Soil-Winged Subsoiler Interactions And Their Effects

Winged subsoiler is a subsoiling tool,which can improve the soil disturbance effectiveness at various depths and create an ideal soil structure by changing the wing positions.Nowadays it has been used frequently in arid field subsoiling.The information regarding to soil disturbance behaviors,soil structure formation and subsoiling effects under the impact of different winged subsoilers is still unknown.Therefore,discrete element method(DEM),finite element method(FEM),lab soil bin test,double-ring infiltration test and field test were used to systematically investigate winged subsoiler-soil interaction and their effects on field soil physical properties and crop performance.The main conclusions were drawn as follows.(1)Discrete element simulations and experiments of winged subsoiler-soil interaction.Relevant DEM parameters and contact models between soil and subsoiler were determined by physical test and the characteristics of northwest field soil.The winged subsoiler-soil interaction was investigated by developing the layered DEM tillage model with winged subsoiler.The results showed that wings mainly affected the soil disturbance area and fracture of soil above them;the significance for the effects of winged subsoiler on the lateral disturbance range and fragmentation degree of soil at various depths followed the rank:top layer(TL),and hardpan disturbed by arc section(HDAS),and hardpan disturbed by share section(HDSS).Addition of wings increased the disturbance area of HDAS,TL and HDSS by 47.52%,7.74%and 4.59%,respectively.The draft forces of share section(SS)and arc section in the hardpan(ASHP)were the main source of the draft force for winged subsoiler.Wings had the largest influence on the draft force of ASHP,followed by the draft force of ASTL.The results from DEM were basically consistent with these measured in the lab soil bin,indicating that the developed DEM tillage model can accurately simulate the tillage process of winged subsoiler.(2)Effects of particle size and particle size-distribution(PSD)on soil cutting forces and disturbance behaviours.With the increase of particle size,an overall increase trend was found for both soil disturbance area and fragmentation index while both draft and vertical forces decreased gradually.Increasing PSD gave an overall increase in draft force.Soil disturbance behaviours(e.g.soil rupture distance ratio,soil disturbance area,and soil density change rate of hardpan)and draft and vertical forces were significantly affected by particle size.The relative errors of simulated soil disturbance behaviours were lower;lower relative errors were found for simulated draft forces from DEM models with particle radii from 5 to 15 mm.When nominal particle radius was larger,soil disturbance behaviours were significantly affected by PSD at p<0.05.In contrast,both draft and vertical forces were significantly affected by PSD at various nominal particle radii(5-15 mm);moreover,the variation of draft and vertical forces became noisier when larger nominal particle radii or PSD were used.(3)Optimization of installation parameters of subsoiler's wing using discrete element method simulations.The upward angle and mounting height significantly affected both soil loosening efficiency and soil disturbance area ratio while mounting angle only significantly affected soil loosening efficiency.The significance for the effect of key factors on soil loosening efficiency followed the rank:upward angle,mounting height,and mounting angle.For soil disturbance area ratio,the significance for the effect of key factors followed the rank:mounting height,upward angle,mounting angle.To improve soil loosening efficiency and obtain a larger soil disturbance area ratio,it is necessary to appropriately reduce mounting height and upward angle of subsoiler's wing and increase wing mounting angle.(4)Effect of wing mounting height(h)on soil water infiltration characteristics.As h was reduced,the stability of soil water infiltration rate,vertical wetting front transport distance and accumulative infiltration and moisture content of soil from 10 to 30 cm from surface after infiltration gradually increased.The RMSEs calculated from the simulated soil moisture content and the field test results were less than 0.05 and R~2 was higher than 0.95,indicating that the mathematical models of soil water infiltration had a good accuracy.(5)Effect of wing mounting height(h)on field soil properties and crop performance.In the key growth period of wheat and maize,the soil moisture content of the treatments with small h(?115 mm)was higher in most depths.With the decrease of h,the grain yield of winter wheat and summer maize increased overall,and the increases of panicle number of winter wheat,kernel number and kernel weight per panicle of summer maize were the main reasons for above increases,respectively.