Prediction and field measurements of tillage tool draft forces and efficiency in cohesive soils

Field experiments were conducted in clay and sandy clay loam soils using flat tillage blades of varying width, depth and rake angle. Measured quantities of draft force and disturbed soil areas for the different test conditions were compared to those predicted by a model of soil wedge failure in front of narrow blades, with reasonable agreement. Both the specific draft force per unit soil area and the degree of soil loosening were observed to increase with the relative narrowness of the tillage blades and with the rake angle, as predicted by the model.     

New wings on the interaction between conventional subsoiler and paraplow tines with the soil: effects on the draft and the properties of soil

Equipping tines with the wings increases draft and soil loosening. Wing angles affect tine performance, soil aggregation and remained residue. In this research, conventional wing with no bent plus backward and forward bent wings with bend angles of 10 and 20° were attached to both a subsoiler and paraplow tine. The rake angle of all wings was 15°. The effects of tine and wing on draft, soil disturbance area, specific draft, remained residue, and mean weight diameter (MWD) were investigated in a clay loam soil at depth of 40 cm and speed of 1.6 km h^?1. The effect of tine and wing plus interaction of them on all parameters was significant (p < 0.01) with the exception of remained residue. The bent-winged tines required higher draft and caused higher disturbance area, lower specific draft, and lower MWD than the conventional tines and those without wing. The highest draft, disturbed area and remained residue plus the lowest specific draft and MWD were obtained when applying the 10° forward bent-winged tines. In present work, the paraplow equipped with forward bent wings with a bend angle of 10° was suggested as a suitable tool for deep soil loosening under a conservation tillage system.     

Effects of rake angle of chisel plough on soil cutting factors and power requirements: A computer simulation

A computer simulation was conducted to predict the effects of rake angle of a chisel plough and soil bulk density on angle of soil failure plane, rupture distance, width of side crescent, frictional, overburden, cohesion and adhesion soil cutting factors, draft forces and drawbar power requirements. The experimental work was carried out in two locations. Soil of the first location was sandy clay with the soil bulk densities of 1.75 and 1.70 g/cm³ for firm and loose soil conditions, respectively, with an angle of internal friction of 30° and a surface friction angle of 20°, cohesion of 2.5 kN/m² and adhesion of 1.2 kN/m². Soil of the second location was clay loam with the soil bulk densities of 1.65 and 1.50 g/cm³ for firm and loose soil conditions, respectively, with an angle of internal friction of 34° and a surface friction angle of 23°, cohesion of 2.4 kN/m² and adhesion of 1.14 kN/m². The prediction showed that the angle of failure plane found to decrease with the rake angle. The rupture distance decreased with the rake angle from 15° to 55° and then increased as the rake angle increased over 55°. The width of the side crescent increased as the rake angle increased and the maximum value and the minimum value were recorded at 75° and at 15°. Values of frictional and overburden factors decreased as rake angle increased. The maximum and minimum values were recorded at 15° and 75°, respectively. The values of cohesion factor increased as rake angle increased. The maximum value was recorded at rake angle of 75° and the minimum value was recorded at rake angle of 15°. Adhesion factor was found to change inversely with the rake angle from 15° to 55° and then to change directly with the rake angle over 55°. The draft force decreased with the rake angle and reached its minimum value at 45° rake angle. Over 45°, the draft force increased and reached its maximum value at 75° rake angle. The draft increased with soil bulk density. The power required for moving the plough recorded the maximum value at rake angle of 15°, while the minimum value was recorded at 55° rake angle. The values of power increased with decrease of soil bulk density. The predicted values demonstrated some deviations from the experimental values of the draft force and the drawbar power.     

A nonlinear 3D finite element analysis of the soil forces acting on a disk plow

This study aimed to compare predicted soil forces on a disk plow with measured forces within the tillage depth of clay (90 g kg⁻¹ sand, 210 g kg⁻¹ silt, 700 g kg⁻¹ clay) and sandy loam (770 g kg⁻¹ sand, 40 g kg⁻¹ silt, 190 g kg⁻¹ clay) soils. The model assumed the effects of both tilt angle and plowing speed. Two plowing speeds (4 and 10 km/h) at three tilt angles (15°, 20° and 25°) were compared and the draft, vertical, and side forces determined. A 3D nonlinear finite element model was used to predict the soil forces while a dynamometer was used to measure them on a disk plow in the field. An incremental method was used to deal with material nonlinearity and the Trapezoidal rule method was used to analyze the dynamic response of soil during tillage. Field tillage experiments were conducted to verify the results of the finite element model. It was found that increasing the tilt angle of the plow increased the draft and vertical forces and decreased the side force. Increasing plowing speed increased the draft and side forces and decreased the vertical force. Generally, the results from the finite element model were found to be compatible with the experimental results in clay soil, while in sandy loam the differences between predicted and measured data were probably due to problems of measuring soil mechanical characteristics in the triaxial test.     

SW—Soil and Water: Improvement of Whitish Oasis Soil, Part 1: Field Experiments with a Four-stage Subsoil Mixing Plough

A prototype four-stage subsoil mixing plough was designed in Japan and built in China for the improvement of whitish oasis soil. The machine was transported to two places in China for field tests where the whitish oasis soil is found. This paper presents the trash mixing rate into mixed layer of Bca and C horizons, the inverting rate of the Bca and C horizons and the draught of the plough in the whitish oasis soil.The results show that the rolling resistance of the tracked vehicle (T802), on which the plough was mounted, was about 8 kN and the draught of the first plough body which tilled the Ap horizon was about 4 kN with a working depth of 200 mm and a working width of 500 mm. The draught of the second plough body, which tilled the surface of the Ap horizon, was about 2 kN with a working depth of 50 mm. The draught of the third plough body increased steeply with greater working depths. The draughts were about 8, 14 and 24 kN, respectively, for working depths of 117, 239 and 300 mm. The draught of the fourth plough body also increased steeply with greater working depth. The draughts were about 7, 14 and 18 kN, respectively, for working depths of 117, 178 and 239 mm. When the whitish oasis soil was disturbed by the plough bodies, it was observed that the whitish oasis soil was very hard but comparatively brittle and easily broken up. This property explains the smaller draught requirements in the whitish oasis soil despite a greater soil strength. The values of the soil-inverting rate ranged between 0·45 and 0·6, and the average value was 0·5. Perfect inversion of the Bca and C horizons was not possible, but good mixing was achieved by the plough. The average trash mixing rate in Inner Mongolia was 0·85, and that in North of River was 0·95. These data show that even in Inner Mongolia where the trash material is long, a fairly uniform trash mixing was possible.     

Effect of the number of tractor passes on soil rut depth and compaction in two tillage regimes

The initially high level of soil compaction in some direct sowing systems might suggest that the impact of subsequent traffic would be minimal, but data have not been consistent. In the other hand on freshly tilled soils, traffic causes significant increments in soil compaction. The aim of this paper was to quantify the interaction of the soil cone index and rut depth induced by traffic of two different weight tractors in two tillage regimes: (a) soil with 10 years under direct sowing system and (b) soil historically worked in conventional tillage system. Treatments included five different traffic frequencies (0, 1, 3, 5 and 10 passes repeatedly on the same track). The work was performed in the South of the Rolling Pampa region, Buenos Aires State, Argentina at 34°55′S, 57°57′W. Variables measured were (1) cone index in the 0–600 mm depth profile and (2) rut depth. Tyre sizes and rut depth/tyre width ratio are particularly important respect to compaction produced in the soil for different number of passes. Until five passes of tractor (2WD), ground pressure is responsible of the topsoil compaction. Until five passes the tyre with low rut depth/tyre width ratio reduced topsoil compaction. Finally, the farmer should pay attention to the axle load, the tyre size and the soil water content at the traffic moment.     

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.     

Characterization of soil physical properties and organic matter under long-term primary tillage in a humid climate

Chisel ploughing is considered to be a potential conservation tillage method to replace mouldboard ploughing for annual crops in the cool-humid climate of eastern Canada. To assess possible changes in some soil physical and biological properties due to differences in annual primary tillage, a study was conducted for 9 years in Prince Edward Island on a Tignish loam, a well-drained Podzoluvisol, to characterize several mouldboard and chisel ploughing systems (at 25 cm), under conditions of similar crop productivity. The influence of primary tillage on the degree of soil loosening, soil permeability, and both organic matter distribution throughout the soil profile and organic matter content in soil particle size fractions was determined. At the time of tillage, chisel ploughing provided a coarser soil macrostructure than mouldboard ploughing. Mouldboard ploughing increased soil loosening at the lower depth of the tillage zone compared to chisel ploughing. These transient differences between primary tillage treatments had little effect on overall soil profile permeability and hydraulic properties of the tilled/non-tilled interface at the 15–30 cm soil depth. Although soil microbial biomass, on a volume basis, was increased by 30% at the 0–10 cm soil depth under chisel ploughing, no differences were evident between tillage systems over the total tillage depth. Mouldboard ploughing increased total orgainc carbon by 43% at the 20–30 cm soil depth, and the carbon and nitrogen in the organic matter fraction ≤ 53 μm by 18–44% at the 10–30 cm soil depth, compared to chisel ploughing.     

Infiltration patterns into two soils under conventional and conservation tillage: influence of the spatial distribution of plant root structures and soil animal activity

The characteristics and properties of the soil macropore system may cause different infiltration behavior under different tillage practices. To evaluate the effect of a specific tillage system on infiltration and percolation with particular regard to the influence of crop structure and soil animal activity dye tracer irrigation experiments were conducted in a silty (Luvisol) as well as in a sandy loam soil (Podzolluvisol). The spatial distribution of water flow paths was experimentally examined at four square areas of 0.49 m², under conservation and conventional tillage. Natural rainstorms were simulated by irrigating the plots with 2.8×10⁻³ M methylene blue solutions. For both soils the root crowns of the agricultural crop, wormcasts and stained soil sections as well as macroscopic conduits were traced on plastic sheets. The investigated soil depths were 0, 5, 10 and 20 cm for the both soils. For the Luvisol, the 30, 40, 50, 80 and 120 cm depths were also studied.For the Luvisol, the conservation tillage plot revealed pronounced vertical connectivity and continuity of the macropore network (maximum depth of stained pores=120 cm), while at the conventional tillage plot, continuous macropores were observed to soil depths of 50 cm, but mainly restricted to the ploughed topsoil (0–30 cm soil depth).For the Podzolluvisol, at the conservation tillage site extensive mulch residues prevented water transport beneath 5 cm soil depth. In contrast, at the conventionally tilled site stained water reached a depth of 20 cm. For all investigated plots on both soil types, the location of the root crowns of agricultural crop and of wormcasts was not related to percolation patterns.The results suggest that conservation tillage on silty soils under agricultural landuse could induce an increased water retention capacity reducing the significance of fast runoff components.     

An approach for draft prediction of combination tillage implements in sandy clay loam soil

A methodology to predict the draft requirements of combination tillage implements in any soil and operating conditions was developed. This methodology required the draft requirements of individual tillage implements in undisturbed soil condition and draft utilization ratio of the rear passive set of combination tillage implement, which is defined as the ratio of the drafts of the rear passive set operating in combination and individually. Laboratory experiments were conducted to measure the draft requirements of a reference tillage tool (single disk), three scale-model individual (moldboard plow, cultivator and disk gang) and two combination (moldboard plow with disk gang and cultivator with disk gang) tillage implements at different depths (5, 7.5 and 10 cm), speeds (1.2, 2.2, 3.2 and 4.2 km/h), wet bulk densities (in the range of 1.27–1.85 g/cm³) and cone index penetration resistance values (in the range of 445–1450 kPa) in soil bin filled with sandy clay loam soil. The average draft utilization ratio of the reference tillage tool obtained were analyzed by both orthogonal and multiple regression techniques to develop the regression equation considering soil properties, operating and tool parameters. The developed draft equation based on the above mentioned methodology was verified with the data obtained for the draft of scale-model and prototype combination tillage implements in the laboratory and field conditions, respectively. It was found that the developed equation predicted the draft of both combination tillage implements within an average absolute variation of 18.0 and 13.5%, respectively.     

Simulation of soil–blade interaction for sandy soil using advanced 3D finite element analysis

In this paper a finite element investigation of the tillage of dry sandy soil, using the hypoplastic constitutive material model, is described. In most earth moving machinery, such as bulldozers or tillage tools, the working tool is a blade. Hence for tillage systems, accurately predicting the forces acting on the blade is of prime importance in helping to enhance productivity. The initial conditions, such as blade geometry or soil type, and operating conditions, such as cutting speed and cutting depth, have been shown experimentally to have a great effect on machine productivity. Experimental studies give valuable insights but can be expensive and may be limited to certain cutting speeds and depths. Results are also highly dependent on the accuracy of the measuring devices. However with increasing computational power and the development of more sophisticated material models, finite element analysis shows more promise in analyzing the factors affecting soil–blade interaction. Most of the available finite element studies in the literature are two-dimensional or if three-dimensional (3D), are limited to a certain blade displacement depending on the element distortion limit before the solution has convergence problems. In this study, a 3D finite element analysis of soil–blade interaction was carried out based on predefined horizontal and vertical failure surfaces, to investigate the behavior of the soil–blade interface and study the effect of blade-cutting width and lateral boundary width on predicted forces. Sandy soil was considered in this study and modeled using the hypoplastic constitutive model implemented in a commercial finite code, ‘ABAQUS’. Results reveal the validity of the concept of predefined failure surfaces in simulating soil–blade interaction and the significant effect of blade-cutting width, lateral boundary width and soil swelling on cutting forces.     

Spatial Heterogeneity of Soil C:N Ratio in a Mollisol Watershed of Northeast China

The spatial variability of the soil C:N ratio (C:N) influences C and N leaching and basic fertility in the field. This paper aims to identify the spatial heterogeneity of C:N in a Mollisol watershed of Northeast China and determine the main mechanisms that drive these differences. A random sampling method was used, with both geostatistical and traditional analysis being used to describe the spatial distribution of the C:N at various depths. C:N was also compared between slope position, previous vegetation and tillage methods in the watershed. The horizontal distribution of the C:N was mainly influenced by structural factors (88·4–99·9%) and often gradually deceased along the hydrographic flow direction, becoming lowest at the watershed outlet. The C:N increased as soil depth increased at all slope positions, and was higher on the back slope than on summit slope, followed by bottom slope in all soil depths. C:N was negatively (significant at p < 0·01) correlated to TN, and positively (significant at p < 0·05) correlated to elevation at all soil depths. Compared to the reforested area, C:N was typically greater in the agricultural area in the 20–60 cm depth. The planting of soybean (Glycine max L) can significantly increase the C:N at the 40–50 cm depth. C:N was higher in cross‐slope tillage than in down‐slope tillage, especially at soil depths of 40–50 cm. Generally, topographical factors, land use, crop planting and tillage methods can effectively influence the spatial heterogeneity of C:N in this watershed. Copyright © 2015 John Wiley & Sons, Ltd.     

Soil compaction produced by tractor with radial and cross-ply tyres in two tillage regimes

The aim of this paper was to quantify soil compaction induced by tractor traffic on two tillage regimes: conventional tillage and direct drilling. Traffic was simulated with one pass of a conventional 2WD tractor, using four configurations of cross-ply rear tyres: 18.4–34, 23.1–30, 18.4–38 and 24.5–32, and four configurations of radial tyres 18.4R34, 23.1R 30, 18.4R 38 and 24.5R 32, with two ballast conditions used in each configuration. The experiment was conducted in the east of the Rolling Pampa region, Buenos Aires State, Argentina at 34°25′S, 59°15′W; altitude 22 m above sea level. Rut depth after traffic and soil bulk density and cone index in a 0–450-mm profile were measured before and after traffic. Considering topsoil level, in two tillage regimes, all treatments induced significant values of soil compaction as compared to the control plot without traffic. Subsoil compaction increased as total axle load increased and was independent of ground pressure. For the same tyre configuration, radial tyre caused less soil compaction than the cross-ply.     

Root growth conditions in the topsoil as affected by tillage intensity

Many studies have reported impeded root growth in topsoil under reduced tillage or direct drilling, but few have quantified the effects on the least limiting water range for root growth. This study explored the effects of tillage intensity on critical soil physical conditions for root growth in the topsoil. Samples were taken from a 7-year tillage experiment on a Danish sandy loam at Foulum, Denmark (56°30′ N, 9°35′ E) in 2008. The main crop was spring barley followed by either dyer's woad (Isatis tinctoria L.) or fodder radish (Raphanus sativus L.) cover crops as subtreatment. The tillage treatments were direct drilling (D), harrowing 8-10 cm (H), and ploughing (P) to 20 cm depth. A chisel coulter drill was used in the H and D treatments and a traditional seed drill in the P treatment. Undisturbed soil cores were collected in November 2008 at soil field moisture capacity from the 4-8 and 12-16 cm depths.We estimated the critical aeration limit from either 10% air-filled porosity (ε_a) or relative gas diffusivity (D/D₀) of 0.005 or 0.02 and found a difference between the two methods. The critical limit of soil aeration was best assessed by measuring gas diffusivity directly. Root growth was limited by a high penetration resistance in the D and H soils (below tillage depth). Poor soil aeration did not appear to be a significant limiting factor for root growth for this sandy loam soil, irrespective of tillage treatment. The soil had a high macroporosity and D/D₀ exceeded 0.02 at field capacity. Fodder radish resulted in more macropores, higher gas diffusivity and lower pore tortuosity compared to dyer's woad. This was especially important for the H treatment where compaction was a significant problem at the lower depths of the arable layer (10-20 cm depth). Our results suggest that fodder radish could be a promising tool in the amelioration of soil compaction.     

Optimum energy model for tillage

An optimum energy model has been given, for a soil—tool system where the soil is non-uniform, and the tool width, depth of cut, tilt angle, approach angle and forward velocity vary. The objective function of the energy model is based upon a force prediction equation, which necessitates quantification of analog values using a distorted model of the tillage tool whose performance is to be evaluated.     

深松深度对砂姜黑土耕层特性、作物产量和水分利用效率的影响

研究深松深度对砂姜黑土耕层特性、作物产量和水分利用效率的影响,可为构建砂姜黑土合理耕层的耕作深度指标提供依据。本研究基于多年定位大田试验,采用大区对比设计,设置4个深松深度(30 cm、40 cm、50 cm、60 cm)处理,以旋耕(RT,平均耕作深度为15 cm)作为对照,研究不同深松深度对土壤紧实度、土壤三相比(R)值、作物根系形态、作物产量和水分利用效率的影响。研究结果表明,深松深度增加能显著降低土壤紧实度,使土壤的三相比(R)更加合理,进而促进作物根系生长。不同深松深度中,深松60 cm处理的土壤紧实度和三相比(R)值与对照相比降幅最大,深松40 cm处理的冬小麦根系生物量最大,深松50 cm处理的夏玉米根系生物量最大。深松不仅增加作物产量,还提高作物水分利用效率。深松30 cm处理的周年作物产量最高,比对照增产12.2%,但与深松40 cm处理差异不显著。深松50 cm处理的周年水分利用效率最高,但与深松30 cm和深松40 cm处理差异不显著。深松30 cm、40 cm和50 cm的周年水分利用效率比对照分别增加9.1%、8.8%和12.7%。因此,砂姜黑土适宜的深松深度为30~40 cm。     

Tillage choices affect biochemical properties in the soil profile

Intensive conventional farming and continuous use of land resources can lead to agro-ecosystem decline and increased releases of CO₂ to the atmosphere as soil organic matter (OM) decays. The aim of this research was to evaluate the influence of varying types and depths of tillage on microbial biomass, C content, and humification in the profile of a loamy-sandy soil in the Mugello valley, close to the Apennine Mountains, in Italy. Soil samples were collected to depths of 0–10, 10–20, 20–30 and 30–40 cm, in the ninth year following introduction of tillage practices. Highest content of all C forms examined (total, extractable and humified) was found at the 0–10 cm depth with minimum tillage (MT) and ripper subsoiling (RS) and at the 30–40 cm depth with conventional tillage (CT). Humified C decreased with depth in soils under MT and RS. None of the tillage systems showed any difference in total N and microbial biomass C in the upper depths, but concentrations were greater below 20 cm in soils subjected to CT, than other tillage systems. Crop production was similar in all tillage systems. Stratification and redistribution of nutrients were consistent with the well known effects of tillage reduction. Total organic C and its distribution in the profile depended on the tillage system employed. MT and RS can be regarded as excellent conservation tillage systems, because they also sequester C.     

Effect of planting date and tillage system on soybean root growth

Soil erosion and moisture retention are major concerns of soybean growers. Conservation tillage provides residue cover to reduce soil loss and water evaporation. This study was conducted on a Tiptonville silt loam near Portageville, MO, USA. to determine the effect of tillage system and planting date on soybean [Glycine max (L.) Merrill] root growth and distribution. Tillage systems were conventional (clean) tillage, ridge tillage, and no‐tillage. ‘Essex’ soybean was planted on 14 May, 15 June, and 7 July in 1992 and 12 May, 2 June, and 21 June in 1993. Roots were observed 30 and 60 days after emergence (DAE) using a minirhizotron system. Stand density was not affected by tillage in either year or by planting date in 1992. Tillage did not effect rooting depth in either year. In 1992, rooting depth 30 DAE was greater for the 14 May planting date than for either of the other two planting dates. No other planting date effects on rooting depth were found. Among soil depths, root length density (RLD) was greatest for the 14 to 26 cm depth in 1992 and for the 0 to 13 cm depth in 1993. Neither tillage system nor planting date affected RLD in either year and there was no interaction between these main effects and soil depths. The largest changes in RLD (CRLD) were observed in the 14 to 26 cm and 27 to 39 cm depths in 1992 and the 0 to 13 cm depth in 1993. Tillage did not planting date in 1992 and the 12 May and 2 June planting dates in 1993 produced the highest yields. Tillage did not affect yield and there was no interaction between tillage and planting date.     

Soil loosening on permanent raised-beds in arid northwest China

Poor lateral water infiltration into permanently raised beds (PRB) can reduce crop yield and water use efficiency (WUE) in dryland agriculture. Especially for densely planted crops the reduced soil moisture affects seedling emergence and causes slow crop growth. Soil loosening with three different types of cutters was tested to overcome this problem of wide PRB in this study. A field experiment with five treatments (traditional tillage, bed without soil loosening, bed with soil loosening by two-edge cutter, bed with soil loosening by flat cutter and bed with soil loosening by V-shaped cutter) was conducted in the Hexi Corridor, northwest China, on spring wheat in 2005 and 2006. The effects of soil loosening and the performances of the three cutters were assessed based on 2 years of soil moisture, bulk density, temperature, spring wheat growth, yield, WUE, power and fuel consumption data. Soil loosening significantly increased lateral water infiltration and thus improved soil water content by 3–8% to 100 cm depth and soil temperature by 0.2–0.4 °C to 30 cm depth compared to beds without soil loosening on sandy-loam soil in 100 cm wide bed systems. Furthermore, bulk density at 10–20 cm depth was about 7.4% lower for bed with soil loosening treatments than for bed without soil loosening. The best results were achieved by the V-shaped cutter, which at a slight additional fuel consumption of 0.46–0.84 l ha⁻¹ offered the greatest benefits to spring wheat yield and WUE. Spring wheat yields increased by 5% and WUE improved by 38% compared to traditional tillage due to higher soil moisture and temperature, lower bulk density and faster growth. The improvements in WUE have tremendous implications in the arid areas of northwest China where agriculture relies heavily on irrigation, but water resources are scarce. We conclude therefore that soil loosening by V-shaped cutter is an efficient way to remove poor water infiltration, and significantly improve yield and WUE for wide beds under PRB farming system in arid areas of northwest China.     

Seedbed compaction produced by traffic on four tillage regimes in the rolling Pampas of Argentina

The main function of primary tillage is to increase the soil's structural macro-porosity, but during secondary tillage operations over these freshly tilled soils, traffic causes significant soil compaction. In terms of soil conservation however, there is evidence that direct sowing is a more sustainable system, even though there is still insufficient information about the rheology of a non-tilled soil under traffic. The objective of this study was to compare the traffic intensity and soil compaction caused by four different tillage regimes currently used by Argentinean farmers (1 direct sowing with a tractor and planter weighing 127 kN and 3 conventional tillage systems with equipment weighing 55.2 kN). The work was performed in the east of the Rolling Pampa region, Buenos Aires State, Argentina at 34°25′S, 59°15′W. Variables measured were: (1) cone index in the 0–450 mm depth profile; (2) bulk density; (3) total soil porosity; and (4) rut depth. (a) Results indicated that in the depth range 0–150 mm with all tillage treatments, bulk density and cone index values generated by tractor traffic were greater than the 1.3 Mg m⁻³ and 1400 kPa respectively. Similarly in deeper layers these parameters were greater than 1.45 Mg m⁻³ and 2000 kPa respectively. Measurements revealed that traffic reduced topsoil porosity under direct sowing by an average of 7% and under conventional tillage by 7.6–14.8% confirming that both systems cause both topsoil and subsoil compaction.