LAND IMPRINTING METHODS (page 2) Prepared for Discovery Park, Safford, Arizona, by Ted St. John, Ph.D. Land Imprinting Compared To Related Methods  Land   imprinting   was   developed   for   improvement   of   the   degraded   pasture   lands   and abandoned   farmlands   that   came   to   occupy   much   of   Arizona   and   the   southwest during   the   twentieth   century.   Imprinting   was   not   the   first,   nor   was   it   the   most   widely used   of   the   approaches   that   were   developed   for   dry   seeding   of   these   lands.   Instead it   was   developed   to   specifically   address   the   problems   of   poor   water   infiltration   and poor    soil    aeration    caused    by    sealing    of    the    soil    surface.    Imprinting    has    been successful   in   large   part   because   it   does   a   better   job   than   other   methods   of   meeting the   infiltration   problem,   while   providing   surface   heterogeneity   and   other   benefits   that were   the   strengths   of   the   earlier   methods.   Because   a   land   imprinter   is   not   always available,   and   because   an   individual   project   might   in   some   cases   favor   an   alternative method, some of the other soil preparation methods will be briefly reviewed here. Broadcasting:   Simple   broadcasting   of   seeds   is   generally   regarded   as   wasteful   and ineffective,     but     is     sometimes     used     when     better     methods     are     unavailable. Broadcasting   is   the   method   used   in   aerial   seeding   of   burns,   where   the   land   areas   are vast   and   even   the   fastest   land-based   methods   are   too   expensive.   These   efforts generally   result   in   well-fed   birds   and   rodents,   and   some   germination   of   the   weediest plant species in the seed mix. Scarification:   A   rough   land   surface   is   far   superior   to   a   smooth   or   hard   surface   for seed   establishment,   and   broadcasting   may   be   considerably   improved   by   roughening the   land   surface   with   a   tractor-drawn   harrow   prior   to   broadcasting.   Other   implements used   for   the   purpose   include   other   types   of   plows.   After   broadcasting,   the   harrow may   be   used   again   to   partially   burry   the   seeds,   giving   some   protection   from   seed- eating   animals.   Scarification   may   not   be   practical   on   ground   with   grasses   and   other small plants that are considered desirable. Chaining: A   special   case   of   scarification   is   the   application   of   seeds   at   the   same   time that   undesired   vegetation   is   removed   by   chaining.   Chaining   consists   of   dragging   an anchor    chain    between    two    tractors,    pulling    out    shrubs    and    small    trees    while roughening   the   soil.   Broadcast   seeds   are   partially   buried   or   fall   into   the   crevices   in the   roughened   ground,   providing   improved   conditions   for   germination.   Chaining   is not   suitable   for   very   rough   or   steep   terrain,   are   areas   where   the   existing   shrubs   and trees are considered a desirable part of the vegetation. Drilling:   One   of   the   most   widely   used   planting   methods   is   the   rangeland   drill.   This tractor-drawn   device   uses   disks   to   cut   a   groove   in   the   soil,   and   then   drops   seeds   into each    groove.    The    machine    then    covers    and    tamps    the    soil    over    the    seeds. Rangeland    drilling    has    given    good    results    over    extensive    land    areas    in    the southwest,   and   continues   to   be   a   valuable   method.   It   is   most   suitable   for   retired farmlands,   where   the   ground   is   level   and   smooth,   and   relatively   free   of   rocks,   debris, and   existing   vegetation. The   best   seed   drills   have   separate   bins   for   seeds   of   different sizes,    because    the    dispensing    devices    often    perform    poorly    where    a    seed    mix includes   a   range   of   seed   sizes   and   shapes.   The   rangeland   drill   is   unsuited   for   steep or very rough and rocky terrain. Contour   furrowing: A   shank   attached   to   a   powerful   tractor   is   sometimes   used   to   form a   trench   that   follows   the   contours   of   the   hillsides.   Seeds   are   then   placed   into   the trench.   The   trench   is   able   to   give   protection   from   direct   sunlight   and   wind,   and   is thought   to   place   the   newly   emerging   plants   within   reach   of   moisture   stored   in   deeper soil. Pitting:    Several    kinds    of    devices,    including    hand    labor,    can    be    used    to    scoop depressions   in   the   soil,   in   a   method   that   shares   some   characteristics   with   land imprinting.   The   depressions   may   be   very   large   and   widely   spaced,   in   which   case they   are   best   formed   with   the   blade   of   a   bulldozer.   Smaller,   regularly   placed   pits   may be   formed   with   a   series   of   shanks   on   the   toolbar   of   a   tractor.   The   toolbar   is   raised and    lowered    as    the    tractor    moves,    giving    a    regular    pattern    that    superficially resembles   the   pattern   left   by   an   imprinter.   A   machine   made   from   a   disk   type   plow may   also   form   regular   pits.   A   section   of   each   disk   is   removed   with   a   cutting   torch, leaving   disks   that   alternately   cut   and   leave   high   ground   as   the   device   is   pulled   by   a tractor.   Mechanical   pitters   are   difficult   to   use   on   very   steep   or   rocky   ground,   or   in areas    where    there    is    valuable    preexisting    vegetation.    However,    such    sites    are suitable   for   hand   pitting. A   hoe,   shovel,   pick,   or   other   hand   tools   may   be   used   on   any terrain   that   is   accessible   to   workers.   In   this   way   pitting   has   been   used   to   establish vegetation   on   slopes   too   steep   for   any   mechanical   method   other   than   hydraulic seeding. Hydraulic    seeding:    "Hydroseeding"    is    an    expensive    method    not    devised    for improvement    of    large    land    areas.    It    has    been    used    in    some    revegetation    work because    the    equipment    is    familiar    to    landscape    architects    who    might    design revegetation   projects   in   urban   areas.   If   done   well,   the   method   works   on   slopes   that may be too steep even for hand labor. Livestock:   Large   animals   make   depressions   in   moist   soil   that   collect   rainwater   and other   resources.   If   seed   are   present,   the   hooves   of   the   livestock   press   the   seeds   into firm   contact   with   the   soil.   These   "living   imprinters"   can   produce   results   that   are superior   to   almost   any   of   the   mechanized   methods.   However,   it   is   important   that   the livestock   be   removed   quickly   once   their   work   is   done,   since   the   same   animals   that plant   the   seeds   can   quickly   overgraze   the   resulting   vegetation.   Livestock   may   be   the method   of   choice   on   remote   sites   where   cattle,   horses,   or   other   large   animals   are available and can be removed within a few days. Comparisons   of   methods: All   of   the   available   methods   have   been   used   with   success in   some   conditions,   and   all   have   failed   in   other   conditions.   Certain   characteristics   of the methods make some more suited for particular jobs. Broadcasting,   scarification,   and   rangeland   drilling   allow   water   to   run   downhill   and collect   in   gullies   or   other   low   spots,   leaving   most   of   the   soil   without   stored   moisture. Livestock,   imprinting,   pitting,   and   contour   furrowing   trap   runoff   throughout   the   land surface,   permitting   even   storage   of   soil   moisture.   Unless   the   land   is   quite   level,   these methods have a substantial advantage in the arid west. Seeds   germinate   best   when   in   firm   contact   with   the   soil.   This   is   always   achieved   by livestock   and   by   properly   executed   land   imprinting,   and   is   sometimes   achieved   with rangeland   drilling.   Pitting   and   scarification   leave   most   of   the   seeds   in   only   loose contact with the soil. In    rough,    rocky,    or    steep    terrain,    the    suitable    methods    usually    are    limited    to broadcasting,    hand    pitting,    hydroseeding,    livestock,    and    certain    types    of    land imprinting.   Contour   furrowing   may   apply   in   some   cases.   If   there   is   already   desirable vegetation   on   site,   the   same   list   applies.   If   there   is   a   desirable   cryptobiotic   crust (layer   of   algae   and   lower   plants   on   the   soil   surface),   pitting   and   contour   furrowing   are not suited since they destroy this valuable layer. If    the    soil    is    badly    overgrazed,    non-vegetated,    or    freshly    graded,    mycorrhizal inoculation   may   be   the   only   way   to   create   a   healthy   diverse   plant   community.   The inoculum    must    be    placed    below    ground    to    be    effective.    Scarification,    chaining, contour    furrowing,    pitting,    and    land    imprinting    may    all    be    used    to    incorporate mycorrhizal   inoculum.   However,   the   only   way   to   produce   a   continuous   below   ground network   of   mycorrhizal   fungi,   a   necessary   part   of   most   healthy   native   ecosystems,   is with   closely   spaced   inoculum.   Only   scarification,   land   imprinting   and   very   closely spaced pits offer evenly spaced inoculum.