The effect of tillage direction on soil redistribution by mouldboard ploughing on complex slopes

Seven mouldboard ploughing experiments were conducted to systematically investigate the effect of different tillage directions on soil redistribution on hillslopes. The present study included tillage directions other than parallel to the gradient or along the contour, that is, in our experiments the slope gradient changed simultaneously in tillage and in turning direction. Using physical tracers we developed a model of the two-dimensional tracer displacement as a function of topography and tillage variables. The displacements in tillage and in turning direction were separately described as 2nd degree polynomials in both tillage and in turning directions. This model fully accounted for the directionality of tillage. Displacement in turning direction additionally depended on tillage depth, while that in tillage direction was affected by tillage speed and soil bulk density. We found a large effect of tillage directionality on soil redistribution, and tillage at 45° to the gradient turning soil upslope was the least erosive tillage direction. We obtained non-linear relationships between soil redistribution and profile curvature, instead of the linear relationships reported previously. Consequently tillage erosivity varied in tillage direction and a unique tillage transport coefficient could not be obtained for all tillage directions.     

Investigation into the effect of tillage on solute movement to drains through a heavy clay soil

Abstract. Eight lysimeters, each with a surface area of 0.5 m² and a length of 60 cm, were taken over mole drains from a Denchworth soil and divided into two groups with either a standard agricultural tilth or a finer, deeper topsoil tilth. They were variously instrumented to measure soil moisture content at three depths and losses of nitrate, a bromide tracer and radiolabelled isoproturon, all of which were followed over a year. Leaching of isoproturon was initiated by artificial irrigation either 1 or 39 days after application. The finer tilth seemed to increase the water-holding capacity of the topsoil, and this resulted in slower wetting of the subsoil, decreased flow volumes from the first events of the season and a delay of approximately four weeks in the time to the maximum concentration of the bromide tracer in leachate. The finer topsoil tilth also decreased maximum concentrations of isoproturon from 29 to 15 μg l⁻¹ following irrigation 1 day after treatment and from 43 to 9 μg l⁻¹ following irrigation 39 days after treatment. Total losses of isoproturon were three times larger with the standard agricultural tilth. Differences were attributed to a decrease in bypass flow through the topsoil with the finer tilth, particularly during events early in the season. There was a small decrease in total losses of nitrate in leachate from the finer tilth compared to that from the standard tilth.     

Draught and vertical forces obtained from dynamic soil cutting by plane tillage tools

An understanding of the relationship between tool forces and speed is important in evolving management strategies for optimum performance. The effect of speed on tillage tool forces were studied experimentally for wide (width=25.4 cm, depth=15 cm) and narrow (width=5.1 cm, depth=22.9 cm) plane tillage blades operating in a Dystric Fluvisol (silty sand texture) in a soil bin. The tools were tested at two depths (10 cm and 15 cm for wide blade, 11.4 cm and 22.9 cm for narrow blade), two rake angles (45° and 90°) and eight speed levels (0.25, 0.5, 0.75, 1.00, 1.25, 1.50, 1.75 and 2.00 m/s). The variables were combined in a 2×2×8 factorial experiment with three replications. The performance of three theoretical models based on the trial wedge approach in predicting the experimental results was evaluated. The first model (Model 1), based on Soehne's approach (with modification for the three-dimensional analysis) assumes that the soil fails in a series of shear planes, forming a wedge that is trapezoidal in shape. The equilibrium of the wedge boundary forces produce the force required for failure. The second model (Model 2), based on Mckyes' approach assumes that soil failure is by the formation of a centre wedge flanked by two side crescents. Equilibrium of the boundary forces on the wedge and crescents produce the forces as a function of an unknown failure angle which is obtained by minimizing the weight component of the total force. Model 3, based on Perumpral's approach assumes the same failure wedge as Model 2 but the total cutting force is minimized instead. Experimental results show that the tool force (draught and vertical force) is a function of the speed and the square of speed whereas the three models assume it to be a function of the square of speed only. The models were not very accurate in predicting the experimental results. The average percent deviation of the predicted forces from the observed values were 43%, 40% and 66% for Models 1, 2 and 3, respectively. Thus, Model 2 had more general agreement with experimental observations. The models were better in predicting the forces (draught and vertical force) for the narrow tool with average percent deviations of 33%, 28% and 46% for Models 1, 2 and 3, respectively, as compared to 53%, 51% and 85% for the wide blade.     

耕作引起的紫色土母岩破碎运动定量分析

紫色土区存在耕作破碎母岩补充土壤的现象,尤其是在土层浅薄且岩性松软的泥页岩区,然而目前鲜有相关方面报道。为定量评估不同自然条件和耕作方式下母岩破碎运动特征,以裸露泥岩为研究对象,在野外模拟耕作试验中使用物理示踪法追踪2种含水率(7.44%和14.77%)和5个坡度(5°、10°、15°、20°、25°)条件下,不同深度(2、4、6 cm)耕作引起的母岩破碎运动情况。结果表明:1)含水率是影响母岩破碎运动的重要因素,且耕作深度越小其影响越大;2)随着耕作深度的增大,岩屑的平均位移呈逐渐减小的变化趋势,2 cm深度耕作引起的岩屑位移最大;3)岩屑位移随着深度的增加快速减小,且岩石含水率高的坡面减小幅度更大;4)母岩含水率较高(14.77%)时,坡度对坡面岩屑运动没有显著影响(P>0.1),但母岩含水率较低(7.44%)时,坡度与坡面岩屑位移存在显著正相关关系(P<0.1)。可见,耕作破碎母岩过程受到岩石含水率、耕作深度和坡度的共同影响,且各因子在不同深度的作用机制不同。该研究为揭示母岩人为风化成土和侵蚀机制初步提供了技术支撑和依据。     

Impacts of periodic tillage on soil C stocks: A synthesis

Long-term loss of soil C stocks under conventional tillage and accrual of soil C following adoption of no-tillage have been well documented. No-tillage use is spreading, but it is common to occasionally till within a no-till regime or to regularly alternate between till and no-till practices within a rotation of different crops. Short-term studies indicate that substantial amounts of C can be lost from the soil immediately following a tillage event, but there are few field studies that have investigated the impact of infrequent tillage on soil C stocks. How much of the C sequestered under no-tillage is likely to be lost if the soil is tilled? What are the longer-term impacts of continued infrequent no-tillage? If producers are to be compensated for sequestering C in soil following adoption of conservation tillage practices, the impacts of infrequent tillage need to be quantified. A few studies have examined the short-term impacts of tillage on soil C and several have investigated the impacts of adoption of continuous no-tillage. We present: (1) results from a modeling study carried out to address these questions more broadly than the published literature allows, (2) a review of the literature examining the short-term impacts of tillage on soil C, (3) a review of published studies on the physical impacts of tillage and (4) a synthesis of these components to assess how infrequent tillage impacts soil C stocks and how changes in tillage frequency could impact soil C stocks and C sequestration. Results indicate that soil C declines significantly following even one tillage event (1–11% of soil C lost). Longer-term losses increase as frequency of tillage increases. Model analyses indicate that cultivating and ripping are less disruptive than moldboard plowing, and soil C for those treatments average just 6% less than continuous NT compared to 27% less for CT. Most (80%) of the soil C gains of NT can be realized with NT coupled with biannual cultivating or ripping.     

Measurement and modelling of the effects of initial soil conditions and slope gradient on soil translocation by tillage

Tillage erosion studies have mainly focused on the effect of topography and cultivation practices on soil translocation during tillage. However, the possible effect of initial soil conditions on soil displacement and soil erosion during tillage have not been considered. This study aims at investigating the effect of the initial soil conditions on net soil displacement and the associated erosion rates by a given tillage operation of a stony loam soil. Tillage erosion experiments were carried out with a mouldboard plough on a freshly ploughed (pre-tilled) soil and a soil under grass fallow in the Alentejo region (Southern Portugal).

The experimental results show that both the downslope displacement of soil material and the rate of increase of the downslope displacement with slope gradient are greater when the soil is initially in a loose condition. This was attributed to: (i) a greater tillage depth on the pre-tilled soil and (ii) a reduced internal cohesion of the pre-tilled soil, allowing clods to roll and/or slide down the plough furrow after being overturned by the mouldboard plough.

An analysis of additional available data on soil translocation by mouldboard tillage showed that downslope displacement distances were only significantly related to the slope gradient when tillage is carried out in the downslope direction. When tillage is carried out in the upslope direction, the effect of slope gradient on upslope displacement distances was not significant. This has important implications for the estimation of the tillage transport coefficient, which is a measure for the intensity of tillage erosion, from experimental data. For our experiments, estimated values of the tillage transport coefficient were 70 and 254 kg m⁻¹ per tillage operation for grass fallow and pre-tilled conditions, respectively, corresponding to local maximum erosion rates of ca. 8 and 35 Mg ha⁻¹ per tillage operation and local maximum deposition rates of ca. 33 and 109 Mg ha⁻¹ per tillage operation.     

Influences of tillage operations on soil translocation over sloping land by hoeing tillage

Very few studies have investigated the factors affecting soil displacement and tillage erosion by hoeing tillage. This study adopted a magnetic tracer method to investigate the influences of hoe form and tillage depth on soil translocation over steep hillslopes in Southwest China using a new type of magnetic tracer, i.e., ilmenite powder. Ilmenite powder enhanced the magnetic sensitivity of soil at the end position of tracer distribution, and improved the accuracy and efficiency of tillage translocation measurements. Tillage translocation by wide and perforated hoes was found to be significantly correlated with slope gradient (P < 0.01), however, no significant correlation was found for narrow and bidentate hoe tillage (P > 0.05). Compared with wide hoes, the tillage erosion rates resulting from the use of narrow, perforated and bidentate hoes were reduced by 12.4%, 11.0%, and 16.3%, respectively, indicating that changes in hoe forms resulted in a marked decrease in downslope soil translocation and tillage erosion. Tillage erosion rate decreased by 64% when the tillage depth was reduced from 0.26 to 0.14 m. These results suggest that innovations in hoe form and reductions in tillage depth are important means to manage tillage erosion due to hoeing.     

Prediction of the soil structures produced by tillage

Data are presented for the amount of clods >50 mm produced when five different soils were tilled at a range of different, naturally occurring water contents. The optimum water content for soil tillage is defined as that at which the amount of clods produced is minimum. The amount clods produced at this optimum water content is shown to be linearly and negatively correlated with the value of Dexter's index S of soil physical quality. This results in a rational model for soil tillage that enables predictions to be made for all different soils and conditions. Pedo-transfer functions can be used to estimate the input parameters for the model for cases, for which measured values are not available. It is concluded that for soils with good physical condition (i.e. S > 0.035), no clods >50 mm are produced during tillage.     

The long-term effect of tillage on soil displacement of hilly areas used for growing wheat in Greece

Abstract. Tillage displaces large amounts of soil from upper slopes and deposits soil in lower landscape positions, greatly affecting productivity in these areas. The long-term effect of tillage on soil erosion was studied in four field sites growing mainly rainfed wheat. The soil loss from landscape positions with slopes, ranging from 3 to 28%, was estimated by: (a) comparing data of horizon thickness described at the same position at different times; and (b) using soil movement tracers added to the soil. Existing empirical relationships were used for estimating soil loss by tillage and runoff water, and loss in wheat biomass production. The experimental data showed soil losses of 0.4 to 1.4 cm yr^–1 depending on slope gradient, plough depth, and tillage direction. In two of the sites, soil depth has been reduced by 24–30 cm in a period of 63 years. The mean soil displacement of the plough layer (30 cm thick), measured by soil movement tracers, ranged from 31 to 95 cm yr^–1 depending mainly on slope gradient, corresponding to a rate of soil loss of 0.3 cm to 1.4 cm yr^–1. Soil eroded from the upper slopes was deposited on the lower slopes increasing soil thickness by 0.4 cm to 1.4 cm yr^–1. The application of empirical relationships, estimating soil loss by tillage and water runoff, showed that soil erosion at the field sites can be mainly attributed to tillage. The loss in wheat biomass production due to erosion was estimated at 26% on upper slopes for a period of 63 years, while a 14.5% increase in wheat production was estimated due to deposition of soil material in the lower landscape.     

Dynamics of soil hydraulic properties during fallow as affected by tillage

There is limited information on the effects of tillage practices on soil hydraulic properties, especially changes with time. The objective of this study was to evaluate on a long-term field experiment the influence of conventional tillage (CT), reduced tillage (RT) and no-tillage (NT) on the dynamics of soil hydraulic properties over 3 consecutive 16–18 month fallow periods. Surface measurements of soil dry bulk density (ρ_b), soil hydraulic conductivity (K(ψ)) at −14, −4, −1 and 0 cm pressure heads using a tension disc infiltrometer, and derived hydraulic parameters (pore size, number of pores per unit of area and water-transmission porosity) calculated using the Poiseuille's Law were taken on four different dates over the fallow period, namely, before and immediately after primary tillage, after post-tillage rains and at the end of fallow. Under consolidated structured soil conditions, NT plots presented the most compacted topsoil layer when compared with CT and RT. Soil hydraulic conductivity under NT was, for the entire range of pressure head applied, significantly lower (P < 0.05) than that measured for CT and RT. However, NT showed the largest mean macropore size (0.99, 0.95 and 2.08 mm for CT, RT and NT, respectively; P < 0.05) but the significantly lowest number of water-conducting pores per unit area (74.1, 118.5 and 1.4 macropores per m² for CT, RT and NT, respectively; P < 0.05). Overall, water flow was mainly regulated by macropores even though they represented a small fraction of total soil porosity. No significant differences in hydraulic properties were found between CT and RT. In the short term, tillage operations significantly increased K (P < 0.05) for the entire range of pressure head applied, which was likely a result of an increase in water-conducting mesopores despite a decrease in estimated mesopore diameter. Soil reconsolidation following post-tillage rains reduced K at a rate that increased with the intensity of the rainfall events.     

The effects of long-term conservation tillage, crop residues and P fertilizer on soil conditions and responses of summer and winter crops on an Andosol in Japan

A field experiment was conducted from 1983 to 1992 in Tsukuba, Japan to investigate the effects of tillage on soil conditions and crop growth in a light-colored Andosol. Three tillage methods (NT: no-tillage, RT: no-tillage for summer cropping and moldboard plowing for winter cropping, and CT: conventional rotary tillage to a depth of 15 cm) were employed in combination with crop residue application (+R, −R) and fused magnesium phosphate (FMP) fertilization (+P, −P). Under the combination of NT and +R, diurnal variation of soil temperature at a depth of 5 cm was smaller during the summer cropping season and soil temperature in the daytime was lower during the winter cropping season than under CT. Soil inorganic N concentration at a depth of 0–30 cm was +R > −R and NT > RT > CT. The early growth of summer crops was accelerated under NT in comparison with CT, and yields were higher under NT and RT in comparison with CT. On the other hand, winter crop yields were significantly reduced under NT, while they were still higher under RT in comparison with CT. Yields were higher with +R and +P application, respectively, and these effects were more pronounced in winter cropping. The positive effect of FMP fertilization was greater in combination with NT, and that of residue treatment was greater in combination with RT and NT than with CT. In conclusion, the best tillage practice for Andosols on the Kanto Plain is RT, i.e. a combination of NT for summer cropping and CT for winter cropping. The application of NT for winter cropping is not recommended, although the application of phosphate and crop residues could reduce the risk of yield reduction, because of improved soil nutrient status and moderation of diurnal soil temperature.     

Effects of tillage practices combined with mucuna fallow on soil erosion and water dynamics on Ishigaki Island,Japan

Abstract

This study was conducted on a sloping field at the Japan International Research Center for Agricultural Sciences, Okinawa Subtropical Station, Ishigaki Island, Okinawa Prefecture, Japan, to evaluate the effects of zero tillage farming combined with mucuna fallow as a cover crop on soil erosion and water dynamics. Two fallow systems (natural and mucuna) in combination with two soil tillage treatments (zero tillage and conventional tillage) were imposed on three sloping fields (2.0°, 3.5° and 5.0°). A sorghum crop (Sorghum bicolor (L) moench) was planted after the soil tillage treatment. Soil loss for zero tillage farming combined with mucuna fallow was equivalent to only 3% of that for the conventional tillage farming with natural fallow. Runoff water was also reduced by between 74% and 77% when compared with the conventional tillage system with natural fallow. These results indicate that zero tillage with mucuna fallow is a very effective measure for the control of soil erosion and water runoff. Moreover, this farming system improved water infiltration during both the fallow and the sorghum cropping periods. For the zero tillage plot, water loss as deep percolation increased 1.6-fold compared with that for the conventional farming under heavy rainfall conditions. It is expected that under less rainfall areas or seasons, the effects of zero tillage farming combined with the mucuna cover crop may be more pronounced on water runoff control and, therefore, may greatly improve soil water conditions.     

岩溶区坡地耕作侵蚀过程中的土壤再分布研究

对耕作侵蚀引起的土壤空间再分布进行研究,有利于改革不合理的耕作方式和治理坡耕地水土流失。本文以重庆市中梁山为例用示踪法对坡耕地进行试验研究。结果表明:随着坡度的增大,耕作后示踪剂在示踪区的含量越来越少;它的最大值出现的位置离基线越来越远,值越来越小;沿耕作方向移动的距离越来越远。这种规律性以锄头和铁锹顺坡明显,等高和踩锹顺坡不明显。从本区耕作侵蚀的角度考虑,等高耕作方式明显要优于顺坡耕作;在顺坡耕作中踩锹优于锄头和铁锹。最后还结合岩溶山区特殊的自然环境条件,讨论了耕作侵蚀对石漠化的影响。     

耕作和保墒措施对冬小麦生育时期光合特征及水分利用的影响

为探明不同耕作保墒措施下冬小麦生育期间光合生理特征及其增产机理,采用田间试验,以常规耕作为对照,采用深松、秸秆覆盖、免耕、施用有机肥及保水剂等措施,研究了不同耕作和保墒措施对冬小麦生育期间光合作用、产量及水分利用效率的影响。结果表明:冬小麦光合速率和叶片水分利用效率均以孕穗期最高,而灌浆期最低。蒸腾速率和气孔导度均以扬花期最高。对不同处理而言,在各生育时期均以深松处理的光合速率和叶片水分利用效率最高,其次为秸秆覆盖处理。在拔节期、孕穗期和扬花期以有机肥处理的蒸腾速率最高,而灌浆期以秸秆覆盖的蒸腾速率较高,在全生育期对照的蒸腾速率均较低。气孔导度与蒸腾速率表现规律基本一致。不同耕作、保墒措施均提高了小麦的穗数、穗粒数及千粒重,以及小麦籽粒产量和水分生产效率,降低了小麦总耗水量;各处理中以深松处理的效果最佳,其产量和水分生产效率分别较对照提高19.6%和38.3%。相关分析表明:各时期的小麦光合速率及叶片水分利用效率均与小麦产量和水分生产效率呈正相关,且随生育期的推进,其相关性增强,特别在扬花期,光合速率对于小麦产量和水分生产效率的影响更显著。     

Effect of different tillage systems on soil properties and wheat yield in Middle Anatolia

Field experiments were conducted on a clay soil in entisol to determine the effect of different tillage tools on soil properties, emergence rate index and yield of wheat in Middle Anatolia. There were four different tillage treatments: mouldboard ploughing followed by disc harrowing twice; rotary tillage twice; stubble cultivator followed by a disc harrowing; heavy globe disc twice. The smallest aggregate mean weight diameters and surface roughness were produced by rotary tillage. Decreasing mean weight diameter decreased the surface roughness. There was a significant (P < 0.01) effect of the four different tillage systems on moisture content, bulk density, penetration resistance, aggregate mean weight diameter and surface roughness. Tillage systems had a significant effect on emergence rate and yield of wheat. Emergence rate index and yield of wheat varied from 15.24 to 18.88 and from 3065 kg ha⁻¹ to 4265 kg ha⁻¹, respectively. The greatest emergence rate index and yield were obtained with stubble cultivator followed by disc harrowing treatment.     

Total and mineralizable soil carbon as affected by tillage in the Argentinean Pampas

This study was carried out in experimental plots established at Marcos Juárez, in the Pampean Region (center of Argentina) on Typic Argiudolls, with high silt content. The aim of this work was to study the effects of two tillage systems (reduced tillage and no-tillage) on the amount of total organic C, potentially mineralizable C, C released by respiration, and C stock in the topsoil of a corn (Zea mays L.)–wheat (Triticum aestivum L.)/soybean (Glycine max L. Merr.)–soybean rotation. No-tillage showed C stock greater than reduced tillage only at 0–5 cm depth, but not at 0–20 cm, even though in situ respiration was lower. As a consequence, no tillage did not show a differential capacity for C sequestration in comparison with reduced tillage.     

Influence of tillage on crop residue cover, soil properties and yield components of cowpea in derived savannah ectones of Nigeria

The effects of five tillage treatments: no tillage (NT), disc harrowing (DH), mouldboard ploughing followed by disc harrowing (MPH), disc ploughing followed by disc harrowing (DPH), and disc ploughing followed by two passes of disc harrowing (DPHH) on crop residue cover, soil properties and some yield parameters of cowpea were investigated for a derived savannah ectone soil. The residue left on the soil surface for NT, DH, and MPH is not significantly different. The NT left 32.1 and 44.3% more residue on the soil surface than the DPH and DPHH treatments, respectively. The NT treatment had least average value of soil bulk density of 1.01 g/cm³. The mean soil bulk densities for the DH, MPH, DPH and DPHH vary between 1.20 and 1.35 g/cm³. The soil moisture content decreased with increasing soil depth. At the soil depth of 10–30 cm, the cone penetration resistance at NT was 1.18 MPa compared with 0.92 MPa for the DH treatment, although these were not significant (p≤0.05). The tillage treatments had a significant effect on grain yield, mass of leaves and stems, root length density, and number of pods per plant of cowpea except on the germination count. DH and NT treatments gave different grain yield and number of pods per plant but these values were not statistically different and represent the highest grain yield and number of pods per plant among the other treatments were considered. The root zone exploration revealed highest root density at shallow depths with the DH and MPH treatments.     

The influence of organic matter in reducing the destabilization of soil by simulated tillage

Different agricultural practices can result in a decline in soil organic carbon (SOC) and a consequent reduction in soil structural stability. Experiments were conducted on soils with a range of SOC values, to quantify the destabilizing effects of increased tillage intensity. Different tillage intensity was simulated with the use of a falling weight, where specific energy levels, similar to those experienced during tillage, were reproduced. The level of destabilization was assessed by the quantity of mechanically dispersed clay (using a turbidimetric technique) and the quantity of water-stable aggregates (WSA) > 0.25 mm remaining after being shaken in water.

The quantity of clay dispersed increased with increasing water content, in the absence of any mechanical pretreatment, the rate of increase rising sharply with declining SOC. Following simulated tillage, and at water contents above the plastic limit, clay dispersion increased in proportion to the energy of disruption, and also increased with decreasing SOC levels. Below the plastic limit all the soils were relatively insensitive to mechanical disruption. A simple empirical model was derived to link clay dispersion to SOC, water content and energy of disruption.

The proportion of WSA declined sharply with decreasing SOC, and to a lesser extent following tillage. The quantity of WSA following simulated intensive tillage (300 J kg⁻¹) of grassland (SOC, 2.8–3.2 g (100 g)⁻¹) was greater than that present, prior to tillage from fallow, arable and arable/ley rotation treatments (SOC 1.1–2.5 g (100 g)⁻¹). Aggregate tensile strength was found to be relatively insensitive to differences in SOC. However, variations of strength within treatments, an indicator of soil friability, increased in proportion with SOC. A turbidity index was derived in which the turbidity of natural and remoulded aggregates was compared. Variation of this index with increasing mechanical energy is used as an indicator of the sensitivity of soils to damage during tillage. A visual representation is constructed to link the sensitivity of soils to damage during tillage with both SOC and water potential. These experiments illustrate that management practices, which lead to a long term reduction in SOC, are responsible for an increase in aggregate strength and reduction in stability plus an increase in sensitivity of soils to structural decline following subsequent tillage.     

Wheel traffic impact on soil conditions as influenced by tillage system in Central Anatolia

The increased limiting effects of soil compaction on Central Anatolian soils in the recent years demonstrate the need for a detailed analysis of tillage system impacts. This study was undertaken to ascertain the effects of seven different tillage systems and subsequent wheel traffic on the physical and mechanical properties of typical Central Anatolian medium textured clay loam soil (Cambisol), south of Ankara, Turkey. Both tillage and field traffic influenced soil bulk density, porosity, air voids and strength significantly except the insignificant effect of traffic on moisture content. Traffic affected the soil properties mostly down to 20 cm. However, no excessive compaction was detected in 0–20 cm soil depth. The increases of bulk density following wheel traffic varied between 10–20% at 0–5 cm and 6–12% at 10–15 cm depth. In additions, traffic increased the penetration resistance by 30–74% at 0–10 cm and 7–33% at 10–20 cm. Less wheel traffic-induced effects were found on chisel tilled plots, compared to ploughed plots. Soil stress during wheel passage was highly correlated with soil strength. Also, both tillage and traffic-induced differences were observed in mean soil aggregate sizes, especially for mouldboard ploughed plots. The obtained data imply that chisel+cultivator-tooth harrow combination provides more desirable soil conditions for resisting further soil compaction.