32(1), 79 86 Tap chi CAC KHOA HOC vg TRAI BAT 3 2010 THOAI HOA DAT VA QUA TRINH HOANG MAC HOA 6 VUNG NAM TRUNG BO NGUYEN DINH KY, NGUYEN LAP DAN, NGUYfiN MANH HA I DAT VAN DE Trong Cgng udc chd''''ng sa[.]
Trang 132(1), 79-86 Tap chi CAC KHOA HOC v g T R A I BAT 3-2010
THOAI HOA DAT VA QUA TRINH HOANG MAC
HOA 6 VUNG NAM TRUNG BO
NGUYEN DINH KY, NGUYEN LAP DAN,
NGUYfiN MANH HA
I DAT VAN DE Trong Cgng udc chd'ng sa mac hda cila Lien
hgp qudc (UNCCD) ky thang 6 nam 1992 tai hdi
nghj thuong dinh Rio de Janero da khdng djnh "sa
mac hda - la su suy thoai ddt dai tai cdc viing khd
han, ban khd han, ban dm khd han, hinh thdnh do cdc
yiu td khac nhau bao gdm sir biln ddi khi hau va
cac hoat ddng cila con ngudi Suy thoai ddt la su
suy giam hoac mdt nang sudt sinh hgc vd kinh t l
cila ddt trdng trgt sii dung nudc mua, ddt trdng trgt
sii dung thiiy lgi, hoae bai chan tha gia sue, ddng
cd, rtrng va ddt rtrng " {7 ] Nhu vay thoai hda ddt
va hoang mac hda cd quan he nhan qua khang khit
trong tu nhien, thi hien d sir chuyin hda ttr ddt
nguyen sinh - ddt thoai hda - ddt hoang mac hda
Chuong trinh hanh dgng thuc hien cdng udc hoang
mac hda eiia Thil tudng Chinh phu Viet Nam eiing
khdng djnh : d Viet Nam, chd'ng sa mac hda Id ngan
chan, han ehi qua trinh thodi hda ddt d vung ban
khd han, khd han Vimg Nam Trung bg dugc coi la
vting trgng dilm phdng chdng hoang mac hda (7)
Dilu kien phat sinh ddt vung Nam Trung Bg (ttr
Da Ndng din Binh Thuta) thudc nhiet ddi gid mua,
cd mua khd kha dai (6-9 thang) Viing Ninh Thuta
- Binh Thuta ed mtia khd dai 8 - 9 thang, tuong
iing vdi cting ban khd han Dien tich ddt cila viing
tren 43.000 km^ Cdu triic ldp phii thd nhudng da
dang phirc tap vdi 10 nhdm, 20 loai vd tren 65.000
ha niii da, tren 265.000 ha cdn cat va bai cat Qua
trinh thoai hda ddt d vting Nam Trung Bd ciing da
dang, phiic tap vd vdi cudng dg manh me, ddn din
nhilu loai hinh hoang mac hda khac nhau Su thiet
hai do thoai hda ddt va hoang mac hda trong phat
tril'n kinh t l - xa hdi cila vimg Nam Trung Bd la rdt
ldn, eta dugc nghien cim dl han chi, ngan chan {1)
Tren quan dilm tdng hgp dja ly phat sinh va
thoai hda ddt ddn din hoang mac hda d vting Nam
Trung Bd, cac kit qua da chimg minh thiic trang thoai hda da't dan din hoang mac hda cila khu vuc Ddng thdi xdc djnh cac tinh ehdt, nguyen nhan can ban ddn de'n hoang mac hda
II KET QUA NGHIEN ClTU VA THAO LUAN
1 Dieu kien hinh thanh va cic qua trinh thoai hda d&'t vung Nam Trung Bp
a) Dieu kien hinh thanh dat
Viing duyen hai Nam Trung Bd Viet Nam bdt ddu ttr deo Hai Van (vy dd 15°30' B) din Nam huyen Ham Tan tinh Binh Thuta (vy dg 10°34' B) bao gdm eac tinh Da Ndng, Quang Nam, Quang Ngai, Binh Djnh, Phil Yen, Khanh Hda, Ninh Thuta, Binh Thuta Dja thi tir nhien khdi quat ciia vting la noi tuong tac giiia sudn Ddng cila Trudng Son Nam vdi Biln Ddng Cdc ddng bang duyen hai nhd hep hinh thdnh do kit qua tuong tac lau dai va phirc tap dd
Dilu kien sinh khi hau thd nhudng cila viing nam trgn trong vting nhiet ddi gid mua, vdi sir phan hda
rd ret hai miia khd vd mua Ddt phat sinh mang tinh dia ddi phd biln la vang dd, vang xam Tdng nang lugng biic xa Mat Trdi trong vting Idn hon 150-160 kcal/cmVnam vd tdng nhiet dd tren 10 °C, trung binh tren 8.000-9.000 °C, nhiet dg trung binh hang nam tren 24 °C Sir khac biet nhiet dg cac thang trong nam khdng dang kl Lugng mua trung binh nam ciia vung tren 1.500 mm song tap trung 75-90 % vao mua mua ttr thang 5-6 din thang 10-11 Trong viing cd hai trung tam mua ldn tren dudi 3.000 mm
la Trd Mi - Ba To (Quang Ngai), Diic Linh - Tanh Linh (Binh Thuta) Mua khd keo dai 6-9 thang Dac biet khu vue ttr Ninh Son - Ninh Hai (Ninh Thuta) de'n Tuy Phong - Bdc Binh (Binh Thuta) la mgt trung tam khd han vdi lugng mua trung binh nam 500-700 mm (cd khi xud'ng dudi 500 mm) Quy luat
Trang 2phdn hda mua theo dd cao dja hinh thi hien: khu vuc
ddng bdng ven bil'n (dac biet vung cat) lugng mua
trung binh thdp, khu vuc chan niii lugng mua trung
binh tang len, vting niii dat hon 1.500-2.000 mm/nam
Trong khi dd kha nang bd'c hoi cila khu vuc thudng
xuyen len din tren 1.300-1.400 mm/nam Vung ven
biln lugng mua thdp, kha nang bdc hoi ldn gdp 2-31
ldn lugng mua Chinh vi vay da tao ndn mdt vting
ban khd han diin hinh d Viet Nam Lu lut va han
kiet thudng xuyen xudt hien trong vting
Dja hinh sudn Ddng Trudng Son ddi nui dd'c
chia cdt tren 80 % dien tich tir nhien Dg cao tuyet
ddi nhilu dinh tren 1.000 m, dil dilu kien de xudt
hien ddt mim vang dd tren niii Tinh tuong phan dia
hinh giQa ddi niii va ddng bang da tao ra tiim nang
xdi mdn ldn Dai ddi them tilp giap vdi ddng bdng,
noi chuyin tai nudc ttr sudn Trudng Son nen qua
trinh nia trOi manh vd qua trinh laterit hda phat triin
xudt hien ddt xam bac mdu (61
Sdng ngdi vung duydn hai Nam Trung Bg deu
ngdn, dd'c, hep, bung chira nudc nhd Ciia song bi
che chdn bdi cac dai cdn cat ven bien va cac ddy nui
dam ngang ra bien nen khd tieu thoat nudc vao mtia
lu Mua khd nhieu sdng sudi bj bdi ldp ldng sdng va
can nudc Hdu hit phii sa ctia cac sdng tao nen ddng
bang diu cd thanh phdn co gidi nhe ttr ddt phii sa
ddng bang Tuy Hda cila sdng Ba chdy qua vting cao
nguyen basalt
Ldp phil thuc vat trong vimg phan hda ro ret theo
dilu kien khi hau thd nhudng ttr bac vao nam va ttr
ddng sang tay Ttr Quang Nam - Da Nang din Nha
Trang phd biln la rtrng kin thudng xanh nhiet ddi,
cdn Nha Trang din Phan Thilt xudt hien kilu rtrng
nhiet ddi rung la (rtrng khdp) Rimg rung la chi thj cho dilu kien khd han Ttr ddng sang tay cd thi gap cac tham thuc vat rimg ngap man din cac trang trudng cay gai, xuong rdng trdn da't cat, rtrng rung la tren dd't xam bac mdu, vting ddi thim vd tren niii la rtrng kin thudng xanh Dang chii y la trong vung cd tren 65.000 ha niii da trgc vdi cay bui gai, hd'c da va han 44.000 ha cdn cat bd hoang trd'ng cd thdp, xuong rdng Lich sir khai thac dd't ciia vung da trai qua phuang thirc du canh dd't nuong lam rdy va chan tha dai gia site lau ddi ciia dan tde Cham Do thuta tien giao thdng nen rung va ddt rung d day dugc khai thac sdm Quanh cac khu vuc thap Cham tinh trang thoai hda ddt va khd han diin ra manh nhdt Ngoai ra cac cudc chie'n tranh keo dai ttr xa xua din nam 1975 cung la mdt trong nhirng nguydn nhan ctia tinh trang thoai hda da't va hoang mac hda 12]
Tir cac dilu kidn phat sinh ddt da hinh thanh nen ldp phil thd nhuong vung duyen hai Nam Trung Bd thi hien tinh da dang phirc tap Hdu hit cdc nhdm ddt
ctia ca nudc diu cd mat d trong vting {bdng 1 va 2)
So sanh cac nhdm ddt tren cho thdy : nhdm ddt man va ddt phen cd dien tich nhd nhdt, chilm 1,31% dien tich viing, tuy vting nghien cim cd bd biln keo ddi tren 700 km Nhdm da't cat va cdn cat trong vting chie'm gdn 50 % dien tich loai ddt ca nudc Nhdm ddt nau vung ban khd han tuy chilm 0,97 % dien tich vung song la don vj phat sinh dac thu chi xudt hien d Ninh Thuta, Binh Thuta Cd the coi day la ddu hieu chi thj cho kha nang xudt hien hoang mac hda Nhdm ddt xdi mdn tro sdi da cung chilm ty le cao so vdi loai ddt ca nudc (gdn 10 %) Chilm dien tich ldn nhdt la nhdm da't xam (78,39 % dien tich
Bdng 1 Dien tich cac nhom da't vung duyen hai Nam Trung Bo
Nhdm ddt
Cdn cat vd ddt cat ven biln
Da't man
Ddt phen
Ddt phti sa
Ddt Idy 4- ddt giay chua
Ddt den
Dd't nau vting ban khd han
Ddt xam
Dd't dd
Ddt xdi mdn tro sdi da
Tdng cdng
Dien tich ca nudc (ha) 533.434 971.356 1.863.128 3.400.059 452.418 112.939 42.330 19.970.642 3.014.594 495.727 30.856.627
Duyen Dien tich (ha) 265.175 49.560 7.589 317.989 103.943 22.241 42.330 3.417.782 86.632 46.628 4.359.869
hai Nam Trung Bd Phdn tram so vdi loai ddt ca nudc 49,71 5,10 0,41 9,35 22,97 19,69 100,00 17,11 2,87 9,41 14,13
Phdn tram so vdi dien tich vting 6,08 1,14 0,17 7,29 2,38
• 0,51 0,97 78,39 1,99 1,07 100,00
80
Trang 3Bdng 2 Phan bo dat theo cac tmh Nam Trung Bo (ddn v j : ha)
Ten da't
Cdn cat va ddt cat ven biln
Dd't man
Dd't phen
Da't phil sa
Ddt Idy
Ddt den
Ddt nau vting ban khd han
Ddt xam
Ddt dd
Dd't xdi mdn tro sdi da
Cdng ddt
Sdng sudi
Niii da
Dao
Tdng dien tich tu nhien
Quiing Nam
-Da Ndng 43.119 15.417 2.155 75.428 14.993
984.424 3.652 5.436 1.144.624 21.391 2.024 30.498 1.198.537
Quang Ngai 14.389 6.947 41.967 8.463 1.903 398.735 20.606 2.021 495.031 10.650 12.024 517.705
Binh Dinh 18.250 11.581 77.318 18.430
125 427.771 16.545 4.300 574.320 15.658 17.617
607595
Phil Yen 12.984 3.701 3.930 29.355 24.705 , 19.919 376.914 34.228
55 505.791 5.640 17.090
528521
Khanh Hda 16.300 8.332 1.504 22.954 18.035
441.265
898 11.434 520.722 3.256 1.176
43 525.197
Ninh Thuan 13.148 2.294 13.611 5.184
32.930 249.560 3.990 16.952 337.669 1.929 3.062 342.660
Binh Thuan 146.985 1.288 57.356 14.133
294 9.400 539.113 6.713 6.430 781.712 5.376 12.112 799.200
Tdng dien tich 265.175 49.560 7.589 317.989 103.943 22.241 42.330 3.417.782 86.632 46.628 4.359.869 63.900 65.105 30.541 4.519.415
vting), hdu hit dugc hinh thdnh tren da magma acid
va da cat Do dd cdc loai ddt xam cd thanh phdn co
gidi nhe din trung binh (6]
b) Qua trinh thaai hda datva haang mac hda
Diiu kien phat sinh ddt ciia vung duyen hai Nam
Trung Bg da chira dung nguy co va tiim nang thoai
hda manh cua Idp phil thd nhuong Bdi vay qua trinh
thoai hda ddt hien tai diin ra nhanh vd sau sde Cudng
dd cila cac qua trinh thodi hda ciing diin ra theo nhjp
dieu miia Mtia mua la qua trinh xdi mdn nia trdi, sat
Id vtli la'p do nudc, cdn mtia khO la qua trinh cat bay,
cat nhdy, nhilm man Tinh ehdt khd dm theo chu ky
cung lam tang cudng qua trinh laterit hda thanh tao
da ong va kit von Cac qua trinh thodi hda ddt co
ban ddn din hoang mac hda trong vting bao gdm :
• Qua trinh xdi mdn rCfa trdi do nUdc ciia vimg
nghien ciru xd'y ra manh me vao mua mua hang nam,
manh nhdt d vting ddi thudc sudn Ddng Trudng Son
Tai day dg dd'c, chilu dai sudn va lugng mua diu
ldn Da't xdi mdn tro sdi da lau ngay tren 46.000 ha
thi hien td'c dO cua qud trinh nay Tdng ddy ddt ddi
niii cila vting phd biln dudi 50 cm chilm 15,5 % vd
nhilu noi dudi 30 cm chilm 48,5 % Dac biet cd thi
quan sat thdy nhirng dien tich ldn ddt cd da Ig, da lan
nhu Phan Rang - Thdp Cham (Ninh Thuta), Vinh
Hao - Ca Na (Binh Thuta), An Nhon (Binh Dinh),
Md Dire - Dire Phd (Quang Ngai) |4]
cat, noi ed lugng mua thdp vd himg chju gid biln, gid niii Cac cdn cat di chuyl'n sau vdo trong ddt liln, tde dd di chuyl'n cat cao 3-5 m/nam d Chi Cdng (Tuy Phong), MQi Ne (Phan Thilt) Nhilu bau nudc d vung cat bi can va bi viii ldp nhu : Bau Tan, Bau Can (Binh Thuta) Tinh khde nghiet cila mdi trudng gid'ng vdi sa mac Vai trd cila gid cdn tac dgng sau vao viing ddt xam bac mdu trudc nui Do riia trdi ddt bl mat bj "bac mdu", cdu triic ddt bj pha
vd toi bd rdi nen thudng bj gid cud'n tao thanh cac con ldc bui di chuyl'n Cac dam bui bj bdc mdn ttr noi nay, lai tich dgng d noi khac dudi dang bui tua
"hoang thd" la nguyen nhan chinh hinh thdnh nen hoang mac biii (hoang mac ddt can) [5 ]
• Qua trinh hinh thanh ke't van da ang (laterit
hda) phd biln d vung ddi tilp giap ddng bang vdi dien tich hang chuc ngan ha Su cd mat cila cac tdng
da ong ddy dac vira thi hien tinh ddi diin hinh nhiet ddi vira thi hien dilu kien phi dia ddi cua khu vuc
ed ehi dg khd dm chu ky Nhilu noi d cac huyen ven ddng bdng, da ong Id len mat ddt va dugc khai thae lam vat lieu xay dung Hdu hit cdc ddt xam bac mdu tren phti sa cd cd xudt hien kit von da ong Tdng
da ong da tao thanh mat chan dia hda, cdt dirt mdi quan he cila tdng ddt vdi mdu ehdt ben dudi Nhiing noi da ong Id tren mat, ddt trd thdnh "xuong xd'u" (da't xdi mdn tro sdi san) va ngheo dinh dudng Qua trinh hoang hda thi hien rd net vao mtia khd [5]
Trang 4tich luy mud'i tii nudc bil'n va tich liiy mud'i ttr phong
hda da me tao thanh dd't Hai don vj phat sinh nay
md rdng cung vdi qua trinh khd han Don vj nay dac
trung cho vung ban khd han Ninh Thuta - Binh Thuta
(Ninh Thuta cd tren 32.900 ha d huyen Ninh Son,
cdn Binh Thuta la 9.400 ha d huyen Tuy Phong)
Dua vdo dilu kien hinh thanh va tinh ehdt dac thu,
cac nha thd nhudng da xlp don vj ddt nay vao nhdm
ddt nau ban khd han Don vj ddt nay phdn Idn cdn
bd hoang vdi cd va cay bui xo xac Cac ddu tich
mud'i tren mat va trong tdng ddt thi hien qua trinh
man hda thir sinh
Su tuong tac giiia quy luat dja ddi, dia d va phi
dia ddi khac dii hinh thanh mgt birc kham thd nhudng
dac thu cila vimg Dai dien cho quy luat dia ddi la
nhdm ddt dd vang xam Quy luat dja d cd ddt cat,
da't man phen, ddt nau ban khd han Cdn quy luat
dai cao la ddt xam rntin tren niii Cung vdi dd la
qua trinh thoai hda ddt da hinh thanh ndn cac loai
"ddt cd vdn de" (soil problem) rdt dac thti va dien
tich kha ldn trong vting nghien ciru {bang 3) nhu
ddt xdi mdn tro sdi da, ddt xam bac mdu |6]
Dien tich "ddt c6 vdn dl" xudt hien trong vting
chie'm tdi 18,38 % tdng didn tich viing Tinh cd dien
tich "ddt cd vdn dl" ldn nhdt la Binh Thuta chiem
tdi 29,41 % dien tich tu nhien tinh Thdp nhdt la
Quang Nam - Da Nang (QN-DN) 9,55 % Cd ba tinh
"da't cd vdn dl" chilm tren 20 % dien tich la Binh
Djnh 26,21 %,PhuYen21,39 %, Ninh Thuta 20,76%
Cdn hai tinh cd dien tich "ddt cd vdn dl" trdn 10 %
la Khanh Hda 16.06 % va Quang Ngai 13,2 5% tdng dien tich ciia tinh "Ddt cd vdn dl" la san phdm cila qua trinh thoai hda da't tir nhien va nhta tac phan bd tren ta't ca cac dang dja hinh niii, ddi, ddng bang phti
sa sdng, ddng bang duydn hai Nam Trung Bd
2 Cac dang hoang mac hda a Nam Trung Bp
Thoai hda ddt lien tuc, md rdng se ddn din hoang mac hda Dd'i chie'u vdi cac tinh ehdt hoang mac tren the gidi cho thdy md'i quan he khang khit cua hai qua trinh nay O Nam Trung Bd ba dang
"da't cd vdn de" chie'm dien tich ldn nhdt la ddt cat, da't xam bac mdu va ddt xdi mdn tro sdi da (bang 3) Ddt cat bil'n phan bd chii yiu dgc theo bd bien
va chju anh hudng manh cua qua trinh phong thanh Hien tugng cat bay, cat nhdy dang diin ra rdt manh
d Bac Binh Thuta, Ninh Thuta va mdt sd duyen hai cua Quang Ngai, Binh Djnh Dd'i dien vdi ddt cat bil'n qua ddng bdng la dang dd't xam bac mdu va da't xdi mdn tra sdi da phan bd chii ye'u ven ddi nui tie'p giap ddng bdng Hai don vj "ddt cd vdn de" nay tham gia hinh thanh hai dai hoang mac ddt cin (btii) vd hoang mac cat ddng bdng nhd hep Dien
da cimg vdi dien tich nui da trgc khd ldn (chilm 1,44 %) da trd thanh cac hoang mac da thuc thu d Nam Trung Bd
Su xudt hien ddt nau vting ban khd han 42.330
ha tuong duong 0,97 % dien tich vimg va 202 ha ddt man kilm la nhirng chi thi cila qua trinh hoang
Bdng 3 Dien tich dat c6 van de cl cac tinh Nam Trung Bo (don vj : ha)
Ten da't
Da't cat
Ddt man
Da't phen
Ddt Idy
Ddt xam bac mdu
Da't xdi mdn tro
sdi da
Nui da
Tdng ddt (ddt +
niii da)
% so vdi DTTN
tinh
% so vdi DT ddt
cd vdn d l
Tdng dien tich tu
nhien viing
Quang Nam - Da Ndng 43.119 15.417 2.155 14.993 28.561 5.436 2.024 111.705 9,55 13,45
Quang Ngai 14.389 6.947 8.463 24.442 2.021 12.024 68.286 13,25 8,22
Binh 1 Dinh 18.250 11.581 18.430 88.140 4.300 17.617
Phu Yen
12.984 3.701 3.930 24.705 45.800
55 17.090 158.318 108.265 26,21
19,06
21,39 13,03
Khanh Hda 16.300 8.332 1.504 18.035 27.027 11.434 1.176 83.808 16,06 10,09
Ninh Thuta 13.148 2.294 5.184 54.536 16.952 3.062
^ " ^ " tich 146.985 265.175 1.288 49.560 7.589 9.124 98.934 29.190 297.696 6.430 46.628 12.112 65.105 69.830 230.475 830.687 20,76
8,41 4.519.415
29,41 27,75 100,00
% so vdi
DT dated vdndl 31,92 5,97 0,91 11,91 35,84 5,61 7,84 100,00
% so voi DTTN viing 5,87 1,10 0,17 2,19 6,59 1,03 1,44 18,38
• , • • - ' ? •
82
Trang 5mac hda Hai dan vi da't tren phan bd chil yiu d hai
tinh Ninh Thuta va Binh Thuta Vd cting d hai tinh
nay xudt hien mgt don vj "ddt hoang mac" dac biet
d Viet Nam, dd la cac cdn cat, bai cat dd vdi dien
tich 76.886 ha Khi nghien curu ngudn gd'c cila san
phdm cat dd cho thdy nd thi hien mgt dieu kien nhiet
ddi cd khd han Dd'i chilu vdi cdc dilu kien hoang
mac hda tren the gidi cd the khang djnh thoai hoa
dat vung duyen hai Nam Trung Bd ciing vdi su phan
hda mua mua - mtia khd sau sac la nguyen nhan co
ban dan din hoang mac hda da xdy ra ttr khd lau
cting vdi he thd'ng canh tac cila ngudi Cham
Ddt phd bie'n d cac vimg hoang mac tren thi gidi
bao gdm : ddt cat, ddt "xuong xdu", ddt man kilm va
da't mdi hinh thanh So sanh vdi ddt cila vung nghien
cuTj cung xudt hien cac da't tuong tu nhu ddt cat bien,
da't xdi mdn tro sdi da, ddt xam bac mdu, ddt man
Day la nhtrng "ddt cd vdn dl" dac thti cila khu vuc
mang nhiJng ddu hieu hoang mac hda [6]
Hoang mac hda tren the' gidi dugc phan loai theo
mirc dd (hoang mac - ban hoang mac) va theo tinh
chat, qua trinh thanh tao
So sanh vdi kit qua nghien ciru hoang mac hda
d viing Nam Trung Bd cd thi xdc djnh bd'n dang ban hoang mac hda xudt hien vdo mua khd hang nam
a) Ban hoang mac cat
Vdi dien tich tren 260.000 ha phan bd chii yiu dgc ven bil'n Bac Binh - Tuy Phong (Binh Thuta), Ninh Phudc - Ninh Hai (Ninh Thuta), Phii My - Phu Cat (Binh Dinh) Diin biln cat bay, cat chdy xdy ra manh vao mtia khd hang nam Hinh thai ban hoang mac cat gdm cac cdn cat djeh chuyl'n va cd djnh (cd nhiJng cdn cat cao tdi tren 100 ni), eac bai cat bang
vd nhiing ddng sdng cat Tren cac ban hoang mac eat tdn tai cac "bau nudc" nhu cac dc dao cila xir hoang mac Bau chira nude nhilu nai cung bj can ddn tao thanh cdc "bau can", "bau tan" Ddt cat cd mOi trudng trung tinh it chua Mun vd dam diu ngheo, eac ehdt khoang khac rdt it Dac trung cho loai ddt ban hoang mac cat la cd thdnh phdn co gidi edp hat 2-0,02 mm chiem tdi tren 95 % toan phdu dien va chil yiu la Si02 Thdnh phdn hda ly phdu dien NT3 (xa Nhan Hai, huyen Ninh Hai, tinh Ninh Thuta)
kha diin hinh eho ddt ban hoang mac cat {bang 4)
Bdng 4 Thanh phan hoa ly hoc phau dien NT3
Tong
dat
(cm)
0-20
20-40
pH
KCl
Mtin
%
Tdng sd (%) De tieu Cation trao doi
(mg/1 OOg da't) (meq/1 OOg dat) Phan tram Thanh phan co gidi (%)
N P2O5 K2O P2O5 K2O C a " M g " CEC Cl" SO/" 2-
0,02-0,02mm G,002mm 8,47 0,895 0,056 0,067 0,04 18,30 6,00 4,00 2,40 7,82 0,018 0,010 97,5 1,6
8,56 0,790 0,050 0,054 0,05 9,80 6,00 2,40 0,50 5,13 0,018 0,012 96,2 3,2
< 0,002mm
0,9 0,6
b) Ban haang mac da san soi
Dien tich tren 100.000 ha Id cdc nui da trgc va
ddi nui sdt xdi mdn tro sdi da dgc cac ddng bdng
ven bil'n ctia Ninh Thuta, Binh Thuta, Quang Ngai,
Binh Djnh, Khanh Hda Hinh thai cdu triic ddt xdi
mdn tro sdi da la ddt hd'c da hoac bl mat sdi san Ldp
phil thirc vat tren mat ddt thua thdt la cd cirng thdp,
cay gai, sdi da tro trdn mat ddt Tdng mim va tdng
tich til B hdu nhu bj cat cut, tdng ddt mdng dudi 30 cm
Thanh phdn edp hat chii yiu la sdi san, cat thd Thanh
phdn dinh dudng ngheo mtin, dam, lan, kali va cation
trao ddi Ddt chua din rdt chua Mdi trudng ddt ndng
ndng va gid bdo mdn vdo mua khd, cdn mtia mua bi
nudc xdi mdn va xdi Id Dd trtr dm ddt rdt thdp, nen
vao mtia khd trd thanh dang hoang mac ddt cdn
Ddt xdi mdn tro sdi da d Nam Trung Bd cd
46.628 ha, chilm 1,03 % tdng dien tich ddt tu nhien
vung ; phan bd d Ninh Thuta 16.952 ha, Khanh Hda
11.434 ha, Binh Thuta 6.430 ha, Quang Nam - Da Nang 5.436 ha, Binh Djnh 4.300 ha Dac biet niii da trgc trong khu vuc cd dien tich kha ldn (65.105 ha) phan bd d Binh Djnh vd Phii Yen diu tren 17.000 ha,
d Quang Ngai va Binh Thuta diu tren 12.000 ha, Ninh Thuta tren 3.000 ha, Quang Nam - Da Ndng tren 2.000 ha Da lan Id, nd nirt la nhirng ddu hieu thi hien tinh trang hoang mac da san sdi kha rd net
c) Ban hoang mac bui
Dien tich tren 290.000 ha, chilm 6,59% so vdi dien tich tu nhien ciia vung, la nhiing viing ddt xam bac mdu do bi rira trdi manh vung ban son dia giap ddng bang Tdng ddt mat bj pha vd cdu trite thanh dang bdt, biii vd tdng ben dudi thudng cd kit von
da ong Ddt chua din rdt chua, ngheo cac ehdt dinh dudng Dien phan bd tap trung ttr Quang Ngai din Binh Thuta Dac trung cho dang ban hoang mac biii cd phdu dien BTT1 thudc huydn Ham Tan tinh
Trang 6Binh Thuta Hien trang sir dung dd't: cay bui, sim,
mua thanh phdn co gidi cua ddt nhe do cac edp
hat set da bj rura trdi {bdng 5)
d) Ban hoang mac mud'i
Dien tich tren 49.000 ha phan bd chu yiu d Ninh
Son, Ninh Hat (Ninh Thuta), Tuy Phong - Bdc Binh
(Binh Thuta), Sa Huynh, Son Tjnh (Quang Ngai) ;
ven ddm Nha Phu d Ninh Hda (Khanh Hda), ven
ddm O Loan d Tuy An (Phii Yen) Ddt cd ham lugng
dinh dudng tu nhien trung binh din kha, ham lugng
chat hihi CO da't trung binh, cd thanh phdn co gidi
ttr thit trung binh d ldp dudi va thit nang d Idp mat
Song ham lugng mud'i Cl va SO4 cao Phdu dien
NT4 thudc xa Nhan Hai, Ninh Hai, Ninh Thuta dac
trung cho dang hoang mang mudi nay {bdng 6)
Hien trang ban hoang mac trong viing cd quy
md khOng ldn dang da bao Song nguy co trd thanh
ban hoang mac thirc thu Id rdt ldn Bdi vi hien tugng
va qua trinh thodi hda ddt ngay cang tang cudng do
nhu cdu khai thac da't dai ngay cang tang va cac hoat
ddng thien tai xudt hien ngdy cang nhilu nhu khd
ndng, nudc bien dang do bien ddi khi hta
Quy luat phan bd cac dang hoang mac hda trong
vting dan xen md rgng ttr bdc vdo nam va t h i hien
rd nhdt d khu vuc Ninh Son - Ninh Hai (Ninh Thuta)
de'n Ham Thuan (Binh Thuta) Ttr dgng sang tay
viing phan bd hoang mac hda chil ye'u d hai dai
hoang mac hda cat va man duyen hai va hoang mac
hda da, ddt cdn ddi thim chan Trudng Son
Qua phan tich cac dac trung phat sinh vd thoai hda da't cho tha'y thoai hda ddt thuc sir la mdt trong nhiing nguyen nhan ca ban ddn din hoang mac hda
d Nam Trung Bd Trong dd thodi hda ddt tiim nang (thoai hda tu nhidn do cac qua trinh dja cha't, dja hinh, da me, khi hau ) vd thoai hda hien tai (thoai hda nhdn tac) diu t h i hien cudng dd manh me Hoang mac hda hinh thanh trong dilu kiln khi hau nhiet ddi gid mtia, vdi sir phdn hda mtia mua va khd sau sde cdng vdi ydu td kiln tao dja mao dac biet vd sir tuong tac cUa qua trinh sdng - bien - liic dia Nguy co thoai hda ddt cua vting ldn nen nhilu qua trinh thoai hda ddt da diin ra manh vd sau sde Trong dd cac qua trinh uu the' la qua trinh xdi mdn
do nudc, do gid, qua trinh laterit hda, qua trinh man hda Thoai hda ddt hien tai do khai thac khdng hgp
ly cua con ngudi t h i hien trong hien trang sii dung ddt vdi dien tich rtrng ngay cang bj thu hep va ddt trd'ng ddi niii trgc ngay cdng tang Dien tich nui da trgc tren 65.000 ha va hon 44.(X)0 ha ddt hoang trdng Ban hoang mac cat phd bie'n d Ninh TTiuta, Binh Thuta Ban hoang mac da va ban hoang mac ddt cdn phd biln d Quang Ngai, Binh Djnh, Phu Yen Qua trinh thoai hda da't lan rdng lam giam kha nang du trtr nudc, tang cudng bd'c hoi va lam tang them tinh khde nghiet cila mtia khd Dd la mdt trong nhirng nguyen nhan xudt hien cdc dang ban hoang mac hda nhu : ban hoang mac cat, ban hoang mac da sdi, ban hoang mac biii Nhu vay dilu kiln dja Iy phat sinh
- thoai hda va hoang mac hda trong vimg phan anh quan he chat che Thoai hda ddt va hoang mac hoa
Bdng 5 Thanh p h i n ly hoa hoc da't p h l u dien BT11
Tdng ddt
(cm)
0-13
13-30
>30
pH
KCl
4,45
4,27
4,33
Mun
%
1,018 0,175 0,299
Tdng sd (%)
N P2O5 K2O 0,061 0,030 0,04 0,11 0,007 0,012 0,011 0,020 0,04
Cation trao ddi (meq/1 OOgddt) Ca^" Mg** CEC 2,00 0,40 4,62 0,40 0,30 3,22 0,40 0,20 2,17
Thanh phdn ca gidi 2-0,02mm J ^ 2 m m < 0 ' 0 0 2 m m 85,50 10,40 4,10 82,10 14,30 3,60 79,60 15,60 4,80
Tdng
ddt
(cm)
Bdng 6 Tinh chat ly hoa hoc dat p h i u dien NT4
KCl %
0,02-0-20 7,10 1,79 0,117 0,094 0,23
20-40 8,01 1,10 0,07 0,078 0,18
40-60 7,85 0,89 0,06 0,041 0,12
60-100 7,55 0,89 0,05 0,034 0,16
9,90 16,9 4,50 3,5
57,0 13,60 7,40 45,0 12,4 7,60 48,0 7,40 5,60 30,0 5,60 4,40
r ^ 0.02mm 0.002mm 25,49 0,745 0,20 34,5 28,4 21,39 0,335 0,06 60,76 13,22 14,53 0,417 0,07 67,44 8,60 12,44 0,417 0,056 70,08 7,10
< 0,002mm 37,2 26,02 23,96 22,82
84
Trang 7la hai budc suy thoai mdi trudng nghiem trgng cdn
dugc khac phuc dua tren cac hilu bilt vl phdt sinh
dd't trong vung
III VAN DE Sir DUNG DAT TRONG VtfNG
HOANG MAC HOA
Tren CO sd phan loai, ddnh gia cu thi cac dang
hoang mac hda khu vuc nghien ciru cting vdi cac
muc tieu khai hoang phdt tril'n kinh te' xa hdi dl dua
ra cac giai phdp khai thac sii diing hgp ly d mdi dja
phuang Quan dilm chuyl'n ddi co cdu cay trdng
thich irng vdi viing hoang mac hda va tilp din la cac
giai phap cdng trinh vd phi cdng trinh ngan ngira,
phuc hdi cai tao viing hoang mac hda Cu the :
Dd'i vdi ddt man vting ven bil'n (nguyen nhan
chinh gay hoang mac man) chi sir dung han chi vao
trong ndng nghiep trdng trgt vdi viec ddu tu thily lgi
hoac lam liia mgt vu vao miia mua Phdn cdn lai gay
rtrng ngctp man chdn sdng ben ngodi, ben trong la
ddm nudi trdng thily san
Ddi vdi ddt cat (nguyen nhan gay hoang mac
cat) Ddt cat biln bdng cd thi khai thac trdng cac
cay rau qua ngdn ngdy d nhiing nai thuta nudc tudi
va cdn ddu tu phan hu'u co Phdn cdn cat, ddt cat
bil'n gd ghi trdng cay cdng nghiep dai ngay nhu
dieu, cay an qua va riing chju han
Ddi vdi da't xdi mdn tro sdi da (nguyen nhan gay
hoang mac ddt can va hoang mac da san sdi) khoanh
nudi, phuc hdi rimg la chil yiu Ben canh don vi ddt
nay thudng la ddt xam bac mdu tap trung trdng cay
cdng nghiep dai ngay, cay an qua Cac md hinh
ndng lam kit hgp va RVAC cdn dugc nhan rdng
trong todn khu vuc
Ben canh cdc hudng sii diing tren cdn dp dung
ddng thdi cac giai phap cdng trinh chdng xdi mdn,
sat Id va xay dung cac hd dap trtr nudc Ngodi ra cdn
sii dung cac san phdm cdng nghe phan bdn hiru co
sinh hgc, ehdt giii dm cho ddt trong khu vuc
Cac chinh sach ddu tu cai tao ddt, giao ddt, thue
ddt cdn dugc chinh phii uu tien
KET LUAN
Qua cac kit qua nghien ciru eho thdy vting Nam
Trung Bg xudt hien bd'n dang hoang mac hda diin
hinh sau : bdn hoang mac cdt : vdi didn tich tren
260.000 ha phan bd chii yiu dgc ven bil'n Bac Binh
- Tuy Phong (Binh Thuta), Ninh Phudc - Ninh Hai
(Ninh Thuta), Phu My - Phu Cat (Binh Djnh) Bdn hoang mac dd san soi: dien tich tren 100.000 ha la
cac nui da trgc va ddi niii sdt xdi mdn tro sdi da dgc cac ddng bang ven biln cua Ninh Thuta, Bin i Thuta,
Quang Ngai, Binh Djnh, Khanh Hda Bdn hoang mgc mud'i : dien tich tren 49.000 ha phan bd chu yiu d
Ninh Son, Ninh Hai (Ninh Thuta), Tuy Phong - Bac Binh (Binh Thuta), Sa Huynh, Son Tjnh (Quang Ngai), ddm Nha Phu d Ninh Hda (Khanh Hda), ddm
O Loan d Tuy An (Phii Yen) Bdn hoang mgc bui :
dien tich tren 290.000 ha, chilm 6,59 % so vdi dien tich tu nhien cila vting phan bd tap trung tir Quang Ngai de'n Binh Thuta
Dien hoang mac hda hien tai xdy ra cue bd d cac dia phuang, song td'c dd ngay cang tang vd cd nguy
CO gdn kit vdi nhau tao thanh khu vuc ldn, rdt khd khde phiic
Thoai hda ddt thuc sir la mdt trong nhtrng nguyen nhan eo ban ddn din hoang mac hda Trong dd thoai hda tiim nang thi hien trong cdu trite dia hinh khu vuc mdt vting khd (it mua) cue bg va thdnh phdn mdu chat hinh thdnh ddt da phdn la ngheo va tao ra da't cd thanh phdn co gidi nhe, du trtr dm kem Quy luat tuong tac song bien vd phong hda rira trOi lau ddi lam cho ddt ngay cang ngheo Hien tugng
IQ quet va bil'n ldn dang diin ra vdi cudng dd Idn
la tiin dl hoang mac hda manh [5 ]
Sir gia tang dta sd va khai thac lau dai vdi phuang thirc canh tac lac hau nhu ddt nuong lam rdy, chan tha gia siic qua tai va hta qua ciia chiln tranh da ddn de'n hien trang thoai hda ddt va hoang mac hda hien nay
TAI LIEU DAN
]1] NGUYIN VAN CU, NGUYIN DINH KY, NGUYIN LAP DAN, 1998 : Hoang mac hda - vdn
de mdi trudng edp bach vting Nam Trung Bg Viet Nam Bao cao hgi nghi mOi trudng toan qud'e
Ha Ndi
[2] NGUYIN VAN CU, NGUYIN DINH KY, NGUvtN LAP DAN, 1998 : Quan dilm tdng hgp trong nghien cim hoang mac hda vd lu lut Nam Trung Bd Viet Nam Bao cao hgi nghj KHCN vd
MT viing Nam Trung Bg vd Tay Nguyen, Pleicu [3] NGUYfiN DINH KYva nnk, 1997 : Nghien ciiu tai nguyen mdi trudng ddt vting hoang mac hda Ninh Thuta - Binh Thuta Bao cao luu trir Vien Dja ly
Trang 8]41 NGUYEN DINH KY va nnk, 1997 : Nghien
ciru tai nguyen mdi trudng dd't vting hoang mac
hda Quang Ngai - Binh Djnh Bao cao luu trtr Vien
Dja ly
15] NGUYEN DINH KY, 1998 : Quan he dja Iy
phat sinh va thodi hda ddt Tuyl'n tap cdng trinh
nghien cim dja ly Nxb Khoa hgc va ky thuat Ha Ndi
|6] NGUYEN DINH KY va nnk, 2002 : Nghien
ciru dd't cd vdn dl vting duyen hai Nam Trung Bd
Viet Nam Bdo cdo luu trii Vien Dia ly
]7 ] Chuang trinh htah ddng qud'e gia phdng chd'ng
sa mac hda va Cdng udc chd'ng sa mac hda ciia Lien
Hgp Qudc
S U M M A R Y
The soil degaradation and desertification in South
Central Vietnam The soil degaradation and desertification are
affects resulting from the loss of the ecological balance
by the natural processes and socio-economical
activities in the arid, semi-arid and dry sub-humid
areas According the geo-synthetization, the soil
degradation is a main cause leading to the
deserti-fication
In Central Southern of Vietnam, the condition of
the soil originating (from Da Nang to Binh Thuan
area) is belonged to the monsoon of the tropical
climate with 6-9 dry months Particularly, the Ninh
Thuan - Binh Thuan area has 8-9 dry months that
is identical to a semi-arid area, occupying -45,000
km^ The structure of the soil layer is complicated
with 10 groups, 20 types of the soil layer, more
than 65,000 ha of the mountain land, and
265,000 ha of the sand-dune and sand beach
The area has high potential of soil degradation
and it is happening strongly after seasons One of
the main reason of the soil erosion is water current
in the steep area, by winds in the coastgl sandy
area, laterization in the hill area, and salinization in the coastal area, etc In this area, the average soil loss by the water current is ranging from 400-800 ton/ha per year, in the places this number is up to 1,000 ton/ha per year Consequently, 48 % of the area in the upper4and has thin soil layer below
30 cm and over 30 % of the area in the lowland has light mechanical components Furthermore, it is leading to the low water- bearing capacity of the soil, as well as increasing of the evaporation rate, promoting desertification processes in these areas According to the world's classification, 4 types
of desertification are presented in the Central Southern of Vietnam as followed :
- Sandy desert : this type is occupy about of 260,000 ha, mainly locating in Binh Thuan, Ninh Thuan and Binh Dinh provinces ;
- Rocky-stone desert : this type of desert has about of 100,000 ha, distributing in Quang Ngai, Binh Dinh, Khanh Hoa, Ninh Thuan and Binh Thuan provinces ;
- Dust desert: the total area of this type of desert has about 290,000 ha, comprising infertile gray soil and erode soil with grave and stone They are distribu-ted along the foot of the Truong Son Mountain to the plain land near the coastal line, from Quang Ngai
to Binh Thuan provinces;
- Salt desert: It has about of 49,000 ha and concentrated in Ninh Thuan and Binh Thuan pro-vinces
The rule of the distribution of the desertification is increase from the North to the South and from the East
to the West in the South Central Vietnam, so that, creating the two desert bands, one is near the coast and other is at the foot of the Truong Son mountain The trend of the soil degradation and desertification
is increasing and spreading out, requiring more atten-tion in controlling, managing, as well as recovering
Ngdy nhdn bdi : 27-11-2009
Vien Dia Iv
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