THE IMPRINTER FORCE

Downward Acting Force = Upward Acting Force

  Imprinting Force or Pressure = Soil Load Bearing Capacity

Thus,   an   imprinting   roller   will   penetrate   or   settle   into   the   soil   to   the   depth   where the   opposing   forces   are   equal   or   balanced.   For   a   full-tooth   imprint,   these   forces balance   when   the   teeth   penetrate   the   soil   halfway,   because   of   the   embossing effect.   When   soil   load   bearing   capacity   is   too   high   or   the   soil   is   too   hard   for halfway   penetration   of   the   imprinting   teeth,   additional   weight   can   be   loaded onto   the   imprinter   or   the   soil   can   be   softened   by   ripping   or   wetting.   Usually   the best   alternative   is   to   add   more   weight   up   to   a   static   imprinting   pressure   of about 207. Imprinters    are    designed    to    have    an    adjustable    range    of    static    imprinting pressures    of    104    to    207    KPa    (15    to    30    psi).    For    the    2.43-meter    (8-foot) imprinter    with    straight    angles,    the    base    1816    kg    (2-ton)    weight    gives    an imprinting pressure of about 104 KPa (15 psi). Loading   the   imprinter   with   an   additional   1816   kg   (2   tons)   raises   the   imprinting pressure    to    about    207    KPa    (30    psi).    Thus,    as    a    rule    of    thumb,    the    static imprinting   force   per   30   cm   (foot)   of   roller   length   should   range   from   227   kg   (500 pounds)   when   the   imprinter   is   unloaded   to   454   kg   (1000   pounds)   with   a   full load. Imprinter   loading   is   accomplished   by   filling   the   imprinting   roller   core   with   water and   by   mounting   water   tanks   or   soil   boxes   on   the   imprinter   frame.   Tanks   or boxes   are   mounted   on   both   sides   of   the   seed   box   such   that   the   weight   is balanced   over   the   axle   of   the   imprinting   roller.   Tanks   are   the   same   size   as   the imprinting   roller   core,   whereas   soil   boxes   are   about   the   size   of   the   seedbox. The   outer   side   of   soil   boxes   should   be   removable   to   expedite   emptying   of   the well settled soil. Tillage,   before   imprinting,   kills   existing   vegetation,   covers   plant   litter,   breaks down    soil    structure,    and    encourages    weed    growth.   Thus,    tillage    should    be avoided   as   an   alternative   to   adding   weight   to   the   imprinter   frame.   However,   if tillage   is   required   because   of   deep   soil   compaction,   ripping   is   less   destructive than   disking.   Also,   mycorrhizal   inoculum   can   be   injected   several   inches   deep behind   the   ripping   shanks. Another   alternative   to   ripping   hard   soils,   is   to   imprint them   twice.   For   instance,   if   the   first   imprinting   is   only   one-half   of   the   full   depth, the   second   one   will   be   markedly   deeper   because   imprinting   teeth   tend   to   get   in gear with the first imprints and then bite deeper into the soil. The   static   pressures   of   104   and   207   KPa   (15   and   30   psi)   are   based   on   the   soil contact   area   resulting   from   the   halfway   penetration   of   6   teeth   for   the   240   cm   (8- foot)   imprinter.   The   general   formula   for   the   number   of   teeth   in   contact   with   the soil   is   1.5   times   the   number   of   in-line   teeth   or   0.75   times   the   length   of   the imprinting   roller   in   feet.   The   quantitative   soil   mechanics   of   land   imprinting   is extraordinarily   complex   and   poorly   understood.   Thus,   the   analysis   presented here is only a greatly simplified first approximation. Finally,   it   should   be   noted   that   the   actual   or   dynamic   imprinting   pressures   are much   greater   than   the   static   pressures.   Soils   with   a   hardness   of   690   KPa (100psi),    as    measured    with    a    cone    penetrometer,    can    be    imprinted    by    an imprinter   producing   a   static   pressure   of   207   KPa   (30   psi).   Thus   the   momentum of   the   revolving   imprinting   roller   apparently   increases   imprinting   force   by   more than   3   times.   Just   as   stepping   lightly   on   soft   soil   leaves   no   footprints,   stamping, running    and    jumping    does.    Another    explanation    is    that    the    imprinted    soil weakens   the   adjacent   non-imprinted   soil,   thereby   lowering   the   imprinting   force required as the imprinter rolls along. Under   field   conditions,   soils   usually   vary   greatly   in   hardness   from   point   to   point with   some   areas   requiring   ripping   and   some   not.   A   tractor   equipped   with   a ripping   tool   bar   and   a   draw   bar   for   towing   the   imprinter   allows   the   operator   to selectively   rip   only   the   hard   spots   while   imprinting   the   whole   area   as   shown   in Fig. 1. Click   on   the   menu   to   left   or   Dr.   Robert   Dixon   picture   on   right   to   view   S ummary and References.

The    imprinting    tow    frame    can    be loaded    using    the    tractor's    hydraulic system   and   3-   or   4-point   hitches   or   by soil    boxes    attached    to    the    tool    bar frame.

The    hydraulic    system    that operates   the   dozer   blade   is used   to   load   the   steep-slope imprinter.