INDEX Aeration estimation 210-213; modeling 216-217 Aggregate breakup 20, 53-56 Aggregate bulk density 13 Aggregate size distribution 109 Aggregate stability 60-70, 83-86, 89, 90, 93, 224, 231, 240; rate of change in 225-226, 229-230; seasonal change in 90-93; stabilizing materials 226, 227-228 Aggregate strength 12-18, 78 Aggregate surface 109 Aggregation process 60, 61-62, 68, 70, 264 Anaerobiosis see Oxygen uptake Angle of contact 102 Angle of internal friction 16-18 Applied stress 27, 29 Area of disturbance 130-132 Bonding force 44-45 Boussinesq elastic theory 121 Boussinesq equations 147, 148, 149, 248 Bulk density 48, 132-133, 175-176, 264 CaO see Lime Charge characteristics 61-62, 62-68, 259 Clay fraction 65-66 Clod size distribution 109 Clod surface 109 Cohesion 16-18; and water content 82-83, 84; and wetting 86-88; development 81-86; loss of 73; raindrop impact 86; recovery of 82, 85-86; seasonal fluctuation of 90-93 Compaction 2-3, 38, 39, 73-80, 90, 91, 92-93, 121-123, 137-144, 158-160, 164, 166-167, 187-188, 190-192, 213, 214, 235, 242, 249, 252, 259, 264, 265-266; and root disease 215-216; by rainfall 39; deep 182-183; excessive 206-207, 217; measurement of 48; of aggregates 112; plant tolerance of 215; shallow 175-182; subsurface 233; wet 41 Compaction models 132-134, 137, 145, 234, 244, 267-268, 263; analytical 147-149; finite element 145-147, 244 Compressibility 66 Compression, secondary 138-140 Compressive strength 98-99, 100 Cracking see Fracture behavior Crescent failure 125-129 Critical-state line 142-143 Critical-state soil mechanics 144, 149 Crop residue 91, 251 Crop yield 224, 236, 251 Cropping sequence 93, 230 Cropping systems 223-225, 226, 228, 231 CSL see Critical-state line CTIS see Wheel inflation 269
270 Darcy's law 16 Deformation 23-32, 53, 98-99, 133-134; elastic 19-20, 148-149; flow type 41, 43, 44, 46; hardening type 43-44 Dispersibility and strength 62 Displacement by tillage 107-108; by roots 155 Draught force 121, 123 Effective stress 10-11, 15-16, 29-31, 53-56 Elastic deformation see Deformation Elastic materials 23-32 Energy dissipation and stress distribution 26 Equilibrium water pressure 56 Erosion 3-4, 69, 90-92, 102, 103, 251, 252 Flocculation see Aggregate formation Flocculation-dispersion behavior 61-62 Forages 217, 223, 257 Fracture behavior 23-32 Fracture theories 24-29 Freezing 38, 90-92, 93 Gas diffusion 157-160 Gaseous exchange 206-208 Horizontal force see Draught force Horizontal load 148 Hydraulic conductivity 18, 78, 190 Hydraulic properties 190-196, 198-199, 239, 241, 246 Inflation pressure 42-43 Inorganic colloids see Soil strength and clay fraction Inter-aggregate strength 39, 45-47 Inter-aggregate voids 38-39, 44 Inter-aggregate pore size 18-19 Intra-aggregate strength 39, 45-46 Ion diffusion 18-19 Ion mass flow 18 Kneading 20, 48 Lateral failure 125-129 Lateral rupture distance 130-131, 132 Lime 97-103 Liquid limit 66 Loading 12, 15, 17, 23, 24-25, 26, 40, 54, 55, 244, 248 Loading time see Stress duration Macropores 246 Manure 91 Matric potential 31, 32, 234, 235 Mechanical resistance 258 Microreliefmeters 253 Minirhizotron technique 250 Moisture ratio 54 Natural proces3 models 264-265 Negative charge characteristics see Soil strength Neutral stress 15-16 Nitrogen content 255 Organic binding agents 60-61
271 Organic matter content 255, 259 Organic soil conditioners 97-103 Oxygen uptake 157, 207-208 PBO see Organic soil conditioners Ped strength 235 Penetration resistance 18, 153, 155, 156, 176-177, 258 Permanent negative charge 64 ph see Lime, Soil strength Phytotoxicity 100 Plant growth 167-168, 235 Plastic deformation 19-20 PNC see Permanent negative charge Polybutadiene see Organic soil conditioners Polyvinyl alcohol see Organic soil conditioners Pore continuity 19-20, 78, 237 Pore-size distribution 19 Pore-water pressure 30-31 Pore structure 242, 252, 265-266 Porosity 40-41, 47-48, 101, 188-190, 212, 233, 237-238 Pressure transmission 74-77 Pre-consolidation load 77-79 Principal stress 140-142 Proctor tests 47, 48 PVA see Organic soil conditioners Radial stress 144-145 Raindrop impact 39, 86, 252 Rake angle 123-124 Random roughness 2 Recompaction 39, 40, 47 Reloading 12, 17, 40, 47-48 Ridge shape determination 109 Root and shoot weight 165-167 Root branching 156 Root depth see Root vertical distribution Root density 159, 161, 254, 255, 259 Root elongation 154-156, 170, 249, 250 Root elongation models 157 Root growth 164-167, 205, 207-208, 212-217, 234, 249, 265-266 Root growth models 216-217, 266 Root length density 176-180 Root-shoot ratio 256 Root system response 153-168, 249, 254 Root system models 153 Root system variability 180-182 Root vertical distribution 158-159 Roots, spatial arrangement 159-164, 249, 255, 256 Runoff see Erosion Ruts see Deformation, hardening Saturated hydraulic conductivity 102, 233 Seasonal fluctuations in soils 38-39, 257 Shear failure 15
272 Shear resistance see Shear strength Shear strain 244 Shear strength 3-4, 13-14, 64-65 Shear stress 25, 44, 56, 89, 139, 140-142 Soil cohesion 81-93 Soil disturbance 121-136 Soil failure 2, 125-129 Soil friability 32 Soil gas diffusion 206, 208-213 Soil pore space see Porosity Soil strength 10-18, 61-68, 154, 259; and displacement 107; and ph 63, 66-68; measurement 4-5; variation 64-68 Soil structure 153-168, 223-231, 240, 259, 265-266; models 262-263; variabil ity 245, 257 Soil surface level 242 Soil surface roughness 108-109 Soil water property models 198-199 Soil water retention 100-101, 188-190, 233, 239, 246 Soil water transport 188-190 Soil-water content 29-32, 49, 190, 224-225, 246, 257; and root growth 160; and soil contioners 99; and strength 64-65 Soil-water diffusivity 190-192 Soil-water flow, modeling 196-198 Sorptivity 190 Spatial variability 154 Stability of fracture process 26, 32 Strain energy 27, 29 Stress distribution 24-26 Stress duration 76-77 Stress isobars 248 Stress/strain behavior 14-15, 98-100 Stress/strain models 140-144, 146-148, 263-264 Structural form, rate of change of 224, 225, 230 Structural stability see Aggregate stability Surface roughness 251, 253 Tensile failure 23 Tensile strength J1, 64-65 Tensile stress 25, 30 Terzaghi see Effective stress Tillage 1-2, 23, 38, 39, 88-90, 91, 92-93. 105-115, 187-188, 192-196, 234, 236, 237, 241, 243, 245. 251, 254, 255, 256, 264, 265-266; and energy 106, 113-115; and soil structure 105-115, 240; soil biology response to 213-216 Tillage models 105-115, 124-132, 247, 262-263, 267-268 Tillage tools 105-120, 243; blades 113-114. 124-125; classification of 129-130; discs 114, 129-130; effects of 111-115; levelers 112; narrow tines 125-129; no secondary 217; rollers 111-112; rotavators 114-115; tines 112-113, 247 Tires see Wheels Tortuosity 20
Triaxial test 43, 47 Trophic processes 166-167 Tropical soils 59-72 Uniaxial compression 26, 47, 98 Uni axial tension stress 24 Unsaturated hydraulic conductivity 234 Unsaturated soil 53, 56 VCL see Virgin compression Vertical stress 74 Virgin compression 138-140 Void ratio 54 Volume fraction of aggregates 54, 55 Water transfer 157; models 162-164 Wetting see Cohesion Wheel deflection 42-43 Wheel inflation 42, 142-143 Wheel slippage 144-145, 244 Wheel-soil interface 42-44; compaction 11-12, 41-43, 74-76, 168-185; models 144-145; wheel load 42 273