil particles to each other.The nature of the plow blade also plays a role, where the subsoil plow only disturbs the soil without turning it over, resulting in less resistance from the soil and a lower reaction on the plow blade, resulting in less soil compaction under the plow depth.On the other hand chisel plows flip and turn over the soil, increasing the impact of the blade on the soil and resulting in greater soil compaction under the plow.Moisture also contributes to soil compaction by reducing the bonds between soil particles through increasing the size of the water film around the soil particles, resulting in increased soil density and decreased total porosity.These results are consistent with previous studies conducted by [34]. Figure 12 also demonstrates the effect of the forward speed of the tractor on the total porosity of the soil.The figure shows that as the forward speed decreases, the total porosity of the soil increases.
When the speed decreased from 1.05 to 0.75 and then to 0.45 meters per second, the total porosity of the soil increased from 41% to 43% and then to 45%, respectively, with a percentage increase of 5% and 5% for the moldboard plow and reversible plow, respectively.The reason for this increase in total porosity of the soil with a decrease in the forward speed of the tractor is due to the decrease in the pressure that the plow tools are subjected to from the size of the soil particles that are being stirred.This allows the soil to be pushed and the plowing force on the cut soil is reduced, resulting in the particles not being pushed too quickly to collide with each other and pile up, leading to a decrease in the apparent density, which has an inverse relationship with the total porosity.These results are consistent with previous studies by [22 , 33], who confirmed that an increase in speed resulted in an increase in the apparent density due to the breakdown of soil particles into finer particles, which reduces the size of pores in the total volume, and thus increases the apparent density and the soil piling.This decrease with increasing forward speed applies to the other plows as well, including the reversible disc plow and the reversible chisel plow, respectively.

A: plow type 1-Moldboard plow 2-Disc plow 3-Chisel plow
Figure (12) illustrates the effect of the interaction between forward speed of the tractor and the type of plow on the total porosity index of soil.The highest percentage of total porosity was obtained with the chisel plow and the lowest forward speed of 0.45 m/s, reaching a value of 46%.Meanwhile, the total porosity of the moldboard plow and the highest forward speed of 1.05 m/s was 41%.The difference in the percentage of total porosity of soil is attributed to the combined effect of the type of plow and the forward speed, where the direct effect of lowering the speed while using the chisel plow, which works on stirring the soil without turning it, combines with the reduced speed that leads to a decrease in the acceleration force of soil displacement.These factors reduce the soil compaction by decreasing the apparent density of soil and thus increase the total porosity of the soil.On the other hand, the combination of the moladboard plow's dumping and overturning actions with an increase in speed, which increases the acceleration force of soil displacement, leads to an increase in the minute soil particles' accumulation beneath the plow's depth, resulting in an increase in the apparent density of soil.The latter is inversely proportional to the porosity of soil and thus reduces the total porosity of soil.These results are consistent with previous studies by [22 , 33]. Figure (13) illustrates the effect of the interaction between two factors, namely plowing depth and tractor forward speed, on the total porosity of the soil under the assumption of a fixed third factor, which is the type of plow (reversible moldboard plow).The figure shows that as plowing depth and tractor forward speed decrease, the total porosity of the soil increases.For example, at a forward speed of 0.45 m/s and plowing depth of 15 cm, the total porosity reached 45%.On the other hand, the total porosity of the soil decreases as plowing depth and tractor forward speed increase, reaching 35% at a plowing depth of 25 cm and a forward speed of 1.05 m/s, which represents a 29% increase compared to the previous condition.
The reason for the increase or decrease in the total porosity index of the soil is related to the amount of soil that will be affected by the plow resistance, which decreases with the decrease in plowing depth.This means that the amount of soil displaced below the plow will be less, and hence the soil compaction will decrease, resulting in an increase in the total porosity of the soil.In contrast, increasing the forward speed and plowing depth leads to an increase in soil resistance during plowing, which exerts greater pressure on the plow blade that is countered by the plow support on the bottom of the furrow and the tractor pulling force.This results in an increase in the soil displacement and hence an increase in the soil compaction, leading to a decrease in the total porosity of the soil.These results

A: plow type 1-Moldboard plow 2-Disc plow 3-Chisel plow
are consistent with previous studies by [21,2,23,29,36].Moreover, the increase in the total porosity of the soil was observed for both the reversible disc plow and the chisel plow, respectively.
Figure 13.The forward speed of the tractor C (m/s), plowing depth B (cm), and the effect of their interaction on the percentage of the total porosity of the soil (%).

The Relationship Between Field-Calculated and Predicted Soil Resistance to Penetration
The total porosity values of the predicted soil were determined using Design Expert software by identifying the main factors in the experiment, which consisted of the type of plow (moldboard, disc, chisel), plowing depth, and tractor forward speed, as well as the interaction between these factors.The relationship between these factors was represented by a final equation, as shown in equation ( 6), which provided the best prediction performance with a determination coefficient (R2) of 0.9515.Figure (14) illustrates the relationship between the experimentally determined values and the expected values calculated from the software's coefficient with the same determination coefficient (R2 = 0.9515).

Conclusions
 The use of chisel plows led to lower soil compaction under the plow blades, as indicated by a decrease in soil penetration resistance, bulk density, and an increase in total porosity.The use of moldboard plows increased soil penetration resistance, bulk density, and total porosity, and this increase was higher than that of disc and chisel plows.However, the disc and chisel plows had lower bulk density and total porosity and soil penetration resistance compared to moldboard plows.Therefore, using the chisel plow system is better as it reduces soil compaction indicators (bulk density, total porosity, and soil penetration resistance). Plowing at a depth of 15 cm increased soil penetration resistance, bulk density, and total porosity, while plowing at a depth of 25 cm increased soil penetration resistance and bulk density and decreased total porosity. Using a forward speed of 1.05 m/s increased soil penetration resistance and bulk density and decreased total porosity, while using a forward speed of 0.45 m/s decreased soil penetration resistance and bulk density and increased total porosity for all types of plows used. The interaction between plowing depth and tractor forward speed had the most significant impact on soil compaction indicators (bulk density, soil penetration resistance, and total porosity). The predicted values showed good agreement with the field-measured and simulated soil compaction indicators (bulk density, total porosity, and soil penetration resistance), with a determination coefficient of 96%.

Figure 3 .
Figure 3.Effect of plow type A, plowing depth B (cm), and the effect of their overlap on the soil resistance to penetration.

Figure 4 .
Figure 4.The effect of plow type A, the forward speed of the tractor C (m/s), and the effect of the interaction between them on the soil resistance to penetration.

Figure 5 .
Figure 5.The forward speed of the tractor C (m/s), plowing depth B (cm), and the effect of the interaction between them on the soil resistance to penetration.

Figure ( 6 ) 10 Figure 6 .
Figure(6) shows the relationship between the field-calculated values and the expected values calculated.Soil resistance values for predicted penetration were found by determining the main factors in the experiment represented by the type of plow (moldboard, disk, and chisel), plowing depth, the forward speed of the tractor and the overlap between them.This relationship is represented by a final equation for the main factors as in Equation (4) with the best Prediction performance with a determination coefficient of R2 = 0.9574.

Figure 7 .
Figure 7. Effect of plow type A, plowing depth B (cm), and the effect of their overlap on soil bulk density (g/cm 3 ).

13 Figure 9 .
Figure 9.The forward speed of the tractor C (m/sec), plowing depth B (cm), and the effect of the interaction between them on the bulk density of the soil (g/cm 3 ).

Figure 11 .
Figure 11.Effect of plow type A, plowing depth B (cm), and the effect of their overlap on the percentage of soil porosity (%).

Figure 12 .
Figure 12.Effect of plow type A, forward speed of tractor C (m/s), and the effect of their interaction on the percentage of soil porosity (%).

Figure 14 .Final
Figure 14.The relationship between the field-calculated percentage of total soil porosity and the predicted percentage of total soil porosity.

Table 1 .
Primary physical and mechanical properties of soil.

Table 2 .
Analysis of variance for tabular F values for the studied traits.