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TRNG I HC LT

KHOA NNG LM

BI GING TM TT

(Dnh cho sinh vin ngnh Nng hc

v Cng ngh sau thu hoch)

HC PHN

K THUT NH KNH

Ngi bin son:PHM NGC TUN

THNG 06/2008

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MC LC

BI 1 PHN LOI NH CHE PH ............................................................................ 31.1. Cu trc nh knh:.................................................................................................... 31.2. Cu trc nh c mi che:.......................................................................................... 8Bi 2: ............................................................................................................................ 10XY DNG NH CHE PH ..................................................................................... 102.1. V tr nh knh v nh mi che: .............................................................................. 102.2. Lp t b khung nh knh cng nh cc loi nh che ph khc:......................... 14

2.3. Cc dng mi lp: .................................................................................................. 232.4. Cc dng lung, mng, chu trng cy s dng trong nh knh:........................... 292.5. Cc loi gi th trng cy trong nh knh: ............................................................. 342.5.1 Yu cu chung ca gi th trng......................................................................... 343.5.2 Thnh phn ca gi th: ....................................................................................... 352.6. Cc h thng iu khin thng dng trong nh knh:.......................................... 45Bi 3: ............................................................................................................................. 46MI TRNG NH CHE PH ................................................................................. 463.1. Cc yu t mi trng trong nh che ph: ............................................................ 463.2. Cc h thng iu khin v cch iu khin mi trng trong nh che ph:........ 473.2.5 H thng ti: ..................................................................................................... 54Bi 4 .............................................................................................................................. 56BO DNG NH CHE PH................................................................................... 564.1. S cn thit ca vic bo dng nh che ph:....................................................... 564.2. Cc nguyn nhn gy h hng nh knh:............................................................... 564.3. Cc bin php khc phc v bo dng nh knh nh che ph: ......................... 56Thut ng chuyn mn ................................................................................................. 58TI LIU THAM KHO ............................................................................................ 59

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BI 1

PHN LOI NH CHE PH

1.1. Cu trc nh knh:Cu trc nh che ph l tng th cc b phn cu thnh nh che ph. V cutrc cbn ca mt nh che ph gm 4 phn:

- Phn nn mng: y l b phn lin kt gia nh che ph vi mt t. Bphn ny thng c lm bng cc loi vt liu khc nhau nh: gch, b tng. Phnnn mng c th xy ton bng vin xung quanh nh, xy cch khong, hoc cngc th ch xy nn mng gi cho cc tr chnh ca khu nh.

- Sn nh, mt sn: c lm bng cc vt liu khc nhau. Thng thng, ivi nh che ph hoa, vt liu sn nh thng lm bng t, ct y cng chnh l vtliu ch yu ca gi th, lung trng. Trong nh che ph trng hoa, cc li i c th

lm bng b tng hoc gch lt ng. Tuy nhin, yu cu ca vt liu sn nh l khnng thot nc. Nh vy, xt v kh nng ny, nu vt liu lt sn l b tng th yucu phi xem xt n h thng tiu nc. i vi nn t th kh nng tiu ncthng tt hn b tng. Sn nh thng c xy theo hng nging v mt pha m bo kh nng tiu nc trong nh che ph. Sn nh c th xy ton b nh che

ph hoc c th chia theo , theo cc li i xung quanh cc lung trng.- Phn mi che: lm bng cc vt liu trong (knh, mng nha trong, knh

nha,...) cho php nh sng xuyn qua.- Phn sn nh: l b khung chnh ca nh che ph, c th lm bng cc vt

liu khc nhau nh: st, cc loi hp kim, khung nhm, v cng c th lm bng g,

tre, ..Phn khung sn nh c thc to thnh bi cc vt liu hnh ng c ni

vi nhau. di cng nh din tch nh che ph c lp t theo thit k vi cchnh dng khc nhau nh: vung, hnh ch nht, hnh a gic,...

Mi mt khung nh che ph theo thit ku ni n cc ch tiu sau: chiu dinh che ph, chiu rng nh che ph, chiu cao mng nc, s nhp, bc nhp, chiudi nh tnh theo nhp, chiu rng nh tnh theo mng nc, din tch phn hnh lang,din tch phn ng nh che ph, tng din tch nh che ph, chiu di ca ra vo, slng, cu trc v ln cc ca thng gi,..

Phn ny gm c cc chi tit theo sau:

Ridge: l nh nc ca nh che ph.Vertilator: l thng gi l nhng b phn c th di chuyn c ca nh che

ph cho l nhng b phn c th di chuyn c ca nh che ph cho php luthng gi mt cch t nhin. Chng c thc lp mt bn vch, trn mi hoc cth lp trc tip trn nh (nc nh).

Eaves: mi hin

Purlin: (n tay) l b phn lp trn mi, dc theo chiu di ca nh knh vmi upurlinc lp bulong gn vi mi khung gin ko.

Sill: ngng caChords: giy cn

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Strut: thanh chng

Rafter: rui

Sidewall: vch bn

Sidepost (Anchor support posts): tr bn, l cu trc chng ch yu ca nhknh,tr bn c xy cn i dc theo nh knh v c xy pha trn chn btng.

Curtain wall: vch chn

Ground level: mt t

Footer: chn (mng)

Hnh 1.1 Tng thca mt nh mi che Plastic ni tip hin i.

Hnh 1.2: S cu trc b khung mt bn ca mt Nh knh.

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Hnh 1.3: Cu trc ca mt nh knh n gin

C 3 loi cu trc chnh ca nh knh:1.1.1. Nh knh c mt vch dnh lin vi mt cng trnh khc (attachedgreenhouse):

y l kiu nh knh n gin nht. Mt s kiu thuc loi nh knh ny cs dng sn xut cy trng mang tnh thng mi v ng thi cng c thc sdng trng by cy trng trong cc quy hng bn l, cho cc khu vn trung tm,vn phng lm vic, v c th trng by trong nh. im thun li ch yu ca loinh knh ny l gim c chi ph xy dng, v qu trnh xy dng tng i ngin. Tuy nhin, do chng c xy dng p st vi cng trnh, c th b cng trnhche chn trong hng chiu sng, nn thng thiu nh sng. ng thi cng rt kh

iu khin s thng thong v nhit nh trng. C ba kiu nh cbn thuc loiny: Nh knh p tng: Kiu ny c xy dng da vo mt cng trnh hin ti.

nh ca mi nh knh c gn mt bn ca cng trnh v mi nghing ra xa khicng trnh. hn ch mc che bng ca khu cng trnh th loi nh knh ny nnc xy dng theo hng Nam ca cng trnh.

Hnh 1.4: Nh che ph kiu p tng

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Nh knh hai mi p tng- Kiu nh ny gm 2 mi vi nhng thanh rui cchiu di bng nhau v bc tng cui cng c p st vi mt cng trnh. Loi nhknh kiu ny c ng dng ph bin hn loi p vch. Bi v chng c th thyc nhiu ni v ni chung, chi ph xy dng v chi ph si m cho nh trngcao hn loi p vch. Nh knh nh di ngc thit sn y l loi nh knh c lm sn, c

th tm c nhng nh knh kiu ny vi nhng mu kch thc ph hp vi nhngkhung ca s c kch thc chun. Kiu nh loi ny thng c kch thc nh, ch sdng trng by hoa cc gia nh, khng ph hp vi kinh doanh mang tnh chtqui m. ng thi loi ny rt kh iu khin cc iu kin nui trng.

1.1.2. Nh knh c lp:

Nhng nh knh sn xut qui m thng mi thng l nhng cu trc clp c hai mi. y l loi nh knh c cu trc phc tp hn c cn i khng

gian c tn dng tt cho nhng li i thun tin v nhng dy nhn ging. V cnhiu u im hn, loi ny c thiu khin c yu t ngoi cnh nh nh sng,nhit , thng thong. Nh cc loi nh knh hnh ch A (ph bin nht) c dngnh knh c mi khng i xng thng thch hp cho cc vng xy dng nhngkhu vc c a hnh i dc.

C loi nh knh c mi hnh vm chp (quoset) hoc hnh chp.

Loi nh knh c lp c nhiu u im nh:

- Mi trng diu khin

- Vic thng thong gi d dng hn- Vic tu b, bo tr d dng hn so vi loi nh knh c vch ta.

Tm li c 8 loi nh knh:

1. Even-span: nh c mi i xng ch A

2. Uneven-span: loi nh c mi khng i xng

3. Lean-to: loi nh knh ta vch

4. Quonset: dng vm chp

5. Gothic arch: dng chp

6. Curvilinear: dng hnh cong

7. Curved eave: dng hnh cong c mi hin.

8. Dome: dng vm

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Hnh 1.5: Nh che ph kiu mii xng chA:

Hnh 1.6: Nh che ph kiu vm

1.1.3. Nh knh lin tc(connected greenhouse).

L loi nh knh ph bin hn c, mt s cc phn nh knh n thng cgn st bn nhau, gim c chi ph lp knh bn trong cc bc tng k bn. S spxp cc lung trong nh knh thng khc nhau. Mt s s lp t cho nhn ging vnhnh tt khng gn cc bng mt cch cnh, s sp t chng khc nhau ty theoloi trang thit b nh cc xe nng, xe b in ... c dng mang nhng ngn tv cy trong v ngoi nh nhn ging.

Loi nh knh ny phc v cho hnh thc sn xut trn qui m rng ln vchuyn nghip. Gia cc nh knh c gn vi nhau bng cc mng xi (gutter). Minh knh c cu trc ch A, cu trc mt mi nghing, hoc cu trc vm v c xydng ni lin nhau.

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Hnh 1.7: Nh che ph ni tip

1.2. Cu trc nh c mi che:

Thc cht cu trc nh c mi che cng nh cu trc nh knh. Tuy nhin, n

gin hn cu trc nh knh. V cbn th cu trc nh c mi che cng gm 4 phn:nn mng, sn nh, khung sn v phn mi che. Nhng vt liu lm mi khng phil knh, m s dng cc loi vt liu trong khc nh polyethylene, v mt s loi chtliu nylon tng hp khc,... y l nhng vt liu tng i r tin, chi ph xy dngthp hn so vi cc loi nh che ph bng knh, do loi nh che ph v cc cc nhche ph ci tin c s dng rng ri qui m nh h gia nh.

Hnh 1.8: Dng nh knh c lp, dng hnh bn cu.

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Hnh 1.9: Dng nh knh ta vch.

Hnh 1.10: Dng nh knh chA ni nip.

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Bi 2:XY DNG NH CHE PH

2.1. V tr nh knh v nh mi che:

Sau khi nghin cu mt cch t m v kiu dng ca cc loi nh knh,chng ta phi xc nh v tr lp t nh knh. Nhng nhn t cn quan tm khi kimtra xc nh v tr xy dng nh knh. N bao gm:

2.1.1 t ai v kh hu:

Xem xt cn thn t ai v kh hu l mt yu t rt quan trng trong vicchn v tr nh knh thng mi nu mun n tn ti mt cch tit kim v phngdin cnh tranh vi cc nc thch hp hn. Mt ngi lm vn khng chuynnghip trong nh knh mc d anh ta c th khng chn nhng vn lm vic t nht

bit c cc nguyn tc ca kh hu v tm quuan trng ca n.

iu kin kh hu l mt yu t rt quan trng trong vic chn la v tr xydng nh knh. Do bc ny phi ht sc cn thn, bi v mi loi cy trng thchhp vi mt iu kin kh hu nht nh. Mc d thit k cc h thng iukhin iu kin tiu kh hu bn trong nh knh, nhng s thay i ln ca iu kinkh hu bn ngoi v s chnh lch qu ln ca iu kin kh hu gia bn trong v

bn ngoi nh knh nh hng rt ln n cc h thng iu khin cng nh cytrng bn trong nh knh. Kh nng v nh sng, nhit , m, sng mui, tc gi, l nhng yu t kh hu cn c xem xt k cn c xc nh v tr xy dngnh knh cho tng i tng cy trng c th theo k hoch c d tnh.

2.1.2. mCc khu vc gn vi nhng khu vc c lng nc ln v cc khu vc ma to

c m cao; v vy, nhng khu vc trng cy qu dy lm cho tc thot hi ncqua l cy qu nhanh. m cao ca khng kh khng chnh hng n sinh trngca cy m cn gy bnh cho cy.

Nhiu ngi lm vn xy dng nh knh v mong mun n c hnh dngging nh cc nh knh khc. iu ny hon ton khng ng. Chn la v xem xtmt cch cn thn iu kin thi tit xc nh v tr xy dng l v cng quan trngv khng th coi thng, vn quan trng nht cn quan tm l cng chiu sng.

2.1.3. nh sng ttKhi xem xt mt ci nh c th hnh dung c thit k nh th no xung

quanh nh knh l rt thng thng cho vic thit k mt nh vi y tin nghi vlai b nh knh nhng v tr khng tha ng. Tuy nhin, iu ny nhiu ngi chorng s sp nhp nh knh nh mt nt c trng trong nh c v yu t thm m vthc t. N to ra mt s ph thuc thch hp cho ni v cng l cch tit km chovic lm vn trong nh knh v si m gn lin vi h thng ca gia nh.

Tuy nhin, vic xem xt ny khng nh hng n tm quan trng cbn cas sp xp cu trc ti ni n s tip nhn nh sng tt, mc d r rng nu nh knh

c s dng ch yu tiu khin v s tiu khin ny mong mun trnh c tng

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nhit n mc khng th chp nhn c vo bui tra v chu snh hng mttri bui chiu.

nh sng l rt cn thit cho nhiu cng vic trng trt, c bit cho vic nhnging v to iu kin cho s sinh trng ca nhng cy a sng trong nhng thng

ma ng. V vy, y l s la chn cbn v tr cho nh knh nu mun l l tngnu cn thit v phng din tip nhn nh sng, c bit trong nhng thng mang. Mt v tr nm pha c nhiu nh sng ca ngy t thng ba n thng mi cth l sm m tht s cho phn ln ma ng khi nh sng l thp.

Hnh 2.1: Kh nng che sng ca hng ro 2 ma khc nhau.

2.1.4. Yu t gi

V tr xy dng nh knh c cn thit phi che chn hay khng?Cu hi v nh sng v vic che chn c quan h cht ch vi nhau. Mt nh

knh c thc xy dng trong mt vn cnh gn lin vi nhng hng cy cao hoccc hng ro v tham gia tt vo iu kin nh sng yu. mt vi khu vc khng thtrng trt c kt qu tt m khng trng cy che chn

Trong nhiu khu vn, ch che chn gi trn thc t khng cn thit v ton bdin tch chung khng cn n vn ny. Khng c s hng dn ca t nhin tthn l to dng cho cy vng k cn, thm ch tt hn so vi li khuyn ca nhngngi lm vn trong vng, mc d iu ny c th khng phi quan tm.

Gi c thng nhiu mnh khe khng th tnh trc bng cch thi ngi nhhoc i ni hoc to ra cc khu vc no ng mnh m ln pha trnh gi ca cc bctng v qut.

Btrai chn gi:

Cung cp ch che thng c quan tm hn ci vi ton b vn hn lc bit i vi nh knh. Cc quy lut ging nhau c s dng cho c hai.

Cc tm che chn cng ngy nay hu nh khng c quan tm. Chng hunh khng lm ngng gi. Chng ta cn lm lch hng gi ln trn, sau axung vi mt tc yu hn, i khi to ra s no ng ng k ngay pha sau tmchn.Tt c cc dn chng ca cc nghin cu mi nht cho thy r l mi trng c

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dng tm chn gi 50% l l tng cho vic lm chm tc gi, trnh c s lchhng v s no lon.

Cc tm chn ny c hiu lc khong cch gp 10 n 12 ln chiu cao catm chn, iu ny c ngha l trong gii hn thc t, nu hng ro chn cao 2,4m s

c hiu lc trong khong 24 30m trli. Vng c kh nng che ti a l khu vc t 5n 6 ln chiu cao ca hng ro tc l khong 12 15m trong trng hp hng rocao 2,4m, khong cch khng c che chn cn c quan tm. Mt hng ro caovi nhiu cy dng cao, v phng din khc, s to nn mt s bo v tt cho mtvng rng ln nhng c th s l vn che chn rt gi to vo ma h.

Hnh 2.2: M hnh chn gi cho mt nh knh n gin

2.1.5. Hng xy dngXc nh hng xy dng nh knh cng l mt yu t cn thit lin quan n

kh nng nhn nh sng v gi. Thng thng xy dng nh theo hng theo hngNam-Bc l tt nht m bo kh nng nhn nh sng ca nh knh. Tuy nhincng c nhng nh knh c xy dng khng theo hng Nam-Bc, lc ny th cclung trng trong nh knh cng nn c xy dng cho ph hp vi hng nhn nhsng lm sao c s phn b nh sng ng u cho cc lung cy trong sut thigian chiu sng.

2.1.6. Ch nc:Cng nh kh nng cung cp nc ca khu vc xy dng nh knh cng c

quan tm. Chng c ngha ht sc quan trng i vi hiu qu cng nh s tn tica nh knh c lu di. S dng ngun nc sch l cn thit cho hot ng canh knh. Nhng iu kin thun li khc nhin, nhin liu, cht t,... cng nnc xem xt.2.1.7. Kh nng thot nc ca t: cng rt quan trng trong vic xc nh v trthit lp nh knh. V tr xy dng nh knh nn t v tr tng i bng phng vis thot nc trn v di b mt. Xy nh knh trn nhng vng t cng bng phngth nhn cng cng nh cc vt liu khc s di chuyn mt cc d dng hn.

2.1.8. Cc iu kin khc:

Cc iu kin vt ai, tng t v r cy cng cn phi xem xt mt cch cnthn.

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Nhm gim bt cc chi ph u t v thun tin cho th trng mang li hiuqu kinh t cao, ngi ta cn quan tm n khong cch ca v tr thit lp nh knh sovi ng giao thng, th trng tiu th, v ngun nguyn nhin liu lin quan,..

Th trng (ni tiu th cc sn phm nng nghip): trc khi u t vo vickinh doanh bng nh knh, nn xc nh r th trng tiu th, cng nh sc mua vgi cu ra ca sn phm.

Gn ng giao thng: tin cho cng vic chuyn chphn bn, nhn hngv giao cc sn phm th nn xy dng nh knh gn ng chnh. Hu ht cc sn

phm t nh knh u c vn chuyn bng xe chhng hoc xe ti mt s cshot ng vi quy m ln. Nu hot ng kinh doanh ca nh knh nh mt i l bnl, th phi lp t gn cc v tr cng cng d thu ht c khch hng.

Nhng vng quy hoch (Zoning Regulation): trong nhiu vng dn c, khngcho php xy dng nh knh. V vy chng ta cn kim tra li cc khu vc quy hoch

i vi mt s vng t bit trc khi mua hoc chuyn nhng t ai phc v choxy dng nh knh.

Nhn cng: phi nh hng c lng nhn cng c th cung cp, trong phn chia thnh ngun nhn cng c kinh nghim v nhn cng cha c kinh nghim.y l yu t quyt nh n tin cng nh hiu qu hot ng ca doanh nghip.

Kh nng m rng quy m: nh knh hot ng cn c k hoch m rng quym trong sau ny. C th lc u ch l mt nh knh c lp, nhng cng phi c khoch mrng quy m, xy thm thnh nh knh lin tip. Nh vy, y cng l yut quan trng trong nh hng v pht trin kinh doanh nh knh.

Hnh 2.3: Kh hu

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Hnh 2.4: Hng xy dng

Hnh 2.5:ngi v hng phn x ca nh sngi vi cc loi cu trc hnhdng nh knh khc nhau

2.2. Lp t b khung nh knh cng nhcc loi nh che ph khc:

2.2.1. inh v v lp t b khung nh knh: sau khi xc nh v tr xy dng nhknh, tin hnh nh v v lp t b khung nh knh.

Khung nh knh c thc thit k theo cc hnh dng khc nhau: hnh vung,

hnh ch nht, hnh lc gic,...Khung sn nh knh hay nh che ph c thc ch to t cc ngun vt liu

khc nhau. Cc vt liu c th l st, nhm, g, tre,... trong , khung nhm l loivt liu c nhiu u im v c s dng nhiu nht. Hin nay, i vi cc doanhnghip sn xut cy ging cng nh cc sn phm rau qumc qui m cao ngi tathng s dng loi nh knh c khung sn nhm. Mt s loi nh knh c ch totheo kiu lp sn v c lp t ti ch bng cc ghp ni bulng, vng m, ai c,khng c kt cu phi hn.

Trc khi xy dng nh knh, cn phi c mt bng (nn mng) to nn sc

chng ca b khung nh. Vic xy dng nn mng c thc tin hnh, nhng thng

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thng cc chn c xy bng b tng. Nn mng c xy dng di ng dynh v gii hn din tch v c t ti v tr khong gia theo nh v tr ca tr bn.

H thng ng nc v ng dy in nn c b tr v lp t trc khi xydng nn mng nh knh. Lp t cc ng ng ca h thng in nc, xy dng

nn mng b tng mt cch bng phng, vung vn cn i hp l l ht sc quantrng ph hp vi b khung sn nh sau ny.

Mt s nh knh cn xy dng c nhng bc tng bn (sidewalls) hoc nhngvch che. Vch che c xy dng gia chn v thanh tr bn. Chiu cao cavch che bn di chn ny khong chng vi chc centimet (cm)v ph khp chuvi ca nh knh. Thng dng bng nhng khi g, gch, than x, hoc c th dng btng xy thnh vch che chn.

Da theo bn v thit k chun b sn, nh du v tr dng nh knh trnmt t, thng ngi ta dng nhng cc nh du c kch thc chnh xc 2,5 x

2,5cm v c chiu di ti thiu l 30cm. ng nh cc u tin vo mt im ckhong cch nht nh so vi mt ng thng cnh no nh hng ro, ng ihay mt to nh, v s dng cun thc o bng kim loi xc nh chiu di canh knh, sau dng mt cc khc nh du v tr ny, ch s dng cch o ttm n tm cho mi cc. Nhkim tra xem hng cc c nm trn cng mt ngthng vi hng ro hay to nh hay khng, ng thi m bo rng chng theo nghng nh ban u. Ch rng y l chiu di ca nh knh, l hng ca cclung cy, do chng phi ph hp vi hng ng Ty hay Nam - Bc theo thitk. S khng khc bit my nu b sai lch mt vi t hng ny qua hng khcso vi thit k nh, tuy nhin, i vi kiu lung ng ty, s tt hn nu b lch

v hng bc, cn vi kiu thit k bc nam, b lch v hng ng s tt hn.Vi mt nh knh hnh vung thch hp, tt hn l nn p dng kiu lung chy

tng sang ty cn bng s truyn nh sng vo ma ng v xun. Ti nhngni xy dng nh knh nhng khng p ng cc yu cu v hng, khng th chnc hng xy tt nht m nh knh phi dng theo c hng ng - Ty ln Nam -Bc. Nh vy duy tr lng nh sng phn bu cho cc lung cy vo ban ngyv th chng ta phi c nhng cc b tr cng nh cch sp xp cc lung cy cho phhp.

Tip theo chng ta nn xc nh khong cch hai cc mt cch chnh xc, ngchng chc chn vo t. Vi mt nh knh theo kch thc trung bnh vi chiu di t2,5 3,2m, cn mt bng di, phng, khng b vnh v mt ng ni v o phng.i vi nh knh di hn th nn s dng cc cc trung gian, kim tra xem thnghng gia cc cc nh v bng cc si dy nhc cng gia hai cc. Mc d vychng ta cng cn kim tra li ln cui bng phng cc cc tr bng ng ni v (ngthng bng dng bt nc).

Cc nh knh nh hn thng c dng mt mc ngang bng cnh, kiuln vi mt mng xi c th hi nghing v mt pha, theo nh li khuyn ca ca nhsn xut, s to iu kin thun li cho s lu chuyn nuc trong mng. Vi loi nhknh thng mi, c bit l dng nh knh c nhiu gian, th cn phi lp mt mng

xi nc m bo cho qu trnh thot nc mt cch nhanh chng theo mng xi vkhng chy ngc li qua lp knh khi tri ma.

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Sau , ng nh mt chic inh vo tm ca mi cc, phi cn thn dngthc th ph hp o rng ca nh knh mt cch cn thn ch khng nn

phng on. C th s dng loi thc tam gic c to t 3 ming g thng c chiudi 0,9m, 1,2m, v 1,5m (y l loi thc chuyn dng c 1 gc vung v 2 gcnhn). Kim tra li xem chnh xc ca cc gc c to thnh trn thc ny bng ke. Thc tam gic ny nn c t ngay vo chng inh mt gc cc v mtcnh nn c bng gch dc theo si dy cng gia hai chn cc. Sau khi cnhkia ca gc vung, t mt si dy dc theo v buc cht vi cc t pha ngoi xc nh rng ca nh knh. Tip tc o dc theo dy v thm cc xc nh chiurng. Lp li qu trnh ti cc gc cn li, v kim tra 2 cc theo chiu dc, ng thikim tra xem cc ng cho c bng nhau hay khng. Cng cn thit nn iu chnhsqua mi thn khp vi nhauBy gith nng cc cc gc ln v ng inhvo tm ca chng. Cui cng t mt si dy bn v cng vo mi cc gc phcho ra hnh dng/ung nt ca cn nh bng cch s dng cc mu g, hoc dngthm cc, cch pha ngoi nh knh 0,6 0,9m cng vic c th tin hnh trn nnmng ca nh knh m khng c trngi bi vic di chuyn cc cc gc v cc dyra pha ngoi theo yu cu.(Xem hnh 2.6)

Hnh 2.6:nh dng nn mng nh knh (din tch nh knh)

2.2.2. Nn mng:y l mt cng vic rt quan trng c lin quan n rt nhiu yu t, b phn

ca nh knh sau ny. Xy dng nn mng nh knh ph thuc vo tng kiu nh tngcu trc nh knh.

Vi mt s lai c th ca kiu nh knh Dutch light, ch cn t cc khi trnmt t bng, mc d y khng phi l mt cch thch hp i vi nh knh c sdng lu di, thiu tnh bn vng hay vic ngn s di chuyn ca cc dng nc mtrong t xung quanh. y l cch thc tc chp nhn v s dng bi tnh titkim v kinh t ca n, hoc khi iim dng nh knh ch l a im tm thi. Yucn ca mt nn mng l tng l phi gi cho nh knh hon ton thng bng vvng chc ngay c khi c gi bo. Yu tng gi nht, nu c, s ph thuc vonhiu nhn t, v c bit l ph thuc vo kch thc thc t ca nh knh c dng.

Nn nghin cu tht k s dng hoc sch hng dn c th p dng vi nh knh.Cc khi ny c tht (hng) km vi nh knh; hoc thay vo bn c th xy nnmng bng gch hoc b tng c nh cc. i vi nhng nh knh khngchuyn cu trc na gch dy 11 25cm s ph hp, v n thng chnh xc vi

rng ca bt k khi nn no. Trong trng hp ny, sau khi xc nh chnh xcng gia y nh knh, o mt rnh rng 10 23cm v su 18 20cm, hoc su

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hn nu t mi c san bng tip xc vi phn t cha b xi. iu ny khngphi lc no cng thc hin c. Trn 3 phn gch vn, 2 phn ct th, 1 phn ximng ri tri mt lp dy 8 10cm v nn lp ny cho cht bng cch s dng mt

bn phng, nng, s dng mt niv (ng thng bng dng bt nc) mt trn kim tra phng thng xuyn. Trong trng hp cn thit phi xy ton b nnmng bng gch c dy 23cm, nh trong trng hp iim dng dc, hay ivi nhng nh knh ln, rnh nn rng 30 35cm v su 12 15cm, mc d trongnhiu trng hp nn 1/2 gch s vng chc nu c gia c thm bng cc ccchng. Trong mt s trng hp nh knh c tht trc tip ln nn mng m khngcn cc khi nn, trong trng hp ny s cn c bu lng lng vo nn mng ti vtr thch hp, hoc thay vo c th s dng ci chem (bn ging). Lun lun i nnmng kh cng li ri mi bt u xy dng. Trong tt c cc trng hp nn t dytrli ng v tr c v gi chng cng khi cn c th kim tra xem chng c tuntheo kch thc nh nh hay khng. Trc khi xy cc tng i din, nn kimtra li rng v chiu di, bi v gch c khuynh hng khng thng hng, c bitnu chng c xy bi nhng ngi thn khng c kinh nghim.

Vic nghin ngm cc quyn catolo v nh knh ch gip chng ta thy mtbc tng pha ngoi hon chnh m khng c quy nh v cc ca, vic ny s dnn nhng bc lng tng tr khi c mt on dc thch hp. Khi t cc khi nn,nn cha v tr ca ngang bng vi mt t, mt s sp xp hp l hn, min l cmt bc ngn bng b tng

Nhng iu trn c v khng quan trng, nhng theo thi gian chng s to nns khc bit rt ln trong vic qun l nh knh. Li khuyn l v tr gn ca nn caomt cht trnh nuc ma chy vo nh knh, vn ny c th xy ra nu nh nhknh xy trn nn t dc.

Ngay ci vi vic xy dng mt bc tung thp th k thut xy cng khcnhau, nhng vic trn ct v xi mng theo t l 3:1, kim tra dy v bng phng cami vin gch hay cc khi b tng tht k th ngay c ngi thxy khng chuynnht cng c th thc hin c. Ch rng nu s dng gch c mt trang tr th mttrang tr nn quay ra ngoi, nu khng th chng s nhanh chng b mt mu.

Hnh 2.7: Xy nn mng nh knh bng b tng

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Hin nay, mt s loi nh knh khng xy dng phn mng bao quanh ton bnh knh m ch xy dng chn cho cc tr nh knh. Loi mng kiu ny tng in gin, t tn km nhng cng kin c khng km cc kiu nn mng khc.

Hnh 2.8: Xy dng chn tr.

2.2.3 Qu trnh xy dngi vi mt vi loi nh knh yu cu chn tng thp khong 75cm th phi

xy chn tng cn thn, nu khng th c th s pht sinh vn sau ny. Rt t khinh knh dng sn c d kin cho ph hp chn tng s xy. Nhng ngi t lmthng s dng phng php xy chn tng nh knh theo thit k thng thng cnhng tm kim loi trn nh tng chng ng vin nh. gim bt chi phxy dng nh knh, ngi ta mua li vt liu khung qua s dng, tuy nhin phi cnthn tho ht phn g, qut mt lp sn trc khi bt u xy dng, c bit l phncn st li ca thanh vin c phi c tho b ht. Nn s dng nhng chic inhc m km, bi v inh bng thp s d dng b g.

Hnh 2.9: Lp rp b khung nh knh dng ng (tube)C rt t trc trc trong vic dng mt nh knh c rp sn, c bit nu c

thi gian nghin cu qua s dng nh c cung cp t nh sn xut. Mt s

quyn sch hng dn rt chi tit, mi phn c nh du v minh ha bng s rrng vi nhng con s chi tt ca tng b phn. i vi cu trc bng hp kim th

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thng dng cc ct chng v mt mt trn t, ri sau xy mt ct chng, tip tcvi mt mt ri ti mt kia trc khi dng mt ct chng khc,.. Mi nh v h thngthng gi nn cha lm sau cng.

Hnh 2.10: Lp cc ct chngvo tr chnh.

Hnh 2.11: Lp t cc thanh ruiv ct chng vo tr chnh.

Hnh 2.12: Lp t b khung nhknh, nh mi che.

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Hnh 2.13: Mng thot nc (xi)c lp bn hng nh knh.

Hnh 2.14: B khung nh knh hon thnh.

Ton b b phn lp knh ca nh knh bng gc lm sn c dng theomt th t tng t, nhng vn cn s gip bi v cc b phn ny thng nng.

Nu lm nh knh bng g trn chn tng t xy, th nn dng khung chnh trc khit ng vin nh.

Khi lp knh, cho d tin trnh khc nhau, ngi ta thng lm phn mi nhtrc,. tip n l chn ct chng, cha cc vch gn sau cng trnh trng hpkhi gp gi to chng s thi xuyn qua b khung. Mt im rt quan trng khi lm bt

c loi nh knh no l ch ni lng cc l thng hi vo ban m, c bit nuchng c lp knh, nu khng th chng c th gy ra nhiu h hng.

Nhn mnh s cn thit ca vic cnh nh knh mt cch an ton khng ltha, hy cho xi mng cng li truc khi dng ton b kin trc ng gi.

Ch nn lp knh khi thi tit kh, bi v c bt mt tt v bng mt tt ukhng th bt kn knh nu nh chn song lp knh bt, mt khc, lm vic vi knhlc cn t l rt nguy him. Vi nh knh bng hp kim, tt c nhng ch ni mngnc hay cc phn chnh khc nn c hn kn bng mt tt hoc nhng vt liu thchhp khc.

ch no c mng nc, bm a nc t mi nh xung nn c lp tn ch thot nc hay thm nc ph hp, v khi nh knh c xy dng trn a

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hnh dc c th cn phi xy dng mt con mng dc theo nh knh bn pha cao hn ngn nc r vo nh knh.

Hnh 2.15: Nh plastic ni tip

Hnh 2.16: Nh knh c lp khung kim loi.

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Hnh 2.17: Dng nh knh c lp khung gc kch thc nh (thngtrang

tr)

Hnh 2.18: Nh knh ta vch bng khung g(trang tr)

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Hnh 2.19: Dng nh plastic khung kim nhm 2 mi khngi xng.

2.3. Cc dng mi lp:2.3.1. Nh knh (cc vt liu che ph ca loi nh knh ny hon ton c lm bng

knh): Vt liu knh cha 70% dioxide silicate (SiO2). Knh c bn cao, thi gians dng c th ko di 25 nm. Knh trong c kh nng cho nh sng xuyn n 90%.

Ngoi ra ngi ta cng s dng loi knh mlm vt liu che ph cho nh knh.Trong vic xy dng nh knh, khung g hoc kim loi c dng ln v gn

ln nhng thanh trt g hoc kim loi vi nhng knh gn cht trn . Nhngloi khung sn nh knh bng nhm lm sn cng c cc nh sn xut a chung,v hin nay loi nh knh ny c s dng tng i rng ri. Chu u n mt sni M, ngi ta cn s dng loi knh mlm mi lp cho nh knh em li nhsng khuych tn, ng nht.

Nh mt thc t ni chung, nh knh c sn bn ngoi bng mt lp vitrng mng hoc sn nc trng khi bt u thi tit m p ca ma xun. iu nygip phn chiu phn ln nng lng bc x ca mt tri, nh ngn nga c sgia tng nhit ln cao trong nh knh. Tuy nhin, lp vi trng ph bn ngoi qudy c th lm gim cng nh sng xung mc thp khng mong mun.

Nhn chung th chi ph xy dng nh knh thng cao hn cc loi nh che phkhc, tuy nhin, i vi s lp t cnh v s dng trn qui m rng ln vi thigian kinh doanh tng i di th cc kiu nh lp knh ny trnn u vit hn ccloi nh ph bng nha gi thp nhc m t trong phn sau.

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2.3.2. Nh knh ph bng nha:

Nhng khung nhc ph vi cc loi tm nha khc nhau th ph bin ivi nhng cu trc vn nh nh cng nhi vi nhng khu lp t thng mi ln.Mt vi loi vt liu nha sn c, kh nh v khng t cho php xy dng nh knh

vi gi thp hn nhiu so vi vic dng knh. Thng thng cc loi nh che ph bngnha chc xy dng mt cch tm thi hoc cc nh sn xut nh, tr khi xydng cnh hn bng nhng tm ph gi cao nh nhng tm bng si thy tinh.

Nh knh ph bng nha th kn hn nh lm bng knh, do lm gia tng m v sng nc trn cy c bit vo ma ng. Tuy nhin, vn ny c thc gii quyt bng vic duy tr s thong kh mt cch thch hp bng cch s dngcc h thng iu khin khng kh tng.

Cc loi vt liu thng s dng i vi kiu nh che ph ny nh:polyethylene, nha vinyl, mt s loi vt liu nha tng hp khc,

2.3.2.1 Polyethylene:y l cht liu r nht nhng c thi gian s dng ngn nht. Loi vt liu nythng hay b hng vo ma h v phi c thay th mt nm mt ln hoc hn;thng thay vo ma thu s dng trong sut ma ng. Polyethylene c kh nngcn tia cc tm lu hn nhng c phn t hn. dy c khuyn co l 0,1 0,15mm.

cch ly tt hn v gim chi ph si m vo ma ng, c th s dng loipolyethylene 2 lp. Hai lp ny cch nhau bi mt lp kh c thi cng phng lmko di tui th ca polyethylene nhhn ch tc hi ca gi v lm gim m vhn ch nc ng bn trong nh che ph.

Nh che ph ph bng mt lp polyethylene s mt nhit vo ban m hoc voma ng nhiu hn so vi nh c lm bng knh v polyethylene cho php chuynnng lng nhit tt v cy vo nh che ph d hn nhiu so vi nh knh.

Knh ngn hu ht cc bc x hng ngoi trong khi polyethylene th khng cnc tia hng ngoi.

Polyethylene c kch thc rng ln n 1,2m. Do , khi lp rp cc vng cgi mnh ngi ta thng s dng li dy hoc vi cho mng polyethylene.

i vi vng c kt hp chn nui cc loi gia sc, gia cm th nn lp lithp xung quanh khi rch tm nha.

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Hnh 2.20: Mi nh che ph bng plastic dng

vm

2.3.2.2. P.E gn sng (Woven polyethyelene)thng dng cho nhng nh che ph cmi xp c. Vt liu ny c cht U.V, nga c hi nc ng mt trong plastic,loi ny c th cho nh sng xuyn qua n 80%. bn t 5 nm.2.3.2.3. Polyvinyl Fluozide (PVF) loi vt liu ny c bn trn 10 nm. C khnng anhsangs xuyn qua rt tt, v c cht chng tia U.V. Loi ny c cht lngtt nh knh.2.3.2.4. Polyvinyl Chloride (PVC) c bn di hn P.E. Tuy nhin y l mt loivt liu c tnh tnh in, ht in. Do , thng hp thu cc ht bi nh lm bn vtliu v lm gim kh nng cho nh sng xuyn qua. y l loi vt liu c kh nnghp thu I.R v gic nhit vo ban m.

2.3.2.5. Ethylene-Vinyl Acerate Copolymers (EVA) l loi vt liu rt cht, bn vt tin nn ngi ta thng t s dng.2.3.2.6. Polymethyl Methacrylate (Acrylic) l loi vt liu rt tt. Chu ng cvi thi tit, nh hn knh, nh sng vn xuyn qua tt. Loi ny cng gn nh knh,nhng nhc im ln nht ca n l sau thi gian s dng lu di chng d ho vngmv lm cn trnh sng.2.3.2.7. Risid sheet plastic (tm nha cng)

L loi mng mc, trng, dai, hn hp ca polyethylene v nha vinyl cngc th dng c. Mng ny c th cn bc x mt tri tt hn v vn mm do hn nhit thp vo ma ng so vi polyethylene. Di nhng loi mng nh th nhit t dao ng hn di nha trong cho nn n tt cho cc cy trng trong nh knhvo ma ng.

Vic dng hai mnh nhm kp gia tm ph polyethylene cho n c gichc vo khung em li kt qu l tit kim ng k thi gian v sc lao ngtrong cng vic hng nm.

2.3.3. Nh knh ph bng si thy tinhLoi vt liu ny l cc tm pano cng gp np hoc phng bng cc tm si

thy tinh gn vo tm nha c s dng rng ri cho vic xy dng nh knh. Sithy tinh th chc, bn, nh v d dng vi a dng v rng, di v dy. Ch nn

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dng vt liu trong, dy 1mm tr ln v nng 1,0 1,5kg/m2c bit dng cho viclm nh knh. S dn truyn nh sng ca vt liu ny c xu hng gim dn theo thigian. Si thy tinh l t nht trong cc loi vt liu m ty.

Ngoi ra, trong mt vi trng hp ngi ta cn s dng tn che lp phnmi. Tuy nhin loi ny thng t c s dng. Bi hn ch ca chng v vn iutit nh sng v nhit bn trong nh knh.

Hnh 2.21: Nh plastic dng vm lin tip.

Hnh 2.22: Nh che ph plastic dng vm lin tip.

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Hnh 2.23: B khung nh plastic lin tip:

Hnh 2.24: B khung nh plastic lin tip

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Hnh 2.25: B khung nh plastic lin tip:

Hnh 2.26: Dng nh plastic vm hkhung kim loi.

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Hnh 2.27 : Dng nh che ph c khung tre

2.4. Cc dng lung, mng, chu trng cy sdng trong nh knh:

Trong nh knh ngi ta thng trng cy trn lung, chu hoc cc loi gitrng khc:

2.4.1. Mng trng:

i vi cc nh knh trng rau, hoa ngi ta thng trang b thm cc mng gi

th. Loi mng trng ny c sn xut mt cch chuyn dng, v c trang b choph hp vi cc loi cy trng khc nhau. Gi th cha trong cc mng ny c th lt, cc hn hp trn hoc cng c th l cc hn hp gi th nhn to khng cha t.

Chng hn, i vi cy c chua, ngi ta cng trng trn cc mng gi thkhng cha t m cha mt loi gi thc bit chuyn dng cho cy c chua, t 4mng trn mi nhp nh knh. Cc mng gi th ny t trn mt mng thot ncngoi, dng thot v thu hi lng nc ti d trong qu trnh chm sc.

u im ca phng php ny l n gin, d vn hnh, mang li:

oNng sut cy trng caoom bo s dng ti a din tch nh knho To iu kin gi sch mi trng ti ao Cy sch bnho Chi ph thpo H thng thot thu hi nc thi hon chnh

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Mng trng cl thot nc

Mng chanc thi

kp

Hnh 2.28: Cu trc ca mng gi thtrng c chua.

2.4.2. Lung trng: Cy trng trong nh knh cng c thc trng trn lung. Cclung trng ny cng c chun b tng t nh cc lung cy trng ngoi ngrung.

C cc dng lung trng khc nhau, v vic la chn kiu lung trng cng phthuc vo i tng cng nhiu kin mi trng v kh nng iu tit cc iu kin

ca nh knh.

Hnh 2.29 : Lung trng cy

2.4.3. Chu trng cy:2.4.3.1. Khay nng trng cy:

V cbn y l nhng khay bng g, nha hoc kim loi nng vi nhng lthot nc di y. Chng c tc dng gieo ht hoc to r cho cnh gim vchng cho php di chuyn cy con y mt cch d dng khi cn. Nn dng cc

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loi g bn nh tng, bch hoc g lm loi chu nng. Cc loi chu nha vm km c nhiu kch thc khc nhau. C 2 loi c th xp lng vo nhau v th chcn ni bo qun tng i nh. Trong xu hng cgii ha, nhng flat ln cvichc cm c lm thnh nh nhng tm pa-let c th di chuyn c bng xe nngsau khi trng cy hoc cnh gim c r.

Hnh 2.30: Khay nha m cy.

Hnh 2.31: Loi gi trng cy theo .2.4.3.2. Chu t st

Nhng chu hoa bng t st quen thuc lu nay vn c dng trng cycon d thm, d mt nc v nng. Chng d b v dng hnh trn ca chng khng ckinh t v ch. Sau khi s dng lin tc, s tch ly mui gy c gia tng nn cn

phi ngm trong nc trc khi dng li. Tuy nhin, chng c thc tit trng bng

hi, c th dng li v l mt loi chu ph bin.

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2.4.3.3. Chu nhaChu nha trn v vung c nhiu tin li; chng c th dng li, nh v t

chim din tich ct gi, bo qun v chng c th xp chng ln nhau v khng thm.Tuy nhin, mt s loi d vv cn di chuyn cn thn mc d cc loi khc lm bng

polyethylene th mm do v kh chc. Cc chu vung cng c lm thnh nhngti 8 hoc 12 ci d vn chuyn hn. Cc chu nha (v chu nng) khng th tittrng bng hi c nhng mt s nhng tc nhn gy bnh cho cy thng thng cthc loi b bng cch ngm nc nng 70o C trong 3 pht m khng lm hngnha.

Hnh 2.32: Cc dng chu nha trng cy trong nh knh.

2.4.3.4. Chu bng si

Than bn, g v c b sung phn bn c p thnh nhng dng chu khcnhau: hnh trn hoc vung, vi kch thc t 5 10cm. Chng kh v s giclu di. Nhng chu ny c th b vi khun lm cho thi ra v c b sung vo t,

cung cp thm cho cy trong qu trnh trng. Chu than bn c cng dng tt nht trng cy trong mt thi gian ngn v sau t vo mt chu ln hn hoc a ravn. Chu than bn trng trong mt thi gian di s hng v m khng thay i vc th b vvn khi di chuyn. Trong khi , nu khng gim cho chu th r skhng bm vo thnh chu v s pht trin theo hnh xon c.

Nhng chu c kch thc ln c lm bng si c trn nha ng c thdng cho vic trng cy ging. Nhng chu ny c thc s dng trng trc tipv chng cng hy trong t.

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2.4.3.5. Cc khi than bn hoc si

Cc khi nguyn liu rn (c khi c l sn) trnn ph bin nh mtmi trng gieo ht hoc mi trng to r cho cnh gim, c bit cho nhng loihoa nh cc v trng nguyn. Phn bn thng c b sung trc tip vo nguyn liu

trng. Mt loi c lm bng than bn nn cht v s nra khi thm nc, v nh gim cnh hay gieo ht. V cbn nhng khi ny tr thnh mt phn ca trngcy v t vo trong t cng vi cy. Nhng khi ny khng ch thay th chu mcn l hn hp dng nhn ging.

2.4.3.6. Giy p parafin v cc chu styrofoamKhi nhng loi ny c c l thot nc, chng lm thnh nhng chu tm

thi cho vic trng v cy chuyn cy con. Loi gi trng cy ny tng i r v nh,v cn khng gian bo qun nh.2.4.3.7. Chu bng giy n ph nha ng

V phng din thng mi nhng loi ny c mt s c v l nhng chutrng cy tm thi thch hp. Chng r, chc, nh v d xp chng ln nhau. Chu cthc lm bng giy xy dng c x l nha ng, un cc mnh giy ngkch cthnh nhng ci ca hnh vung, y mbng cch t chng vo nhng ngngi l st trng c th mc trn mt t.

2.4.3.8. Chu kim loiHng trm hng ngn cy m c trng v bn mi nm trong nhng hp

kim loi vi cc kch ckhc nhau. Thng nhng hp ny c tn dng t cc nhmy hp, nh hng ln v l bnh m. Nhng hp ny cng c th dng chun bcho trng cy. C loi c un ln sng v lm nh dn xp chng ln nhau v c

c l thot nc. Chng c trng men lm chm s g st. Cc my trng cy c pht trin tn dng nhng hp ny, vi my ny mt ngy c th trng c trn10.000 cnh gim hoc cy con mt cch nhanh chng. Cy trng c di chuyn mtcch d dng bng nhng hp c lm nh dn bng cch ln ngc v tin ren. Cchp kim loi khng c lm nh dn phi c ct bt mt mt bng ko ct hphoc ko ct tn c th di chuyn cy.

nhng vng c nhit ma h cao, s dng nhng hp sng mu (trnghoc nhm) c th thc y s pht trin r bng cch trnh s ph hy nhit cho rm thng gp cc hp mu ti s hp thu nhit ng k nu phi ngoi nng. Ngoira, nhit ca t trong cc hp kim loi c chiu hng cao hn trong cc hpnha.2.4.3.9. Cc ti polyethylene

Cc ti polyethylene nh c cc lc c di thot nc c thcy cc vt liu gi th xp to r nh trn chu vi vermiculite v c t trngi nhn ging vi ming ti m. Mi mt cnh gim ca cc loi cy d ra r nh ccc gim vo mi ti. Nhng ti ny sau c thc t di mn che v chmsc cho n khi cnh gim ra r, cng cp th c chuyn vo ti trng hoc trngtrn cc lung sn xut.

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Hnh 2.33: m cy trong ti polyethelene.

2.5. Cc loi gi th trng cy trong nh knh:C nhiu loi nguyn liu s dng lm gi th trng cy, chng bao gm nhng

loi nguyn liu sau:

2.5.1 Yu cu chung ca gi th trng

Vic la chn gi th trng l mt trong nhng vn quan trng nht linquan n hiu qu ca sn xut. Mi trng khng chnh hng n cc bin php

k thut chm sc cy trong nh che ph, m cn nh hng n chi ph vn chuynv s hi lng ca khch hng sau khi mua bn. Mi trng sinh trng p ngnhng chc nng quan trng chung trong s sinh trng v pht trin ca cy trngnh:

- S thng thong v kh nng gim: gi th trng phi m bo c m thch hp cho s pht trin ca cy, v ng thi c kh nng duy tr c khng khkhuch tn trn b mt cho s hot ng v pht trin ca r cy. Nu khng c s luthng trao i khng kh cho r cy th s sinh trng ca cy s b chm li v do ,s lm chm tr thi v thu hoch v khng p ng nhu cu theo thi im ca th

trng.- Kh nng gi phn: gi th l mi trng cung cp dinh dng cho cy trng.

pH ca gi th trng cn c m bo trong sut qu trnh sinh trng ca cym bo cho cy ht c dinh dng. Thng thng cc loi cy trong nh che phyu cu pH khong 5,5 6,5. y cng l pH cn thit c th gi li dinhdng trong gi th v phn gii chm cung cp dn cho cy.

- Gi cy trng ng vng: gi th trng cy cn phi c rn gi cho cyng vng trn gi th. Nhng loi gi th nh c th khng to cho cy thngvng trn gi th.

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- Gi th c th ti s dng v c gi tr s dng: nhng gi th m sau mi vtrng c th tn dng ring l hoc kt hp vi mt vi loi vt liu khc trng cycho v sau.

3.5.2 Thnh phn ca gi th:

Hin nay mt s loi gi th hn hp c trn t cc thnh phn, trong cmt thnh phn ch yu l t. t c trn vi cc vt liu khc to thnh mt gith tng hp thch hp vi yu cu ca tng loi cy.

Mi trng khng t l cc loi gi thc lm t cc vt liu hu cv vc, c th lm t xc b ca ng thc vt nh xda, tru hun, dn si, kt hpvi mt s loi phn hay bt c xay t xc bng vt nh bt c, vc hn,

Sau y l c im gi tht v mt s loi gi th khng t ph bin:

2.5.2.1 t:t bao gm l mt hn hp c 3 pha, pha rn, lng v kh. cy pht trin

thch hp nhng vt liu ny phi c t l thch hp.Pha rn ca t gm c dng v cv hu c. Phn v cbao gm phn cn tn

d li ca m sau khi phn hy do cc qu trnh bin i ha l ca thi tit. Ccthnh phn v cnh vy khc nhau v kch thc t ht si cho n cc ht keo khnh ca t st, kt cu ca t c xc nh bng t l tng i ca cc ht c kchthc khc nhau. Cc ht th to c tc dng chnh nh mt khung cho cc phn cnli ca t, trong khi phn t st keo ca t c vai tr nh ni d tr - cht dinhdng m cy c th hp thu c. Phn hu cca t bao gm c sinh vt sng vcht. Cn trng, giun, nm, vi khun v r cy thng cu thnh dng cht hu c

sng, trong khi nhng phn cn li ca ng vt v cy cc giai on phn hy khcnhau to thnh nguyn liu hu ccht. Phn cn li sau khi mc ra (c gi l tmn) rt keo, gip gi nc v cht dinh dng cho cy.

Phn lng ca t, dung dch t, c hnh thnh t nc c cha cc khongcht ha tan vi lng khc nhau cng nh O2 v CO2. Cc nhn t khong, nc vc th mt t CO2c cy hp thu t dung dch t.

Phn kh ca t quan trng i vi s pht trin ca cy trng. Trong t bnc v thot nc km, nc thay th kh trong t m n gip cung cp oxy cho cycng nh vi sinh vt hiu kh chng tn ti.

Kt cu ca t da vo t l tng i ca ct (ht c ng knh 2-0,005mm),ph sa (ht c ng knh 0,05-0,002mm) v t st (ht c ng knh

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2.5.2.2 Ct

Ct bao gm nhng ht nh ng knh khong 0,05 - 2,0mm c hnhthnh do s tc ng ca thi tit ca cc loi khc nhau, thnh phn khong ca n

ph thuc vo loi . Ct thch anh thng c s dng cho mc ch nhn ging

bao gm ch yu l phc silica. Loi c s dng trong vic trt va l loi thngthng thch hp nht cho vic to r cho cnh gim. Ct l thnh phn nng nhttrong tt c cc mi trng to rc s dng. Nn phun khi hoc x l nhit trckhi s dng v n c th cha ht c v cc loi nm c hi. Ct hu nh khng chacc cht dinh dng khong v khng c kh nng lm m. N c s dng hu htdng hn hp vi cc vt liu hu c.

2.5.2.3 Than bn (Peat)

Than bn bao gm nhng phn cn li ca cy mc di nc, m ly, t lyhoc ngp ng c bo qun di nc trong mt giai on phn hy c bit.

Thnh phn ca cc lp trm tch than bn khc nhau rt khc nhau ty thuc vo loicy ban u, giai on phn hy, thnh phn khong v acid.

C 3 loi than bn: than bn ru, lau lch v t nhiu mn.

Than bn ru (thng c ni n nh ru than bn trong thng mi) t bphn hy nht, c 3 loi v bt ngun t ru nc, hoc cc loi ru khc. N khcnhau v mu sc t nu nht n nu ti. N c kh nng gim cao (gp 10 ln trnglng kh ca n), acid cao (pH 3,8 4,5) V cha mt lng nh N (khong 1%)nhng t hoc khng c P hoc K. Loi than bn ny n t Canada hoc chu unhng mt sc sn xut cc bang pha Bc.

Than bn lau lch bao gm cc phn cn li ca c, lau, lch v cc loi cy ngpnc khc. Loi than bn ny khc nhau ng k v thnh phn v mu sc, t munu n en. pH t 4,5 7,0.

Than bn nhiu mn tnh trng phn hy rt lu n ni cc phn cn li cacy nguyn thy khng th xc nh c v c th c ngun gc t ru nc hocthan bn ca cy lau lch. N c mu nu ti n en vi kh nng gim thp nhngc 2,0 3,5% N .

Khi than bn ru c s dng vo hn hp, cn phi b nh v lm t trckhi cho vo hn hp. Tip tc thm cc nguyn liu hu cth nh than bn ru hoc

ru nc hn hp t trng trong nh knh c th lm gim kh nng lm m. Nc skhng thm mt cch d dng v nhiu phn tt s vn cn kh ngay c sau khiti nc. Khng c cch no tt trong vic ngn nga tnh trng ny, mc d cngdng lp i lp li ca cc tc nhn lm m thng mi c th thc y s thm nc.

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Hnh 2.34: Than bn va khai thc cha qua cngon xl v chbin

thnh cht trng

2.5.2.4 Ru nc

Ru nc thng mi l phn b non hoc phn sng b mt nc ca cc cysng m ly c tnh acid thuc ging Sphagnum nhS. papillosum, S. capillaceumv S. palustre. N v trng mt cch tng i, nh v c kh nng gi nc cao, nc th hp thu nc gp 10 20 ln trng lng ca n. M l v thn cy ru nc

gm phn ln cc nhm t bo gi nc. Nguyn liu ny thng c ct nh bngtay hoc bng my trc khi c s dng lm mi trng nhn ging. N cha tcht khong cho nn trong qu trnh pht trin ca cy cn phi b sung thm chtdinh dng. Ru nc c pH khong 3,5. N cha cht khng nm c hiu hoc chtc kh nng hn ch s ng nc ca cy con trng trong .

Hnh 2.35: Ru nc

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2.5.2.5 Cht khong bn cy (vermiculite)

y l cht khong mica m c th gin nng k khi bt nng. Nhng lptrm tch ln M c tm thy Montana v Bc Carolina. V mt ha hc, nl mt magnesium-aluminum-iron silicate khan. Khi gin n, n rt nh (9 14kg/m3),

trung ha trong phn ng vi c tnh m tt v khng tan trong nc; n c th hpthu mt lng nc 15lt/m3. Vermiculite c kh nng trao i cation tng i cao vv th c th gi li cht dinh dng v sau gii phng ra. N cha Mg v Kcung cp cho hu ht cc cy. Trong qung vermiculite th, cc phn t bao gm rtnhiu lp tch ring rt mng m gia chng c mt lng nc cc nhc gi li.Khi t vo l nhit gn 837oC, nc chuyn thnh hi lm tch ri cc lp, tothnh nhng ht nh ging nh bt bin, d thm. t nng nhit ny th n trnn v trng hon ton. Vermiculite dng trng cy c chia lm 4 kch c: s 1c ng knh cc ht t 5 8mm; s 2, loi thng c dng trong trng cy, t 2 3mmm; s 3 t 1 2mm; s 4, c cng dng lm mi trng gieo ht nht, t 0,75

1mm. Vermiculite nkhng nn n mnh hoc va p khi n t v nh th s lmph hy cu trc d thm nc mong mun ca n.

Vermiculite cha Cc ht vermiculiet Mt htvermiculite

gin n gin nHnh 2.36: Cc dng Vermiculite

2.5.2.6 trn chu (perlite)

Nguyn liu silica trng xm ny c ngun gc t ni la, c o t cc dngdung nham. Qung th c nghin nh v sng lc, sau t nng trong l khong760oC, nhit ny lng nc nh trong cc phn t chuyn thnh hi, lm gincc phn t thnh cc ht nh ging bt bin rt nh, nng ch (7 10kg/m3). Nhit

cao trong qu trnh ny to ra mt sn phm v trng. Mt ht c ng knh 3 6mmthng c dng trng cy. trn chu c th gic mt lng nc gp 3 4 ln trng lng ca n. V cbn n c th trung ha pH 6,0 8,0 nhng khngc kh nng lm m; khng ging vermiculite, n khng c kh nng trao i cationv khng c cha cht dinh dng khong. N c tc dng nht trong vic lm tng sthng kh trong hn hp.

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Hnh 2.37: Cc ht perlite

Hnh 2.38: Sn phm gi thtrng cy - peatmos, vermiculite v perlite

2.5.2.7 Phn trn (compost)

Hnh 2.39: Hn hp compost trn

perlite

Hnh 2.40: Compost qua

xl

Trong lm vn, hn hp phn trn c tc dng nh mt nguyn liu t nhiumn c kh nng gim v c gi tr gii hn nh mt cht dinh dng cho cy trng.

N c thc trn vi t c thm cht hu c. C ct nh, l v rc trong vnc cht ng v phn hy, tt nht l trong mt ci thng 1.2m x 1.8m vi ccmt c lm nh vt ging to s thong kh tt. Nn thm nc lin tc trongma kh; s phn hy s c y nhanh nu ti mt t phn m ln tng mnguyn liu c thm vo. Khi nguyn liu nn c o 5 10 ngy mt ln

m bo cho s phn hy c hon ton. Tt nht nn lm nhiu thng mt thngcho nguyn liu mi, mt thng nguyn liu ang c phn hy v mt thng cho

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phn phn hy hon ton sn sng dng. Phn ny c th cha ht c v giuntrn cng nh cc cn trng c hi v cc mm bnh, v vy tt nht l nn kh trngtrc khi dng.

2.5.2.8 V cy ct nh, mn ca, v bo g, v tru, xda...

Nhng nguyn liu ny bao gm cy g, cy tuyt tng cy linh sam hoc cythng c thc s dng trong hn hp t phc v cho nhiu mc ch ging nhaunh than bn ru ngoi tr tc phn hy ca chng chm hn. Nguyn liu c sdng rng ri l mn ca ca cy gc nitrate ha. Nitc thm vo mtlng cho yu cu ca s phn hy mn ca, cng thm mt lng d cho cy sdng. Tc phn hy khc nhau ty thuc vo loi g. V gi r nn n c sdng rng ri nh mt cht b sung cho t mc du mt s loi c bit khi cn tic th cha cc nguyn liu gy c cho cy. Cng c nhng loi gi th sn xut tiVit Nam gi r v d tm l v tru t, tro tru, than vn, thn cy dng x xay nh,dn mt hoc xda,..

V tru c th trn vi cc loi gi th khc nht mn, than bn,v.vcng rtthun li cho vic gim cnh.

Hnh 2.41: V ngo Hnh 2.42: V xda ct nh

Hnh 2.43: V tru Hnh 2.44: Bt xda x

l

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Hnh 2.45: V da cht nh Hnh 2.46: Than vn

Hnh 2.47: Cy d

ng xxay nh Hnh 2.48: Dn mt

2.5.2.9 Cc hn hp t lm gi th trng chu:

Trong qu trnh nhn ging, cy con hoc cnh gim thnh thong c trngtrc tip trong vn nhng thng chng c bt u trong mt hn hp t trongmt s loi bnh. V nhng nguyn nhn khc nhau, ring t nhiu mn khng thchhp cho mc ch ny. Chng thng nng v thong kh km, hoc c chiu hngtrnn dnh sau khi ti nc. Khi kh chng c th teo li hnh thnh mt b mtcng v d gy. t s bong ra khi cc mt bnh khi kh v sau nc c thmvo s chy xung theo cc mt bn trong ca bnh v ra ngoi qua cc l thot ncm khng ngm vo t.

cung cp hn hp trng cy c kt cu tt hn, ngi ta thng thm ct vmt s cht hu c nh than bn, ru, mn ca hoc v cy ct nh. Khi chun b

nhng hn hp ny, nn sng t lm cho n ng nht v loi b cc ht ln.Nu nguyn liu qu kh, nn lm m chng mt t. iu ny c p dng c biti vi than bn m nu trn kh th n s hp thu nc rt chm. Tuy nhin, khngnn t t v dnh. Khi trn, nhng thnh phn khc nhau c thc cho vong theo tng lp v trn bng mt ci xng. Mt ci my trn xi mng chy bngnng lng, my xn t hoc thng trn c s dng trong qu trnh sn xut quim ln. Vic chun b hn hp t tt nht nn tin hnh ti thiu mt ngy trc khis dng. Trong khong 24 gi, m c xu hng trnn cn bng trong ton hnhp. Hn hp t ch nn c lm m mt t khi s dng n khng vvn ra; nicch khc, ch nn lm t n lm thnh mt qu bng khi vo n trong tay. Mt

s phn kh nh vi ti v superphosphate c thc thm vo khi trn.

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Cc hn hp trng cy trong chu cin (truyn thng) c s dng trcy l:

o Dng cho trng cnh gim v cy con:1 hoc 2 phn ct

1 phn t nhiu mn

1 phn than bn ru (hoc v cy ct nh hoc mc l)

o Dng cho trng cy ging trong bnh:1 phn ct

2 phn t nhiu mn

1 phn than bn ru (hoc v cy ct nh hoc mc l)

Tuy nhin, cc tnh cht ha l ca hn hp khc nhau t m ny n m khc

nhiu n ni c nhiu vn pht sinh trong qu trnh chm sc v nui trng.Sau khi bt u cy mi bng to r cho cnh gim hoc gieo ht, nhiu nh sn

xut thng mi cy ging trng nhiu cy n mt knh thc c th bn c trongmt ci chu vi mt hn hp t ct c thay i. Nhng hn hp ny khc nhiuso vi ngnh cng nghip ny, nhng thng chng gm ct mn trn vi cc nguynliu nh than bn ru, mn ca ca g hoc v cy linh sam ct nh vi nhng t lkhc nhau. Nhng hn hp ny cn phi b sung thm phn v bn lin tc cho cycho n khi cy mc cnh.

Nhiu cng thc phi hp t trng nhn to c pht trin v s dng cho

cc vn m thng mi. V d, mt hn hp c s dng thnh cng cho cccy con vn m, cnh gim v cy trng lung gm cc thnh phn v cy linhsam ct nh, than bn mc vn m, trn chu v ct c phi hp vi mtt l cn bng. Hn hp ny c b sung thm thch cao, superphosphate, vidolomite v b tt. Thnh phn khong nitcung cp cho cy c b sung di dngnc ti.

2.5.2.10. Hn hp t trng U.C.

Cc nhm hn hp ny c pht trin u tin bi cc nh nghin cu bnh hccy trng v nhng ngi khc trng i hc California, Los Angeles cung cp

loi mi trng nui trng c thc pha ch sn vi s lng ln cho ngi mcy thng mi v cho chng trnh nhn ging v nui trng cy sch bnh. V hnhp U.C. cbn l cc nguyn liu ng nht, c sn v khng cn phi pha ch trccho nn chng c th d dng c nhn ln. Cc thnh phn cbn gm (a) mt loict mn tr, (b) ru than bn c ct nh c trn vi nhau theo nhng t l khcnhau v (c) cc hn hp phn bn nhc m tdi.

Ct gm cc ht trn, d b gi thi, ng nht v kch thc v tng i nh(ng knh 0,5 0,05mm), v th c kh nng gim kh cao. Loi ct ny khng cxu hng kt cht vi nhau cho d cc ht nh bi v chng c hnh dng trn v ngnht. Hn na, s vng mt ca cc ht t st keo dnh trong ct c xu hng ngn s

kt li v co li. Dnhin, ct bi bin c nng mui cao s khng thch hp cho

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hn hp t trng mc d cc loi ct thch hp c th thnh thong c tm thy chcch bbin khng xa lm.

Mc ch chnh ca than bn ru trong hn hp t ny l lm tng kh nnggim v cht dinh dng ca n. Trong mt hn hp c cc phn ct v than bn ru

cn bng th kh nng gim ti a khong 48%.Cc loi phn cbn c khuyn co cho thm vo mt hn hp U.C. c 50% ct

mn v 50% than bn ru nh sau:

1. Nu hn hp c bo qun trong mt thi gian khng hn nh trc khi sdng. Hn hp ny c ngun cung cp nitiu n nhng cy trng cn nhucu b sung thm cc nguyn t dinh dng. i vi mi m3 hn hp cn bsung thm cc thnh phn sau:

150g Nitrate kali

4kg vi dolomite

150g Sulfate Kali

1,3kg vi carbonate canxi

1,3 kg Superphosphate

2. Nu hn hp c dng trong vng mt tun sau khi chun b. Hn hp nycung cp nitdng c cng nh l mt ngun d tr nitiu n. i vimi m3 hn hp th thm:

- 1,3 kg bt xay th mng v sng hoc mu

- 1,3 kg superphosphate n (13% nit)- 150 g nitrate kali

- 4 kg vi dolomite

- 150 g sulfate kali

- 1,3 kg vi carbonate canxi

Nithu cb mt i nu hn hp c bo qun trong mt thi gian trc khi sdng, v nhiu dng hu cnh vy s b ph vtrong qu trnh bo qun, gii phngnc ha tan nitnng cao c th lm cho cy b thng. Cc dng khc ca nit

hu cnh bt xay th ht bng (7% nit) hoc xc c (6 10% nit) c th thay thcho bt xay mng v sng hoc mu m cng cung cp mt lng nittng ng.

Khi s dng hn hp U.C., ct mn, than bn ru ct nh v phn phi c trnu vi nhau. Than bn ru nn c lm m trc khi trn. Nu hn hp c lmtt, than bn ru s khng b tch ra v ni ln trn khi hn hp c bo ha vinc. Nhng s pha trn khc nhau ca ct v than bn c s dng; 75% ct v25% than bn ru th thch hp cho cy trng lung v cy ging trng trong chu;50% ct v 50% than bn th thch hp cho cy trng trong chu.

Hn hp ny, gm c phn, c thc tit trng mt cch an ton bng hi hoc

ha cht m khng c nh hng c hi n cy trng nh thng xy ra khi cc loit hoc hn hp khc c tit trng.

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2.5.2.11. Hn hp t John Innes

C 2 loi hn hp cbn, mt cho gieo ht v mt cho trng cy trong chu, c pht trin cch y nhiu nm Cquan nghin cu hoa qu John Innes Anh.

Phn trn ca John Innes gieo ht Phn trn ca John Innes trng cy

2 phn t nhiu mn (v th tch)

1 phn than bn ru (v th tch)

1 phn ct sch (v th tch)

i vi mi 1m3 hn hp ny trn thm

1,3 kg superphosphate v 0.7kg vinghin

7 phn t nhiu mn (v th tch)

3 phn than bn ru (v th tch)

2 phn ct sch (v th tch)

i vi mi 1m3 hn hp ny trn thm

3 kg hn hp c bn John Innes* v0,7kg vi nghin

* Hn hp John Innes cbn gm

2 phn v khi lng bt xay mng v sng,2 phn v khi lng vi superphosphate (18% acid phosphoric)

1 phn v khi lng sulfate kali (48% b tt)

t nhiu mn c s dng trong hn hp John Innes nn c tch ra t thanbn ng ct st, t chua, thot nc tt v ct thnh nhng mt ct 22 x 30cm, dy10 12cm. Hn hp ny c cht thnh ng vo cui ma xun vi nhng lp dykhong 22cm, mi lp c rc mt lp phn c rm dy 5cm v nu c yu cu ththm cc lp vi, sulfate kali v superphosphate. Cc lp c lm m tt trongqu trnh cht ng cho n khi hnh thnh mt ng cao 2m v rng 2 3m. ngny phi c che ma. S phn hy din ra trong khong 6 thng. Khi c th s dngc, ng c ct xuyn t trn xung di gim thiu s khc nhau. Trc khis dng t nhiu mn, nn cho n qua mt ci sng 1cm hoc mt ci my nghin.Ct c mong mun nht cho hn hp ny l loi m trong c 60 70% ht ckch thc 0,3 0,15cm. Trc khi lm hn hp phn trn, ring t nhiu mn nnc tit trng bng hi. Trong khi n cn c xem xt th t ly di c l mtthnh phn mong mun ca hn hp John Innes, cc nghin cu cho thy t tchtt b ha, phi trn th cng tt.

2.5.2.12. Hn hp "than bn - " Cornell

Nhng hn hp ny u tin c s dng cho vic gieo ht v trng trong chunhng cy trng lung vo ma xun v cy mt nm, dng cc thnh phn nh, ngnht v sn c v c tnh cht ha l thch hp cho s pht trin ca cy. Kt qu tuytvi t c vi nhng hn hp ny v cc hn hp pha ch sn c bn. Cchn hp loi ny c s thun li quan trng l khng cn kh tp nhim trc khi sdng.

Hn hp than bn loi A (dng cho 0,75 m3)

Than bn ru nc Canada hoc c ct nh 400lit

Vermiculite loi trng cy (s 2 hoc 4) 400lit

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vi nghin nh (tt nht l dolomite) 2.25 kg

Superphosphate (20%), tt nht l dng bt 0.45 kg

Phn 5105 (NPK) 5kg

Hn hp than bn loi B (tng t nh loi A, ngoi tr trn chu dng

trng cy c thay cho vermiculite)

Hn hp than bn loi C (dng gieo ht)

Than bn ru nc Canada hoc c ct nh 35 lit

Vermiculite loi trng cy s 4 (tinh) 35 lit

Ammonium nitrate 1 oz (4 phn mung canh)

Superphosphate (20%), dng bt 40 gam

vi nghin nh, dolomite 210 gam+ Nu 5.5 kg phn 5-10-5 c dng, n s cung cp cht dinh dng cho cy

trong vng 5 hoc 6 tun trong qu trnh pht trin. Nu lng phn thm vo t hn5.5 kg th nn c k hoch ti thm phn.

Nguyn liu nn c trn u, c bit ch cn lm t than bn ru trongkhi trn. Thm tc nhn lm t khng c ion nh Aqua-Gro (30g/ 25 lit nc) khilm t lc u s gip cho vic lm t than bn ru.

2.6. Cc h thng iu khin thng dng trong nh knh:

Trong phn ny, chng ti ch nu ln mt cch khi qut v cc h thng iukhin thng dng trong nh knh. Cc h thng iu khin trong nh knh bao gmcc h thng iu khin ch nh sng, nhit , m , h thng iu khin chgi trong nh knh. Cc h thng iu tit ny s h trcho nhau trong qu trnh hotng, v thng thng chng sc lp t ph hp vi cc h thng ph bntrong cu trc nh knh.

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Bi 3:

MI TRNG NH CHE PH

3.1. Cc yu t mi trng trong nh che ph:iu kin mi trng trong nh che ph bao gm cc yu t chnh nh nhit

, m, nh sng, v thng thong. Ngoi ra cy trng cn chu nh hng cacc tnh cht ca gi th v cc t chc hu ckhc.

3.1.1. Nhit :

y l mt yu t rt quan trng i vi s pht trin ca cy trng. Do hthng nh knh tng i cch ly vi mi trng xung quanh, nn nhit trongnh knh c th khc so vi iu kin bn ngoi. Nhit trong nh knh thng caohn nhit bn ngoi.

3.1.2. m :

L mt yu t quan trng th hai sau nhit . N bao gm m khng kh vm gi th trng. m trong nh knh thng cao hn mi trng bn ngoi, l iu kin tt cho s pht sinh xm nhim ca cc vi sinh vt, c bit l nm, vikhun. Do cn iu khin m trong nh knh cho thch hp vi tng loi cytrng m vn hn ch s pht sinh ca nm bnh.

3.1.3. nh sng:

y l yu t rt quan trng cho qu trnh quang hp ca cy trng, l yu t

lin quan n nng sut sn xut ca cy trng cng nh hiu qu sn xut ca cc nhu t. nh sng l yu t c lin qua trc tip vi nhit ca nh knh. Trongnhng ngy nng gt, nu nh knh khng c h thng thng kh tt s d gy nn hiung nh knh. Lc ny do ngun nng lng chiu vo nh knh ln, cy trng khngc kh nng hp th ht lng bc x ny v cc bc x phn x tr li bng ngunnng lng c bc sng di cy trng khng s dng. Ngun nng lng ny stnng trli i vi bu kh quyn bn trong nh knh v gy nn hiu ng nh knh.

3.1.4. Tc gi:

Tc gi cng nh thng thong ca nh knh l yu tm bo cho s

lu thng khng kh iu ho gia cc lung cy trng trong nh knh cng nh gianh knh vi mi trng xung quanh.

3.1.5. Ch nc:

Ch nc ca cc h thng ti nc trong nh knh c lin quan rt ln nm t v m khng kh, v c nhit ca mi trng

Ngoi ra cy trng cn chu nh hng ca cc yu t v mt tnh cht l, ho,chc ca t, dinh dng v s xm nhim ca cc vi sinh vt cng nh cn trnggy bnh.

Ch nc trong nh knh c thc cung cp v iu chnh bng cc hthng ti, h thng cp v thot nc c lp t trong nh knh.

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3.2. Cc h thng iu khin v cch iu khin mi trng trong nh che ph:Mi loi cy trng i hi vi nhng iu kin khc nhau, do cn thay i

cc yu t mi trng cho ph hp vi tng loi cy cng nh tng loi nh knh khcnhau. iu khin mi trng trong nh knh cn phi c s h trca cc h thngnh: h thng thng gi, h thng iu ho nhit, h hng phun sng, hi nc,.. vmt s yu tiu khin lin quan n vt liu xy dng nh knh.3.2.1. iu khin nhit :

y l vn ng quan tm nht i vi nhiu nh lm vn, v nng lngmt tri pht ra gia ma xun v ma thu l rt thng xuyn v vt qu nhu cucn chiu sng hng ngy ca cy. Nh vy cn thit phi c s trao i kh mt cchthng xuyn gi cho nhit khng kh mt mc ph hp cho s sinh trngca cy trng. Khi tng nng lng mt tri c bc sng ngn m cy trng trongnh knh nhn c, ch khong 3/4 lng bc x l cy hp thu v 1/4 phn x trli trong nh knh di dng nh sng khuych tn c bc sng di hn. V cc vtth khc trong nh knh lm phn chiu nng lng mt tri, ch hp thu mt phnnh, nn chnh l nguyn nhn lm gia tng nhit trn b mt l v xung quanhcc vng trong nh knh. ci thin hn ch s gia tng nhit, bng cch lm gimlng nhit sinh ra nhqu trnh thot hi nc, to ra trong qu trnh trao i kh.Tng lng din tch l ca bt k loi cy no trong nh knh cng cn phi xem xt,v chng c nh hng ln n t l nh sng hp thu v nh sng tn x trong nhknh v thay i qu trnh trao i kh din ra trong nh knh. Trong cng mt nhknh, nu tng din tch l cng cao (ch tnh din tch l c kh nng quang hp) thtc nng ln ca khng kh bn trong nh knh cng gim. Chnh v vy, vic b trcy trng v cc lung cy trng trong nh knh cng cn phi c tnh ton mt cchthch hp.

V khng kh, lc nng ln, th mt t dy c hn, v nng ln, v th cnphi c s thng thong nhng v tr cao nht dc theo cc lung cy. Khng khlnh cng c i vo thng qua l thot tng t nh vy bng my thng gi phctp, vi iu kin l c khng kh thot ra ngoi c sc y cho s thay ikh ny. Nu vy khng kh lnh cho php i vo cc l thng hi bn di s thcy cho c qu trnh lu thng ny.

Hnh 3.1:ng lu thng khng kh trong nh knh

Nhit ngy trong nh knh thng cao hn ban m. nc ngoi, vic

iu ho nhit (ma ng) thng chim chi ph cao sau cng lao ng. Thngthng, tu theo yu cu nhit ca tng loi cy trng, tuy nhin nhn chung trong

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nh knh nhit thng c duy tr khong 18-25oC l thch hp cho hu ht ccloi cy (ban ngy), v vm thp hn 5-6oC l tt.3.2.1.1. Kch thc v cch b tr cc thot kh (ventilator):

Thng thng cc thot kh ngi ta thng b tr pha trn mi nh knh. S

lng cng nh kch thc ca s thng gi ny ph thuc vo din tch kt cu kiunh knh v s lng, cng sut ca cc h thng qut gi bn trong nh knh. i vinh knh kiu ch A, ngi ta b tr cc ca s thng gi pha trn mi ch A, vcng c th b tr pha hng ca nh che ph hay nh knh. Tuy nhin, nn b tr ccca thng gi pha trn cao trnh c cn trng v cng khng nn b tr ti ninh sng mt tri c th trc tip i vo trong nh knh, v nh th s lm cho lngnh sng chiu vo nh knh khng ng u c thnh hng n qu trnh quanghp cy trng v kh nng iu ho ca cc h thng iu ho nhit, iu ho khngkh trong nh knh. Hin nay ngi ta cn s dng loi ca thot kh tng b trlp t trong nh knh. Mt vi loi nh che ph, nh knh ngi ta lp t hcao thp

2 na mi vm nh knh cha li khong trng pha trn nc mi nh knh, ycng c xem nh l mt h thng ca thot kh ca nh knh. Loi ca thng giny thng thy loi nh knh kiu ch A c lp hoc lin hp v loi nh vm h.

Vic thit k cho nh knh cc thot kh trn mi mt cch hp l l iu rtquan trng. i vi nhng nh knh c kch thc rng trn 6m, th thng thch hpvi loi thng lin tip trn c hai bn ca mi che. i vi nhng nh knh c kchthc nh hn c cu trc khng in hnh (cc dng nh mi che nh dng cu trctp) th dng thng gi lin tip khng cn thch hp na, lc ny ngi ta thngthit k cc gi xen k (Alternate ridge Ventilators). Trong trng hp ny, th gi sthi vo mt bn v chuyn ra ngoi thng qua cc gi mi i din. Cn ch

rng m bo thng thong mt cch tt nht th tng din tch cc gi phi tnht bng 1/5 n 1/6 din tch sn nh.

Hnh 3.2. : Cch btr gi lin tip v gi xen k.

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Hnh 3.3: Cc kiu gi chnh thng dng

3.2.1.2. Qut gi v cch iu khin nhit bng h thng qut gi:

Cn thit c mt phng tin em li s lu thng kh v s trao i kh trongtt c cc nh knh gip kim sot nhit v m. Hu ht l s dng my thnggi trn nc nh, mt s trng hp cng s dng my thng gi bn hng. Cc b

phn kim sot hot ng mt cch tng v chu nhit lun sn sng mv ngmy thng gi khi c s thay i nhit c ngy v m. S thong kh bt bucthng c s dng trong nhng lp t trn phm vi ln. S dng my thng kh tmv h thng lm mt hi nc c kim sot bng biu nhit tng. Quy lutchung l khi nhit ban m xung 15,5oC th biu nhit lm nng c bt ln. nhit khong 22oC th biu nhit ca my thng gi c mv 24oC th

biu nhit ca my lm lnh bng hi nc bt u khi ng my qut gi. mtvi h thng nh knh, nh che ph ni tip, h thng thng gi thng c lp t cui chuyn tip ca tng gian v hi m c y bi h thng qut thi nhm

phn phi iu tit nhit i khp nh knh.

3.2.2. H nhit trong nh knh nh che ph:

Vo nhng ngy nng gt, nhit khng kh trong nh knh thng thng tngln cao so vi bn ngoi, do nhit tng cao, vic di chuyn trao i ca khng kh

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trong nh knh trnn hn ch v chm chp. Nhit nng nhng ngy nng gt c thln n 17.000kJ/m2/ngy. Do cn h nhit ca mi trng trong nh knh cho

ph hp vi cy trng.- Nh knh c thc lm mt mt cch my mc vo ma h vi gi thp

bng vic s dng nhng b phn lm lnh bng hi nc. H thng m v qut ,trong mt tm m t bng mt s cht liu nh v bo g dng bao gm mt

phn ln nm mt mt (hoc phn cui) ca nh knh v nhng ci qut ht ln mt kia, l mt trong nhng phng php lm lnh tt nht cho nhng nh knhln.

- lm lnh nhit trong nh knh, ngi ta thng lm tng lu thnglng khng kh bng cch kt hp cc h thng qut gi, h thng ti phun sngv cc thng thong ca nh knh.

Nh vy, c 2 phng php h nhit cho nh knh: lm m khng kh v thngthong gi.

3.2.2.1 Lm m khng kh

Lm m khng kh trong nh knh bng cch lm gim lng nhit do nh sngmt tri t nng. Dng h thng ti nc mn, phun sng (4000-8000kPa) ciu khin bng ng h hn gi lm m, gim nhit trong nh knh.

Hi bc t ht nc mn, sng s lm mt khng kh, ngoi ra h thng nycn lm tng m tng i ca khng kh v rt c ch cho cy con mi trng, cygieo ht, cy m nhn ging,...Tuy nhin s dng h thng ny cn ch hin tngnc ng nhiu trn b mt l cy.

3.2.2.2 Thng gi trong nh knhy l phng php lm mt nh knh bng cch lm tng tc trao i kh

vi mi trng bn ngoi, lm di chuyn khng kh bn ngoi vo trong nh knh. C3 cch thng gi cho nh knh:

o Thng gi bng mi v bn hng nh (convective cooling by anh/or sideverticalation)

Khng kh c ht vo nh v to nn s lu thng khng kh v lm mt nhknh.

Ngi ta cn to cho mi thng gi c th di ng c thiu chnh hng gi ttnht thi vo nh (vi loi ny ngi ta dng motour ko mi, mv ng)

o Thng gi bng qut ht v ca s tng:Loi ny thng c s dng i vi nh vm hoc nh khng c nc h. Gi

c lu thng bng mt qut gi ln c t mt bn vch, nm pha cui nhknh. Nhim v ca qut l ht gi t bn ngoi vo nh. Qut c t v tr cchmt t chng 0,5-1,5m ty thuc vo loi cy trng.

Thng thng dng qut c cng sut ln, ng knh cnh qut t 0,6 - 1,4 m,tc chm nhng c kh nng lm di chuyn lng khng kh (m3) ln.

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Ca tng c gn lin vi qut (v d qut thng gi t nh). Thngthng, s trao i khng kh thng qua qut v ca s t ng c cng xut ln(2,5m3/m2 sn nh/pht).

Trong trng hp cn, c tht 2 qut hoc nhiu hn. Khi khong cch

thit k qut gi l 8m (qut x qut) to ra s di chuyn ng u khng kh trongnh knh.

Thng thng qut gi c thit kcui nh, ht khng kh dc theo nhv lm thong lung trng.

di ht khng kh ca qut t 65m tr li. Do nu khong cch ln hn65m th s lm cho khng kh bn trong nh knh khng u, c ngha l c vng nngc vng mt.

i vi mt s cy trng c nhu cu nhit thp hn trong ma h, ngi ta cnthit k mt h thng lm bc hi kh lnh v c t u nh knh, v tr c ca s

thng gi.o Thng gi bng h thng qut p gi (fan-jet system)

H thng ny gm mt qut thi gi, v mt h thng ng thng hi bng PE,v mt ca s thng gi.

Cng sut qut tng ng vi 0.4-0.6m3/m2 sn nh/pht.

Gi bn ngoi c ht bi qut, qua ca s tng (c h thng tiu khinnhit v m ). Sau khng kh c y i dc theo ng ng v thot quacc lc c sn trn ng. u cui ca ng ny c bt kn.

Qut gi thng thng hot ng 24h/ngy v cng thng t cui nh knh lm thng thong khng kh trong nh v trong cc lung cy.

i lc i vi nh knh nh ngi ta cn to ra mt s di chuyn khng khcng mnh cng tt bng cch s dng nhng qut ht gi.

3.2.3. iu khin h thng lm nng:

Vo ma ng khi nhit thp, hoc khi nhit khng kh lu thng trongnh knh gim xung mt cch t ngt d gy nh hng n sinh trng v phttrin ca cy trng. Chnh v th trong nhiu trng hp chng ta cn phi iu titsi m khng kh trong nh knh.

Hin nay i vi loi nh knh c kch thc nh, ngi ta s dng ph binloi my sy Jemp si m nh knh.

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Hnh 3.4: My sy in Jemp

Nh knh cin c si m bng hi nc hoc nc nng t cc bnh un

nc cho qua cc ng ng (mt s c ra c s dng tng b mt ta nhit)c t ni thch hp trong nh knh. Tuy nhin, nhng b phn si m c qut y mnh s tun hon kh. Nu b phn si m chy bng du hoc gas th bt buc

phi ml thng ra bn ngoi v cc sn phm t chy gy c cho cy trng. Nhit trong ng c th ln ti 110-120oC. Khng kh nng thng bc ln cao, do mng ng nc nng c thng t pha di mt t. Chi ph s dng nc nngr tin hn s dng hi nng.

Hnh 3.5: Hai h thngt nng bng du.

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Hnh 3.6: H thngt sim Hnh 3.7:ngng to nhit c bra.

nhng nh knh rng, c th lp t h thng ng thot kh lm nng chonh knh. Kh nng thi vo nhng ng polyethylen c ng knh rt ln 30 60cmc treo trn cao v chy dc theo chiu di ca nh knh. Nhng l nh trn thnng c ng knh khong 5 7cm cho php kh nng thot ra lm cho c phng um ln. Nhng ng tng t c thc dng cho thong kh vo ma h m khngcn my mc v nhng l trn nh.

Hnh 3.8: H thng sim bng nhit Hnh 3.9: Slun chuyn ca nhitpht ra th thng sim

3.2.4 Lun lu khng kh trong nh knh:(air circulation)

Lun lu khng kh trong nh knh l rt quan trng v cn thit i vi cytrng: iu ho nhit , m , (k c lng O2 v CO2 cho cy trng)

Thng thng ngi ta dng qut gi (HAF: Horizontal Air Flow) c ngknh t 30-45cm, cng sut ch khong 25-50 /gi. Cc loi qut ny c th to svn chuyn khng kh t 10-12m/pht.

Qut ny c thit k to s vn chuyn khng kh theo chiu dc ca nhknh.

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Nhn chung, vic lun lu khng kh trong nh knh c chc nng nh sau:

- To ra sng u vm khp nh knh.

- To m tng i u (RH%)

- Phn bu kh CO2

trong nh knh.

- Gim thiu mt s bnh trn l nh phn trng, thi nhn, mc sng,...

- Tng kh nng bi tit ca cy trng (H2O), lm tng kh nng quang hp, gipcy trng hp ph nhiu hn H2O v dinh dng t r.

- Tng kh nng trao i kh cho cy trng.

C 3 phng php lm lun lu gi trong nh knh:

Vertical delivery fans: (qut theo chiu ng)

Qut gi c treo trn trn ca nh knh, v chng s gip di chuyn khng

kh m xung cy trng. Phng php ny khng to sng u, khng hiu qu lmnn thng ch s dng i vi cc nh knh c din tch rt nh.

H thngng qut thng gi (Fan tube system)

Gi, khng kh sc lun lu trong ng nha c c l, v khng kh cthot ra qua cc l nh ny. H thng ng nha s dng trong trng hp ny c nhiukch c khc nhau, thng thng c ng knh t 40 70cm. Cc l thot kh cng knh khong 5 8cm c c thnh hng hai bn ng vi khong cch giacc l t 0,5 1,0m.

Lun lu khng kh theo chiu ngang (Horizontal Air Flow).

y l phng php hiu qu hn, khng kh c phn bu hn v t tnkm hn so vi phng php qut dc.Qut c t i ngc chiu, v b tr theo hng to ra mt lung gi xoy theochiu ngang.

3.2.5 H thng ti:

H thng ti y ca mt nh knh s gm c nhng phn sau: H thnglc, h thng bm, h thng ti nh git cho nh knh, h thng lm mt cho nhknh, h thng ng chnh, ng nhnh v ph kin. Ngoi ra cn c bn cha nc, hthng ti phn, h thng ng h tr chy quanh b tr trong nh knh. V h thngti ny cn c mt phng iu khin ch ti.

Trong , h thng bm sc t trong nh iu khin ti v bao gm: Mtkhung gi bo v bng thp, mt bm cho h thng trn phn bn, mt bm cho hthng lm mt nh knh v mt my bm cho h thng ti nh git.

3.2.6 H thng chiu sng trong nh knh:m bo cung cp y nh sng cho cy trng trong nh knh vo ma

ma, ngi ta thng lp t h thng n in trong nh knh. Thng th h thng

ny c thiu khin bng rle t ngt (loi t ngt c hn gi).

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Hnh 3.10: Btr h thng chiu sng

Hnh 3.11: H thngn chiu sng

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Bi 4BO DNG NH CHE PH

4.1. Scn thit ca vic bo dng nh che ph:

Cc loi nh che ph, sau mt thi gian s dng thng gp phi nhng trctrc no . Cc nh che ph, nh knh thng c xy dng ngoi tri. Do chngphi tri chu s bin i t ngt ca cc iu kin kh hu nng ma gi bo,.. Mtkhc, tt c cc h thng iu ho mi trng trong nh knh sau mt thi gian hotng c th gp phi nhng hng hc. Do vy, ko di tui th nh knh nh che

ph, th nht thit phi c nhng phng php bo dng thch hp.

4.2. Cc nguyn nhn gy hhng nh knh:

4.2.1. Hhng do cc yu t thi tit:

y l yu t ch yu gy h hng cho nh knh nh che ph. Nh knh c

xy dng ngoi tri, nn kh hu thi tit l yu tu tin tc ng mnh nht gyh hng cc b phn ca nh knh.

4.2.2. Hhng do sph hoi ca cc vi sinh vt.

Trong qu trnh s dng do cc iu kin kh hu kt hp vi bi bn bm trnknh thch hp cho s pht sinh v pht trin ca cc vi sinh vt nh m ch yu l ccloi nm mc. Chng bm trn knh v lm cho tm knh mdn i theo thi gian.Chnh v vy lm gim kh nng nhn nh sng ca nh knh.

Cc b phn khc ca nh knh cng c th b gy hi bi cc loi nm, to.m cao trong mi trng nh che ph chnh l iu kin thun li cho s pht sinhv gy hi ca cc loi vi sinh vt ny. Chng pht trin hu ht trn tt c cc b phn

bn trong cng nh bn ngoi nh che ph. Chng c th gy hi lm mc nt cc bphn bng g hoc lm tng qu trnh oxy ha cc vt liu bng kim loi. Chnh v vyy l mt trong nhng tc nhn gy hi quan trng i vi nh che ph nh knh.

4.2.3. Hhng do cn trng v cc sinh vt khc cn ph: loi ny ch yu i vinh che plastic.

4.2.4. Hhng cc h thng iu tit mi trng:

Do s dng khng hp l hoc do bt cn trong qu trnh iu khin gy nn

nhng tn tht h hi cc linh kin ca h thng. Mt khc, cc h thng iu khintrong nh che ph sau mt thi gian s dng c th gp phi nhng trngi.

4.3. Cc bin php khc phc v bo dng nh knh nh che ph:

Mt trong nhng bin php nhm tng tui th ca nh knh l s dng sn.Quy trnh sn nh knh cng nh cc loi sn/vi v mc sn thng xuyn cng c cp n. Yu cu hin nay l xy dng mt nh knh khng cn hoc cnrt t s bo tr bi v khng c g rc ri hn vic lin tc phi lo lng n vic bo trnh knh.

Bi bn bm vo to thnh mt lp bn dnh v theo thi gian mt lp bi s

hnh thnh trn knh, hn ch s truyn nh sng mt cch ng k. Ru v to phttrin trn b mt knh v trn nhng thanh lp knh. C lc v to cng vn c th

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pht trin di bar-cap nu m t ti mc thch hp, m thng th chuyn ny dxy ra. S pht trin ca ru v to, c bit l ru rt c hi, chng c th s lm chocc mi gn gia cc thanh b khung v phn knh. Trong trng hp ny chng ta cth tin hnh vic lau ra knh bng cc nc ra knh ph hp hoc cc tinh th axitoxalic ho tan trong nc, 100g trong 1lt xt ln v ra sch, phng php th 2 nyc bit cn thit i vi nh knh bng kim loi. Axit oxalic cng s thiu hy mt tl kh ln ru, phn cn li s b ra tri bi vi phun nc mnh. Ru v to cng

pht trin bn trong nh knh, tt hn ht l nn tin hnh vic dn sch chng khi nhknh khng c cy trng.

Nn mc bo h v i m chng thm trong sut qu trnh dn dp nhknh. Axit crezola hay cc loi dung dch ra knh thng dng khc rt c hiu qu chovic lm sch bn trong nh knh bi v chng c kh nng lm sch ru v to rt hiuqu. Ru v to ch knh ph nhau nn c dn sch bng mt mu kim loi v vinc.

Mt trong nhng vic phng quan tm vi bt k loi nh knh no l ssch s ca knh, c bit l trong nhng khu cng nghip, nhng khu vc nhiu bi

bn.

Chn tng nn c ch sch mi nm vi mt bn ch bng st; nu cn thitth qut vi trng hoc dng sn nh tng.

i vi nh che ph, sau mt thi gian s dng, th nylon mt kh nng chonh sng, do cn thit phi thay mi.

Cc h thng s dng trong nh knh phi thng xuyn c kim tra v lauchi.

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Thut ngchuyn mn

Ridge: l nh nc ca nh che ph.

Vertilator: l thng gi

Eaves: mi hinPurlin: (n tay) l b phn lp trn mi, dc theo chiu di ca nh knh

Sill: ngng ca

Chords: giy cn

Strut: thanh chng

Rafter: rui

Sidewall: vch bn

Sidepost (Anchor support posts): tr bn, l cu trc chng ch yu ca nhknh.

Curtain wall: vch chn

Ground level: mt t

Footer: chn (mng)

Even-span: nh c mi i xng ch A

Uneven-span: loi nh c mi khng i xng

Lean-to: loi nh knh ta vch

Quonset: dng vm chp

Gothic arch: dng chp

Curvilinear: dng hnh cong

Curved eave: dng hnh cong c mi hin.

Dome: dng vm

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TI LIU THAM KHO

- K thut lm vn, 2000. Hong c Phng, NXB Nng nghip.

- Floriculture principle and speceies, Nohn M. Dole anh Harold F. Wilkins. Prentice Hall Inc. 1999.

- Practical Horticulture .4th ed. 1999. Laura Williams Rice, et al; Prentice Hall PTR.408pp. 0130206105.

- Greenhouse Management a guide to structure enviromental control, materialshandling, crop programming and business analysis. Langhans, R. W. 1980. HalcyonPress of Ithaca. New York.

- Bridwell, Ferrell M.,Landscape Plants, Delmar Publishers, Inc., Albany, NY, 1994.