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[.]
32(1), 79-86 Tap chi CAC KHOA HOC v g TRAI BAT 3-2010 THOAI HOA DAT VA QUA TRINH HOANG MAC HOA 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 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 cdc yiu td khac bao gdm sir biln ddi hau va cac hoat ddng cila ngudi Suy thoai ddt la su suy giam hoac mdt nang sudt sinh hgc vd kinh tl 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 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 - 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 niii da, tren 265.000 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 Su thiet hai thoai hda ddt va hoang mac hda phat tril'n kinh tl - 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 Dieu kien hinh va cic qua trinh thoai hda d&'t vung Nam Trung Bp a) Dieu kien hinh 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 kit qua tuong tac lau dai va phirc tap dd Dilu kien sinh hau thd nhudng cila viing nam trgn 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 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 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 xud'ng dudi 500 mm) Quy luat 79 phdn 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 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 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 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 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 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 vimg phan hda ro ret theo dilu kien 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 vung cd tren 65.000 niii da trgc vdi cay bui gai, hd'c da va han 44.000 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 manh nhdt Ngoai cac cudc chie'n tranh keo dai ttr xa xua din nam 1975 cung la mdt nhirng nguydn nhan ctia tinh trang thoai hda da't va hoang mac hda 12] Tir cac dilu kidn phat sinh ddt da hinh 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 vting {bdng 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, vting nghien cim cd bd biln keo ddi tren 700 km Nhdm da't cat va cdn cat vting chie'm gdn 50 % dien tich loai ddt ca nudc Nhdm ddt nau vung ban khd han 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 Dien tich cac nhom da't vung duyen hai Nam Trung Bo Duyen hai Nam Trung Bd Dien tich ca Dien tich Phdn tram so vdi Phdn tram so vdi Nhdm ddt nudc (ha) loai ddt ca nudc (ha) dien tich vting Cdn cat vd ddt cat ven biln Da't man Ddt phen Ddt phti sa Ddt Idy 4- ddt giay chua 533.434 971.356 1.863.128 3.400.059 452.418 265.175 49.560 7.589 317.989 103.943 49,71 5,10 0,41 9,35 22,97 Ddt den Dd't nau vting ban khd han Ddt xam Dd't dd Ddt xdi mdn tro sdi da Tdng cdng 112.939 42.330 19.970.642 3.014.594 495.727 30.856.627 22.241 42.330 3.417.782 86.632 46.628 4.359.869 19,69 100,00 17,11 2,87 9,41 14,13 80 6,08 1,14 0,17 7,29 2,38 • 0,51 0,97 78,39 1,99 1,07 100,00 Bdng Phan bo dat theo cac tmh Nam Trung Bo (ddn vj: ha) Ten da't Cdn cat va ddt cat ven biln Dd't man Dd't phen Da't phil sa Ddt Idy Quiing Nam - Quang Da Ndng Ngai 43.119 15.417 2.155 75.428 14.993 Binh Dinh Phil Yen 14.389 6.947 18.250 11.581 41.967 8.463 77.318 18.430 12.984 3.701 3.930 29.355 24.705 Khanh Hda 16.300 8.332 1.504 22.954 18.035 Ninh Thuan Binh Thuan 13.148 146.985 2.294 1.288 13.611 5.184 57.356 14.133 Tdng dien tich 265.175 49.560 7.589 317.989 103.943 Ddt den Ddt nau vting ban khd han Ddt xam Ddt dd Dd't xdi mdn tro sdi da 984.424 3.652 5.436 294 22.241 9.400 32.930 42.330 398.735 427.771 376.914 441.265 249.560 539.113 3.417.782 20.606 898 16.545 34.228 3.990 6.713 86.632 2.021 55 4.300 11.434 16.952 6.430 46.628 Cdng ddt Sdng sudi Niii da Dao Tdng dien tich tu nhien 1.144.624 21.391 2.024 30.498 1.198.537 495.031 574.320 505.791 520.722 337.669 781.712 4.359.869 10.650 15.658 1.929 5.640 3.256 5.376 63.900 12.024 17.617 17.090 1.176 3.062 12.112 65.105 43 30.541 517.705 607595 528521 525.197 342.660 799.200 4.519.415 1.903 vting), hdu hit dugc hinh thdnh tren da magma acid va da cat Do dd cdc loai ddt xam cd 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 nhanh vd sau sde Cudng dd cila cac qua trinh thodi hda ciing diin theo nhjp dieu miia Mtia mua la qua trinh xdi mdn nia trdi, sat Id vtli la'p 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 tao da ong va kit von Cac qua trinh thodi hda ddt co ban ddn din hoang mac hda vting bao gdm : 125 , 19.919 cat, noi ed lugng mua thdp vd himg chju gid biln, gid niii Cac cdn cat di chuyl'n sau vdo 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 cac 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 ke't van da ang (laterit hda) phd biln d vung ddi tilp giap ddng bang vdi • Qua trinh xdi mdn rCfa trdi nUdc ciia vimg dien tich hang chuc ngan Su cd mat cila cac tdng nghien ciru xd'y manh me vao mua mua hang nam, da ong ddy dac vira thi hien tinh ddi diin hinh nhiet manh nhdt d vting ddi thudc sudn Ddng Trudng Son ddi vira thi hien dilu kien phi dia ddi cua khu vuc Tai day dg dd'c, chilu dai sudn va lugng mua diu ed ehi dg khd dm chu ky Nhilu noi d cac huyen ldn Da't xdi mdn tro sdi da lau tren 46.000 ven ddng bdng, da ong Id len mat ddt va dugc khai thi hien td'c dO cua qud trinh Tdng ddy ddt ddi thae lam vat lieu xay dung Hdu hit cdc ddt xam bac niii cila vting phd biln dudi 50 cm chilm 15,5 % vd mdu tren phti sa cd cd xudt hien kit von da ong Tdng nhilu noi dudi 30 cm chilm 48,5 % Dac biet cd thi da ong da tao mat chan dia hda, cdt dirt mdi quan sat thdy nhirng dien tich ldn ddt cd da Ig, da lan quan he cila tdng ddt vdi mdu ehdt ben dudi Nhiing nhu Phan Rang - Thdp Cham (Ninh Thuta), Vinh noi da ong Id tren mat, ddt trd thdnh "xuong xd'u" Hao - Ca Na (Binh Thuta), An Nhon (Binh Dinh), (da't xdi mdn tro sdi san) va ngheo dinh dudng Qua trinh hoang hda thi hien rd net vao mtia khd [5] Md Dire - Dire Phd (Quang Ngai) |4] • Qua trinh thai mdn va di chuyen cat da gid : • Qua trinh man hda phen hda (man Cl' va phd biln d vimg duyen hai Dac biet tren cac vung man SO/'): vung cd hai ngudn gd'c chinh la tich luy mud'i tii nudc bil'n va tich liiy mud'i ttr phong hda da me tao dd't Hai don vj phat sinh md rdng cung vdi qua trinh khd han Don vj dac trung cho vung ban khd han Ninh Thuta - Binh Thuta (Ninh Thuta cd tren 32.900 d huyen Ninh Son, cdn Binh Thuta la 9.400 d huyen Tuy Phong) Dua vdo dilu kien hinh va tinh ehdt dac thu, cac nha thd nhudng da xlp don vj ddt vao nhdm ddt nau ban khd han Don vj ddt phdn Idn cdn bd hoang vdi cd va cay bui xo xac Cac ddu tich mud'i tren mat va 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 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 ndn cac loai "ddt cd vdn de" (soil problem) rdt dac thti va dien tich kha ldn 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 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 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 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 Hien tugng cat bay, cat nhdy dang diin 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" tham gia hinh 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 cac hoang mac da thuc thu d Nam Trung Bd Su xudt hien ddt nau vting ban khd han 42.330 tuong duong 0,97 % dien tich vimg va 202 ddt man kilm la nhirng chi thi cila qua trinh hoang Bdng 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 82 Quang Quang Nam - Da Ngai Ndng Binh 1Phu Yen Khanh Dinh Hda 43.119 15.417 2.155 14.993 28.561 8.463 24.442 5.436 2.021 4.300 2.024 12.024 17.617 111.705 14.389 6.947 Ninh Thuta ^"^" tich 18.250 12.984 16.300 13.148 146.985 265.175 11.581 3.701 8.332 2.294 1.288 49.560 3.930 1.504 7.589 18.430 24.705 18.035 5.184 9.124 98.934 88.140 45.800 27.027 54.536 29.190 297.696 % so vdi % so voi DT dated DTTN vdndl viing 31,92 5,97 0,91 11,91 35,84 5,87 1,10 0,17 2,19 6,59 46.628 5,61 1,03 12.112 65.105 7,84 1,44 68.286 158.318 108.265 83.808 69.830 230.475 830.687 100,00 18,38 55 11.434 17.090 1.176 16.952 3.062 9,55 13,25 26,21 21,39 16,06 20,76 13,45 8,22 19,06 13,03 10,09 8,41 4.519.415 6.430 29,41 27,75 100,00 •.,••-' ?• mac hda Hai dan vi da't tren phan bd chil yiu d hai tinh Ninh Thuta va Binh Thuta Vd cting d hai tinh 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 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 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 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 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 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 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 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 Thanh phan hoa ly hoc phau dien NT3 Tdng sd (%) De tieu Cation trao doi Phan tram (mg/1 OOg da't) (meq/1 OOg dat) Tong dat (cm) pH KCl 0-20 20-40 8,47 0,895 0,056 0,067 0,04 18,30 6,00 4,00 2,40 8,56 0,790 0,050 0,054 0,05 9,80 6,00 2,40 0,50 Mtin % N P2O5 K2O P2O5 K2O C a " M g " CEC b) Ban haang mac da san soi Dien tich tren 100.000 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 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 Cl" SO/" 7,82 0,018 0,010 5,13 0,018 0,012 Thanh phan co gidi (%) 0,02- < 0,002mm 20,02mm G,002mm 97,5 96,2 1,6 3,2 0,9 0,6 11.434 ha, Binh Thuta 6.430 ha, Quang Nam - Da Nang 5.436 ha, Binh Djnh 4.300 Dac biet niii da trgc 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 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 bi rira trdi manh vung ban son dia giap ddng bang Tdng ddt mat bj pha vd cdu trite 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 83 Qua phan tich cac dac trung phat sinh vd thoai hda da't cho tha'y thoai hda ddt thuc sir la mdt 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 cac qua trinh dja cha't, dja hinh, da me, hau ) vd thoai hda hien tai (thoai hda nhdn tac) diu t h i hien cudng dd manh me Binh Thuta Hien trang sir dung dd't: cay bui, sim, mua phdn co gidi cua ddt nhe cac edp hat set da bj rura trdi {bdng 5) d) Ban hoang mac mud'i Dien tich tren 49.000 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 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 {bdng 6) Hoang mac hda hinh dilu kiln 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 manh vd sau sde Trong dd cac qua trinh uu the' la qua trinh xdi mdn nudc, gid, qua trinh laterit hda, qua trinh man hda Thoai hda ddt hien tai khai thac khdng hgp ly cua ngudi t h i hien hien trang sii dung ddt vdi dien tich rtrng cang bj thu hep va ddt trd'ng ddi niii trgc cdng tang Dien tich nui da trgc tren 65.000 va hon 44.(X)0 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 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 vimg phan anh quan he chat che Thoai hda ddt va hoang mac hoa Hien trang ban hoang mac viing cd quy md khOng ldn dang da bao Song nguy co trd ban hoang mac thirc thu Id rdt ldn Bdi vi hien tugng va qua trinh thodi hda ddt cang tang cudng nhu cdu khai thac da't dai cang tang va cac hoat ddng thien tai xudt hien ngdy cang nhilu nhu khd ndng, nudc bien dang bien ddi hta Quy luat phan bd cac dang hoang mac hda vting dan xen md rgng ttr bdc vdo nam va thi 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 Bdng Thanh phin ly hoa hoc da't phlu dien BT11 Tdng ddt pH KCl (cm) 0-13 13-30 >30 Mun % Tdng sd (%) N P2O5 K2O Cation trao ddi (meq/1 OOgddt) Thanh phdn ca gidi Ca^" Mg** CEC 2-0,02mm J ^ m m < ' 0 m m 4,45 1,018 0,061 0,030 0,04 2,00 4,27 0,175 0,11 0,007 0,012 0,40 4,33 0,299 0,011 0,020 0,04 0,40 0,40 0,30 0,20 4,62 3,22 2,17 85,50 82,10 79,60 10,40 14,30 15,60 4,10 3,60 4,80 Bdng Tinh chat ly hoa hoc dat p h i u dien NT4 Tdng pH Miin ddt (cm) KCl % 0-20 20-40 40-60 60-100 84 7,10 8,01 7,85 7,55 1,79 1,10 0,89 0,89 'TdngsdW N Cation trao ddi De tieu (mg/lOOgdat) (meq/1 OOg da't) P2O5 K2O P2O5 K2O Ca** Mg** CEC 0,117 0,094 0,07 0,078 0,06 0,041 0,05 0,034 0,23 9,90 57,0 13,60 7,40 0,18 16,9 45,0 12,4 7,60 0,12 4,50 48,0 7,40 5,60 0,16 3,5 30,0 5,60 4,40 25,49 21,39 14,53 12,44 Phdn tram Thanh phta ca gidi (%) Cl' SO, r ^ 0.02mm 0.002mm < 0,002mm 0,745 0,335 0,417 0,417 0,20 34,5 0,06 60,76 0,07 67,44 0,056 70,08 0,02- 28,4 13,22 8,60 7,10 37,2 26,02 23,96 22,82 la hai budc suy thoai mdi trudng nghiem trgng cdn dugc khac phuc dua tren cac hilu bilt vl phdt sinh dd't 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 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 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 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 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 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 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 cdn sii dung cac san phdm cdng nghe phan bdn hiru co sinh hgc, ehdt giii dm cho ddt 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 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 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 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 cue bd d cac dia phuang, song td'c dd cang tang vd cd nguy CO gdn kit vdi tao khu vuc ldn, rdt khd khde phiic Thoai hda ddt thuc sir la mdt nhtrng nguyen nhan eo ban ddn din hoang mac hda Trong dd thoai hda tiim nang thi hien 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 da't cd phdn co gidi nhe, du trtr dm kem Quy luat tuong tac song bien vd phong hda rira trOi lau ddi lam cho ddt cang ngheo Hien tugng IQ quet va bil'n ldn dang diin 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 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 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 85 ]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 SUMMARY 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 desertification 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 of the mountain land, and 265,000 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 86 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, 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 distributed 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 and concentrated in Ninh Thuan and Binh Thuan provinces 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 attention in controlling, managing, as well as recovering Ngdy nhdn bdi : 27-11-2009 Vien Dia Iv ... sdng, ddng bang duydn hai Nam Trung Bd 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... 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 tao So sanh vdi kit qua nghien ciru hoang mac hda d viing Nam. .. NGUvtN LAP DAN, 1998 : Quan dilm tdng hgp 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,