Overview of Current Research Situations of Subsoiler

Modern subsoiling technology is a little ploughing measure in dry land protective farming technology system.The subsoiler can scarify soil,deepen the arable layer,break the plough layer,improve the soil permeability,increase soil infiltration speed and amount,and create an arable layer structure with coexistence of fictional and real situation.Also,it can effectively promote development and growth of crop root system and play a favorable role in drought resistance and yield increase of crops.This paper made a simple overview of the subsoiling technology,current development situation of subsoiler both at home and abroad,and classification of subsoilers.

Distinct element method analysis and field experiment of soil resistance applied on the subsoiler

Since the design of the subsoiler is a complex work,the interaction between the subsoiler and soil was investigated by using Distinct Element Method(DEM)in this study.Based on the traditional discrete element theory,the 3D model of soil particles and the subsoiler were established after considering the liquid bridge force between soil particles.The operating resistance curves of the subsoiler were achieved after the DEM simulation at a speed of 1 m/s,and three depths of 180 mm,220 mm and 260 mm,respectively.The simulation curves agreed well with the field experimental results based on relative errors of 2.96%,14.95%and 7.15%,respectively,at three depths.All these data proved that it was feasible and favorable to analyze the performance of the subsoiler by using the DEM and it is of important significance for studying and further optimizing the structure of the subsoiler.

Determination of the draft force for different subsoiler points using discrete element method

Generally,a subsoiler is comprised of a shank and a point.The point shape has a significant effect on the draft force of a subsoiler.In this study,the draft force of subsoilers with four different points were compared under the speed of 0.8 m/s and the depth of 350 mm in the soil bin.Discrete Element Method(DEM)was applied in simulating the working process of the subsoiler.The stiffness of soil particles used in DEM was calibrated by comparing the simulated draft force of a standard arc-shaped subsoiler with the experiment.The calibrated soil particle stiffness was 1.1×104 N/m.The validated model was then used to compare the draft force of subsoilers with four different points under the same condition in the test.Results showed that different points would cause different draft forces.The subsoiler with short chisel point caused the smallest draft force(2885 N)while the point with short face and wings had the largest force(4474 N).The relative errors of the simulated results were less than 4%,which proved that DEM was an effective way for predicting the draft force of subsilers.The velocity field and contact force filed could show the movement of soil around the subsoiler.

Design and experiment of a bionic vibratory subsoiler for banana fields in southern China

Subsoiling is essential in the tillage of banana planting,as banana plants have a fairly sturdy pseudostem and wide row spacing while soil tends to be compacted.In this study,a bionic vibrating subsoiler for banana fields was developed,verified,and evaluated.The vibrator was designed based on crank-rocker mechanism while the bionics design was used for subsoiler development.The forces on the susboiler were analyzed to verify the strength of the subsoiler tine.To test the performance of the subsoiler,field tests were conducted to measure the draft force and fuel consumption.There was approximately 14%reduction in the draft force and 22%increase in the fuel consumption in vibrating mode compared with that in non-vibrating mode.In conclusion,the study results could be applied in China’s tropical agricultural regions.

Discrete element simulations and experiments of soil-winged subsoiler interaction

Understanding soil disturbance behaviors under the impact of the winged subsoiler is critical for designing or optimizing the winged subsoiler(a primary subsoiling tool).In this study,a soil-winged subsoiler interaction model was developed and the effects of winged subsoiler on soil disturbance behaviors were investigated using the discrete element method(DEM)simulations and lab soil-bin tests.The results showed that wings mainly affected the disturbance range and fragmentation degree of soil above them.The draught forces of share section(SS),arc section in the hardpan(ASHP),arc section in the top layer(ASTL)and line section(LS)were accounted for 69.53%,25.22%,4.73%and 0.52%of the total draught force of winged subsoiler;the lateral disturbance range from high to low of the soil at different depths followed the ranking:top layer(TL),hardpan disturbed by arc section(HDAS)and hardpan disturbed by share section(HDSS).Wings had the greatest influence on the draught force of ASHP.Adding wings to an arc-shaped subsoiler increased the disturbance areas of HDAS,TL and HDSS by 47.52%,7.74%and 4.59%,respectively,but meanwhile increased the total draught force by 36%.Compared with a non-winged subsoiler,winged subsoiler had higher soil looseness(15.83%),soil disturbance coefficient(58.59%),furrow width(448.65 mm)and soil disturbance area ratio(0.3835),but poorer soil surface flatness(19.79 mm)and lower soil loosening efficiency(39.35 mm²/N).This study provided critical information for optimizing winged subsoilers on aspects of improving soil loosening effectiveness and reducing draught force.

Optimized design and field experiment of a staggered vibrating subsoiler for conservation tillage

Soil compaction is a common problem facing conservation fields that restricts crop root growth and causes yield decrease.Subsoil techniques have been developed to break up the compaction layer.However,subsoil implement requires large draft power that hampered the development of subsoil techniques for most of developing countries due to lack of large scale tractors.Aiming to optimize the penetration resistance of the subsoiler and create a good working environment for the operators,a staggered vibrating subsoiler was developed.A new staggered vibrating mechanism was designed to generate the staggered vibration of the shanks meanwhile the V-shape shanks arrangement was adopted to keep relative balance for the subsoiler.In order to obtain optimum working parameters of the vibration frequency and forward speed,the trajectory of shanks was simulated by using the MATLAB software.The forward speed of 2-3 km/h with vibration frequency of 12 Hz was recommended to acquire an effective decrease in draft force.Field performance of this subsoiler was evaluated in terms of the draft force,power requirement and tractor wheel slippage.By comparing the two operation modes,staggered vibrating(SV)and rigid(NV)of shanks,the decrease ratios of draft force for SV were determined by 16.97%,12.12%and 9.02%at forward speeds of 2.2 km/h,2.6 km/h and 3.1 km/h,respectively.This is better than the research for the 1SZ-460 vibratory subsoiler that was decreased by 9.09%in draft force.The power requirement for SV was not significantly greater than that for NV.The obviously decreased wheel slippage was observed for SV by decrease of 12.47%,17.96%and 21.79%at forward speeds of 2.2 km/h,2.6 km/h and 3.1 km/h,respectively.In conclusion,the staggered vibrating subsoiler presents preferable working performance and is recommended to be applied in subsoil tillage process for developing countries.

Simulation and experimental study on drag reduction and anti-adhesion of subsoiler with bionic surface

A new subsoiler with placoid scale microstructure bionic surface was proposed which mimicked shark skin to reduce tillage resistance and soil adhesion during subsoiling cultivation.The contour curves of placoid scale microstructure on shark skin were fitted,and two kinds of bionic subsoiler with continuous and discontinuous microstructures were designed and fabricated,respectively.The effects of different bionic surfaces on tillage resistance were investigated by finite element simulation and experiment.The results indicated that the bionic subsoiler with discontinuous microstructure reduced the horizontal and vertical force by 21.3%and 24.8%,respectively.The subsoiler with discontinuous microstructure surface can prevent the adhesion between the soil and subsoiler surface more efficiently.

Tillage force and disturbance characteristics of different geometric-shaped subsoilers via DEM

With the increased use of agricultural machinery in field operations,soil compaction has become increasingly severe,and the plough pan has become deeper.Subsoiling is an excellent way to address this problem.However,it is limited by high energy consumption,which is closely related to tillage force.To investigate the effect of the geometric shape of shanks and tines on tillage force and soil disturbance in loam,a layered soil model in accordance with the actual conditions was established and five different subsoilers were simulated via discrete element modeling.The results indicated that the shank impacted soil disturbance and tine impacted tillage force.The draft force of curved shank and chisel tine was 8%less than that of the straight shank and sweep tine.The straight shank and sweep tine produced a larger furrow profile and a higher furrow width.The subsoiler with curved shank and chisel tine(C-C)exhibited the lowest specific resistance(12.87,17.52,19.46 and 21.18 kN/m^2 in the 30,35,40 and 45 cm tillage depth,respectively)considering the draft force and soil disturbance characteristics.Hence,these results will facilitate in the selection of a suitable subsoiler and design of new subsoilers with lower energy consumption requirements for loam areas worldwide.

Design and experiment of anti-vibrating and anti-wrapping rotary components for subsoiler cum rotary tiller

The commonly used subsoiling cum rotary tiller machine(SRT)in Northern China is a combination of subsoiler and horizontal rotary tiller,however backfilling of the subsoiling slot,excessive vibration and plant residue wrapping on rotary components has been rarely considered.Therefore,the rotary components and assembly were redesigned to address these issues and to an SRT fitted with IT225 short curve rotary blades behind the V-shape subsoiling slots and IIT245 long curve rotary blades between the tines.Long and short blades were fitted on a rotor in a double helix,with optimal spiral angles of 65° and 90°,and phase angle of 147°and 180°,respectively.Compared with the commonly used SRT(CSRT),the additional anti-wrapping cutting blades in the circumferential and axial direction of ASRT could remove hanging residue on the blade holders,wrapping on the rotor and formation of an isolation layer.Moreover,the cutting edge curve of anti-wrapping cutting blades was an exponential curve.Field tests demonstrated that the redesigned SRT with anti-vibrating and anti-wrapping rotary components(ASRT)had was a significant advancement over the CSRT.Moreover,the working depth of rotary tillage was more stable,while other observations confirmed that backfilling of the subsoiling slot was also improved.

Effect of subsoil tillage depth on nutrient accumulation, root distribution, and grain yield in spring maize

A four-year field experiment was conducted to investigate the effect of subsoiling depth on root morphology, nitrogen(N), phosphorus(P), and potassium(K) uptake, and grain yield of spring maize. The results indicated that subsoil tillage promoted root development,increased nutrient accumulation, and increased yield. Compared with conventional soil management(CK), root length, root surface area, and root dry weight at 0–80 cm soil depth under subsoil tillage to 30 cm(T1) and subsoil tillage to 50 cm(T2) were significantly increased, especially the proportions of roots in deeper soil. Root length, surface area, and dry weight differed significantly among three treatments in the order of T2 > T1 > CK at the12-leaf and early filling stages. The range of variation of root diameter in different soil layers in T2 treatment was the smallest, suggesting that roots were more likely to grow downwards with deeper subsoil tillage in soil. The accumulation of N, P, and K in subsoil tillage treatment was significantly increased, but the proportions of kernel and straw were different. In a comparison of T1 with T2, the grain accumulated more N and P, while K accumulation in kernel and straw varied in different years. Grain yield and biomass were increased by 12.8% and 14.6% on average in subsoil tillage treatments compared to conventional soil treatment. Although no significant differences between different subsoil tillage depths were observed for nutrient accumulation and grain yield, lodging resistance of plants was significantly improved in subsoil tillage to 50 cm, a characteristic that favors a high and stable yield under extreme environments.

Effects of Subsoiling on Soil Moisture Under No-Tillage for Two Years

In order to improve the water use efficiency under conservation tillage, the effects of subsoiling on soil moisture under notillage were studied. An experiment of 40 cm subsoiling in a field kept under no-tillage for 2 years was operated from 2005 to 2006. Based on the data of the soil moisture and crop yield, the physical basis of subsoiling for water conservation and yield increase was analyzed. The results showed that the soil water storage under subsoiling, from the soil surface to a depth of 100 cm was more than that under no-tillage for the growth season. In the 0-100 cm soil depth, the soil moisture in 50-100 cm depth under subsoiling was more compared with no-tillage, which increased when it＇s drought and decreased when it＇s rainy with the increase in soil depth. Compared with no-tillage, subsoiling could reduce the water consumption of oats in the 0-50 cm depth and increase the water consumption in the 50-100 cm depth. Also, subsoiling increased the yield by 18.29% and the water use efficiency by 16.8% in a two-year average. The effects of subsoiling on water conservation and yield increase were affected by precipitation, and a well-proportioned rainfall was better to increase yield and water use efficiency. Meanwhile, subsoiling decreased bulk density, which increased with the available precipitation. Subsoiling under no-tillage is the effective rotation tillage to contain more soil moisture and improve water use efficiency in ecotone of North China.

Subsoiling and Ridge Tillage Alleviate the High Temperature Stress in Spring Maize in the North China Plain

High temperature stress（HTS） on spring maize（Zea mays L.） during the filling stage is the key factor that limits the yield increase in the North China Plain（NCP）.Subsoiling（SS） and ridge tillage（R） were introduced to enhance the ability of spring maize to resist HTS during the filling stage.The field experiments were conducted during the 2011 and 2012 maize growing seasons at Wuqiao County,Hebei Province,China.Compared with rotary tillage（RT）,the net photosynthetic rate,stomatal conductance,transpiration rate,and chlorophyll relative content（SPAD） of maize leaves was increased by 40.0,42.6,12.8,and 29.7% under SS,and increased by 20.4,20.0,5.4,and 14.2% under R,repectively.However,the treatments reduce the intercellular CO 2 concentration under HTS.The SS and R treatments increased the relative water content（RWC） by 11.9 and 6.2%,and the water use efficiency（WUE） by 24.3 and 14.3%,respectively,compared with RT.The SS treatment increased the root length density and soil moisture in the 0-80 cm soil profile,whereas the R treatment increased the root length density and soil moisture in the 0-40 cm soil profile compared with the RT treatment.Compared with 2011,the number of days with temperatures 33°C was more 2 d and the mean day temperature was higher 0.9°C than that in 2012,whereas the plant yield decreased by 2.5,8.5 and 10.9%,the net photosynthetic rate reduced by 7.5,10.5 and 18.0%,the RWC reduced by 3.9,5.6 and 6.2%,and the WUE at leaf level reduced by 1.8,5.2 and 13.1% in the SS,R and RT treatments,respectively.Both the root length density and the soil moisture also decreased at different levels.The yield,photosynthetic rate,plant water status,root length density,and soil moisture under the SS and R treatments declined less than that under the RT treatment.The results indicated that SS and R can enhance the HTS resistance of spring maize during the filling stage,and led to higher yield by directly improving soil moisture and root growth and indirectly improving plant water status,photosynthesis and grain filling.The study can provide a theoretical basis for improving yield of maize by adjusting soil tillage in the NCP.

Effects of subsoiling depth,period interval and combined tillage practice on soil properties and yield in the Huang-Huai-Hai Plain,China

Compact!on layers are widely distributed in the Huang-Huai-Hai Plain,China,which restrict root growth and reduce yields.The adoption of subsoiling has been recommended to disrupt compacted soil layers and create a reasonable soil structure for crop development.In this paper,the effects of subsoiling depth(30,35 and 40 cm),period interval(2 or 3 years)and combined pre-sowing tillage practice(rotary cultivation or ploughing)on soil condition improvement was studied on a tidal soil in the Huang-Huai-Hai Plain.Seve n tillage patter ns were desig ned by combini ng differe nt subsoili ng depths,period intervals and pre-sowing.The evaluation indicators for soil condition improvement were as follows:thickness of the plough layer and hard pan,soil bulk density,cone index,soil three-phase R values,alkali nitrogen content,crop yield,and economic ben efits.The results showed that subsoiling can sign ificantly improve the soil structure and physical properties.In all subsoiling treatments,the depth of 35 or 40 cm at a 2-year interval was the most significant.The thickness of the plough layer in creased from 13.67 cm before the test to 21.54-23.45 cm in 2018.The thick ness of the hard pan decreased from 17.68 cm before the test to 12.09-12.76 cm in 2018,a decrease of about 40.07%.However,the subsoiling combined presowing tillage practice,that is,rotary cultivation or ploughing,was not significant for soil structure and physical properties.For all subsoiling treatments,the soil bulk density,cone index and soil three-phase R values of the 15-25 cm soil layer were significantly lower compared to single rotary cultivation.Subsoiling was observed to increase the soil alkaline nitrogen and water conte nts.The tillage patter ns that had subsoiling at the depth of 35-40 cm at a 2-year in terval combi ned with rotary cultivation had the highest alkali nitrogen and water contents,which increased by 31.08-34.23%compared with that of the single rotary cultivati on.Subsoiling can sign ifica ntly in crease the yield both of wheat and corn,as well as the economic ben efits.The treatment of subsoili ng at the depth of 35 cm at an interval of 2 years com bined with rotary cultivation had the highest ann ual yield and economic benefits.For this treatme nt,the arinual yield and economic ben efits in creased by 14.55 and 62.87%in 2018,respectively.In con clusi on,the tillage patter ns that involved subsoili ng at a depth of 35 cm at a 2-year interval along with rotary cultivation are suitable for the Huang?Huai-Hai Plain.

Response of yield increase for dryland winter wheat to tillage practice during summer fallow and sowing method in the Loess Plateau of China

Soil moisture is the most critical limiting factor impacting yields of dryland winter wheat(Triticum aestivum L.) and it is strongly affected by tillage practice and sowing methods. This study was to assess the link between sowing method and tillage practice during summer fallow and their subsequent effect on soil moisture and grain yield. Furthermore, we sought to identify a more appropriate farming management practice for winter wheat production in Loess Plateau region of China. The experiment was conducted from 2011 to 2013, using a two-factor split plot design, including subsoiling(SS) or no tillage(NT) during summer fallow for main plots, and conventional drill sowing(DS) or plastic film drill sowing(FM) for subplots. Results showed that the maximum soil water storage(SWS) was under SS×FM treatment with values of 649.1 mm(2011–2012) and 499.4 mm(2012–2013). The SWS during the 2011–2012 growing season were 149.7 mm higher than that in the 2012–2013 growing season. And adoption of SS×FM significantly increased precipitation use efficiency(PUE) and water use efficiency(WUE) compared to other treatments for both seasons. Moreover, adoption of SS×FM significantly increased yield by 13.1, 14.4, 47.3% and 25.9, 39.1, 35.7% than other three treatments during the two growing seasons, respectively. In summary, combining subsoiling during summer fallow with plastic film drill sowing(SS×FM) increased SWS at sowing and effectively improved WUE, thus representing a feasible technology to improve grain yield of dryland winter wheat in the Loess Plateau of China.

A ^(15)N-Labeling Study of the Capture of Deep Soil Nitrate from Different Plant Systems

The objective of this study was to determine the efficiency of different plant systems in capturing deep soil nitrate （NO3-） to reduce NO3- leaching in a field plot experiment using 15N labelling. The study was conducted on a calcareous alluvial soil on the North China Plains and the plant systems evaluated included alfalfa （Medicago sativa）, American black poplar （Populus nigra） and cocksfoot （Dactylis）. ^15N-labelled N fertilizer was injected to 90 cm depth to determine the recovery of ^15N by the plants. With conventional water and nutrient management, the total recovery of ^15N-labeled NO3--N was 23.4% by alfalfa after two consecutive growth years. The recovery was significantly higher than those by American black poplar （12.3%） and cocksfoot （11.4%）. The highest proportion of soil residual ~SN from the labeled fertilizer N （%Ndff） was detected around 90 cm soil depth at the time of the 1st year harvest and at 110-130 cm soil depth at time of the 2nd year harvest. Soil %Ndff in 0-80 cm depth was significantly higher in the alfalfa treatment than those in all the other treatments. The soil %Ndff below 100 cm depth was much lower in the alfalfa than those in all the other treatments. These results indicated that ^15N leaching losses in the alfalfa treatment were significantly lower than by those in the black poplar and cocksfoot treatments, due to the higher root density located in nitrate labeling zone of soil profile. In conclusion, alfalfa may be used as a plant to capture deep soil NO3- left from previous crops to reduce NO3- leaching in high intensity crop cultivation systems of North China Plain.

Causes, effects and control of seasonal frost action in railways

Seasonally cold climate and resulting frost action set great demands to railway track substructure in order to maintain Irack geomelry. Chal- lenges culminate on high-speed lines, where the tolerances for roughness are the tightest. Problems may result in highly increased Irack maintenance and need for temporary speed reslrictions. The causes of frost action can be associated with subsoil, subballast or ballast. The major concern in frost protection is to avoid the freezing of frost susceptible subsoil by using sufficient thickness of subballast and relying on non-fi＇ost-susctible subballast material. This paper provides an overview of the main research findings on the role of ballast, subballast and subsoil in frost acedon. In new comlruclion the material specificalions, design procedures and construction methods have been developed to ensure adequate performance of Irack subscatt, but special challenges exist in managing existing Wacks that were not designed for modem requirements. In order to perform cost-effective and sustainable track maintenance, it is necessary to recognize the problem areas and define the root-causes of problems. For locating the problem sections and defining the causes of defects, a sophisticated analysis based on integration of track geometry and ground penetrating radar （GPR） data has been developed and is summarized in this paper,

Water Availability for Winter Wheat Affected by Summer Fallow Tillage Practices in Slope Dryland

The tillage experiments for winter wheat were conducted on the slope farmland in Luoyang, Henan Province in the semihumid to arid loess plateau areas of North China. Different tillage methods including reduced tillage(RT), no-till(NT), 2 crops/year(2C), subsoiling(SS), and conventional tillage(CT)were compared to determine the effects of tillage methods on soil water conservation, water availability, and wheat yields in a search for better farming systems in the areas. The NT and SS showed good effects on water conservation. The soil water storage increased 12 - 33 mm with NT and 9-24 mm with SS at the end of summer fallow periods. The soil evaporation with NT and SS decreased 7-8 mm and 34 - 36 mm during the fallow periods of 1999 and 2001, respectively. Evapotranspiration(ET)with NT and SS increased about 47 mm during wheat growth periods of 2000 to 2001. Treatment RT and 2C had low water storage and high water losses during the fallow periods. The winter wheat yields with conservation tillage practices were improved in the 2nd year, increased by 3, 5 and 8% with RT, NT and SS, respectively, compared with CT. The highest wheat yields were obtained with subsoiling, and the maximum economic benefits from no-till. All conservation tillage practices provided great benefits to saving energy and labors, reducing operation inputs, and increasing economic returns. No-till and subsoiling have shown promise in increasing water storage, reducing water loss, enhancing water availability, and saving energy, as well as increasing wheat yield.

Ultimate Bearing Capacity of Subsoils to Marine Pipelines

Based on the theory of limit analysis, the Finite Difference Method (FDM) is established for evaluating the ultimate bearing capacity of subsoils to bear the unburied pipelines. The analytical results of bearing capacity of the ideal clay is given. The approach to bearing capacity evaluation of cohesionless subsoils without surcharge is suggested. The results from this method are consistent with those obtained from model tests.

Engineering Geological Problems of Levee Along Middle and Lower Reaches of Yangtze River

The levee along middle and lower reaches of Yangtze, about 3 600 km long, was built mostly on loose quaternary deposit with changeful complicated formation and geologic defects. Hence, during flood season, dangerous events occur frequently, which imperil the levee’s safety and pose great threats to life and property of people behind the levee. According to the exploration and investigation results, a classification of subsoil profile is made. And then the analysis on main engineering geologic problems, i.e seepage failure of dyke and bank slope instability, is conducted. The internal relations between main engineering geologic problems and subsoil profile are found out, which provides a scientific basis for the design of strengthening dykes.

Effects of Continuous Vertical Soil Pores on Root and Shoot Growth of Winter Wheat: A Microcosm Study

Round shaped, continuous vertical pores (CVPs) in the soil are typically created by roots and earthworms. CVPs with diameters > 2 mm are abundant in many agricultural soils. We hypothesized that potential effects of CVPs on shoot growth of winter wheat (Triticum aestivum L.) increase with: 1) decreasing availability of water and 2) decreasing availability of nutrients in the topsoil. We conducted a microcosm experiment with different irrigation regimes (Irr+/Irr-) and P concentrations (P+/P-), with or without artificially created continuous vertical pores (CVP+/CVP-). Winter wheat was cultivated for 16 weeks. In the bulk soil, presence of CVPs resulted in decreased root length in 20 - 40 cm but increased root length in 40 - 60 cm soil depth. In general, total root length of winter wheat in 20 - 60 cm soil depth was higher when CVPs were present or when P concentrations in the topsoil were elevated. Presence of CVPs generally had a positive effect on shoot dry matter and N uptake of wheat. In columns with high phosphorous concentrations but low soil moisture in the topsoil, presence of CVPs increased shoot dry matter by 66%;in contrast, the beneficial effect of CVPs on shoot dry matter was only 39% in columns with high nutrient concentrations and high soil moisture in the topsoil. In total numbers, however, the effect of CVPs on P uptake into the shoot was more pronounced when P concentrations in the topsoil were elevated. We conclude that CVPs can promote the exploration of the solid soil phase by high root-length densities, but adequate nutrient supply in the topsoil is essential.