137 lines
4.9 KiB
Plaintext
137 lines
4.9 KiB
Plaintext
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mu u
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‘REGD‘MMENDED SCALE 0? sum PARTICLE SIZES
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mm .
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[Alter McDonald Hal]
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rin- olay c a sea
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clay nimoles a 002
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sor n m . 0 oz
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sun: on . z.n
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lino 0,02 , o z \
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ooaiss 0.2 - 2
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GRAVEL z . so
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Fl"! 2 , s
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Moo-um 5 ~ 2::
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coaiu 2n . so
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CDEBLES so e 200
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STONES zoo , soo
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aouwsns sow
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ahsorphon.
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rural
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Hamus or humic decay and bacteria) producla pioyide
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colloids, as do llnely ground graphiio and silica, line
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clays lpariieics ol 2-200 millimioronsi such as illiies,
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henlonilc (usually deposiled on clay pans isom
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evaporaiion of clays in iuipellsiml), grain iiours and
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animal lgeiaunous) nours, eg iroin hooves, horns,
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sinew wislzs, album and so on aamna also seeiele
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polysacciurides which ioi-m soil gels,
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Son condilioncis which iorm slabie colloids are sold
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under a variely oi iradc names (ask a local agncullural
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supplieil, e g. Agrusuhem, lkedagzm. Tenasorl:®.
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which are hydrophiiir laliraci waleri as are many
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naniral gels irom grain ymduns and seaweed, Ware.
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conservanon iii up lo 50% is claimed lor some oi rhesc
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addirives Mosa arlilicial gels are Icryllc-based
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nacrylaniid polym) and supplied as granules able lo
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aosoro hundreds oi nines lheir weighr in wales. rhsy
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sie used hi gut eifed in nursery planla, row crops,
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Ilrw nee planiings m desens, and in rransplanling. The
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acrylics are applied ro soils al 5 log/ha or more, and
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conserye irrigalion waler by psevsnring eyaporaiinn
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lsiraii rurmer, New Zealand, Aug ‘34) These
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subshues are 0! value in seed penning.
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Calloids also loml hydvaphnblc irepei waleri
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snbshms such as lhose oi clays and some soil hingi
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produce. The surraces oi colloid panislcs are usually
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negalively chill-geld, as are rool hairs, and ihus aiiraer
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posinve ions ro ihsar suriaces, cg rhe posinve ions or
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sulphates nirrares, and iii meials lsodium, calcium
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magnesium, ironl Aboua 99; al such ions are so held
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in soils chepcr, i952), Colloids irom liumus are
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hundreds oi limes more eiiecme ihan clay colloids in
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ion exchange in soils
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Ammmua and sodium can dislodge lheac ions, and
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lhey can oscome av ilaiile lo planl ioois, which aliracl
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lliein by producing nogahyc rill charges wilh ioo
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much i-iushing by sodium, ihe calcium and meralhr
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ions can he losl io lcaching pnsceoaes and carried hi
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sueams, hence lo seas or lakes.
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Cullmds used in waier solienrng capruie cslcium
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ions and release sodium ions, allowing soaps lo laiher
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Ferric uxide colloids have pusml‘l‘ charges and glvl‘
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warer a brown srairi, iypicai oi waler: issuing lrom
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acid pears and pmc ioissls. ihe colloid paniclcs can lse
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nocculaled iaggmgaredl and selile our ii aluminium
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salrs lsulpholesi are added. and rhis may happen as a
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resulr oi acid rain, or can be induced Wirh ihe acid
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iorms ol any negarive parricles Sall also iloccuiares
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colloids up is rhe poinl where excess sodium
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dr/lorrulorcs days, wirh calcium and oiher ions, which
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is ihe efiocr ol high sall conconrrarions in dryiand soils
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loyer lcs ppm salli.
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Burning desnoys rhe colloidul properues ol surlace
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clays and is anoiher reason why descn soils leach our
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airer iiies. aurni clay panicles no longer farm (nVIul'dsi
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and become poor in iruneral nuri-ienls, which are rhen
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lound only in deep soil profiles Oeganie humus ionns
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blxk slimy pools on rop ol ihecoliapsed soils
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ir is rhe clay panicles and colloids lorganic and
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inorganic colloidal lhai oind waier and nurrienr in
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soils. in ihe oopics ai loasl, mosaol lhesc oolloids are in
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ihe biomass oi rho soil as cellular gels, or aie produced
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as shealhing maierial by soil omens wirhoui colloids,
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soil minerals rapidly leach our and become poor in
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nulrienl Fire. clearing, ploughing, and cuiiivarion
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desrioy such colloids and soil srnicrnre, as does extess
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sodium ions. rhus. iii hold and sachangc nuincnls, we
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as gardeners need lo develop narurai or arriiicial
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colloid conicni in soils, iiom where planr ml: and soil
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launa or llora derive iheir waier and ossenrisl
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numenls Very e clay is needed in sandy gardens lo
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cioalc a svll dal soil environmeni, and liie iorms are
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encouraged and developed by humus, mulch, and
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perenmal planl crops. Good soil siruciure lro hold ihe
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coflnlds) is developed iiy careiul easin husbandry,
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aogelhcr th iloeailaling additives such as gypsum
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and humus.
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solL WATER
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The waier conlenr oi soils is a soup oi iieehvrng
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organisms, dissolved gases and sairs, minerals, gels,
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and ihe washoii iiom ihrougliiall in lrees lwaxes,
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lnssi iree ”body wines"? Organic and inorganic
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paniclea are held in - warer soils have a widely
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vamblt wares-holding capaciry dependeni on rheir
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composirion and manure, so ihai sands absorb and
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ielain warer more quickly lhan clays, hul clays hold
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more walcr per unir volume Available water ihus
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varies horn 2% lsririace sandal lo 40-7. or more oi soil
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yehsine. We can assisr rhe quamuy held in dry sires by
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swallng, conrouring or rerracing, loosening soils,
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adding ilocsulanis, inrioducing aniricial or narurai gels
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lscaweeds or plaslic aoso-laisi, or lay placing a clay or
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103
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