35(4), 364-373

Tap chi CAC KHOA HQC V£ TRAI S A T

©ANH GIA ANH HU'ONG CUA DIEU KIEN KHI HAU
^ NONG NGHIEP DEN CAY TRONG N G A N N G A Y
d KHU VUC NINH THUAN VA BINH THUAN
PHAM QUANG VINH', NGUYEN THANH BINH', BUI TH| THANH HU'ONG^
E-mail: [email protected]
' Viin Dia Ly. Vien Hdn ldm Khoa hgc vd Cong nghe Viet Nam
Tru&ng Cao ddng Suphgm Hd Ngi
Ngay nhan bii: 10 - 9 - 2013
1. Mddau

Ninh Thuin va Binh Thuan la hai tinh nam d
cue Nara Trung bfl Vift Nam, cd tdng dien lich
khoang I1.165km^, vdi 350km dudng bd bifln
{hinh 1). Khu vgc nay dugc dac trung bdi khi hau
am va bin khd ban, cd khoang gin ragt nua difn

tich li khd ban vi ban khd han, do do diy Ii khu
vuc hing nam da va dang pbii ddi difln vdi linh
Irgng thieu nudc keo dii, cd khoing 6 din 9 thing
khd moi nim (lugng mua dudi 100mm). Noi day
ciing chju inh budng eua diflu kien nhift dfl cao vi
gid manh, li nhdng yeu td gdp phin thiic day qua
trinh ban ban, hoang mgc bda.

Ch6 giii
Khu VV6 nglMfl cthi
Ranh gidi Huy^

thu^t toan, trong dd rad hinh Budget la md hinh
dugc ling dgng rgng rai trong tinh toan ein bing
nudc v i ude tinh raiic suy giira nang suat ciy
udng Iheo phin tram. Do dd vifle sii dung mo hinh
Budget xii ly cic dii liflu khi tugng ngiy dfl linh
toin can bing nudc phgc vg dinh gia tinh Irang
khd hgn doi vdi mflt sd ciy trdng ngin ngiy d tinh
Ninh Thuin v i Binh Thuin, nhira dua ra kit qua
vl miic dg suy giim ning suit ciy trdng (theo ty lfl
%) li ling dgng bit siic cin thilt. Kflt qui nghien
cuu niy li ca sd khoa hgc eho cie nha quin ly bfl
Iri diay dfli co ciu miia vg, thiet kfl c i y trong Ihieh
img vdi hgn ban, hoang mgc hda va bifln ddi
khi h^u.
2. Phuvng p h i p va dii' li^u nghien eiru

thoii nang suit trong giai doan cay trdng cin thiflt
nudc nhit [3].
MLFC dg suy giam ning suit cua cdy bdng
ndng nghiflp
Dinh g i i miic suy giim ning suit cay trdng
thuc tfl so vdi diflu kifln tfli uu dya tren phuong
phap ciia Jenssen (1968) [2], Iheo cdng thuc (I):

=n(:

CTnrtj

i«





Bdo LOc
Nha Trang
Pttan Rang
Phan Thidt
VOng tiu
Xuan L9c

LAn
nhdt
28
30
32
31
31
32

Db im khOng khi%)

Nhd nhdt Trung binh
IB
24
24
18
29
22

56
76
71

2552
1332
1768
1970
2597

Kilu khi h|lu
quan b ^ )

Am

30
28
28
26
26
18

Ban kho
Kho - ban am
Banlm
Banim
Am

ChO thich: (-) Id Ihi^u dO li$u

Sau trgm khi tugng phin bd deu xung quanh nghiflp. 0 nghien cuu niy chiing tdi tap trung phin
hai tinh Ninh Thuan vi Binh Thuin (hinh 3), Irong lich dQ lieu khi lugng dugc tdng hgp theo hang
dd ed tram Phan Thiflt va Phan Rang nam trung nam {bdng 2).
khu vgc nghien citu va nd phan inh khi diy dii


30

803

1266

2552

1590

28

449

638

1332

1868

1.

784

1142

1768

1758

dii\ la khu vgc phii hgp vdi nhiflu loai ciy ndng
nghiep khac nhau, Ngugc lgi, vdi lugng raua trung
3. Ket qui nghien curu
binh bang nim khi thip, chi khoing 800mm, Phan
3,L Bgc diim khi hgu ndng nghidp khu vifc NinhRang vi Phan Thiflt li hai trgm cd kieu khi hiu bin
kbd. Cd nhung n3m, lugng mua dudi 500mm/nam
Thugn vd Binh Thugn
di gay ra nhiing thiflt hgi ldn ve miia mang. Ngoii
Nhiflt dd, lu^ng mu'a v i boc thoat ho-i nudc:
viflc phal trifln hfl thdng thiiy lgi, d nhiing khu vgc
Ddi vdi nin ndng nghiflp chua phil tnen nhu d cd lugng mua thap nhu Phan Rang vi Phan Thiflt
Viflt Nam (hfl thfing thiiy lgi cdn yflu kem), thi miia cin chgn Iga nhung logi ciy chiu hgn tflt, thich urng
vg phy thugc cbii ylu vio lugng mua. Vi vgy, die vdi die diflm khi hgu nai day.
dilm diu tifln quan trgng cua khi h§u ndn§ nghiflp
Trgm Xuan Lgc vi Vung Tau cd lugng mua
cin xem xet dd li lugng mua. Cd thfl ndi ring mua
li dilu ki?n thiiy Igi tit nhat cho sin xuit ndng cao vi khi deu qua cic nkm, lugng mua nam khfl


vi nam am khdng chflnh nhau nhiflu, do dd ddi vdi
nen ndng nghiep Iua nude nhu nudc ta dac diflm
niy cd y nghia rat quan trgng. Nha Trang cung la
khu vuc cd Iugng mua Idn, nhung Iugng mua bing
nam d day khdng dflu, miic dd chflnh Iflch giua
nam khd vi nam am li rat cao, ngoai vin dfl thiflu
nudc do khd hgn, khi hgu thai tiflt Ihay ddi thit
thudng ciing tic dflng khdng nhd dfln sin xuit
nflng nghiflp.

Tir hinh 3 cbo thiy cd su chenh lech nhiet dfl

qua kbd bgn, van thich bgp eho viflc san xual nflng
nghiflp neu cd cac bifln phip canh tic hgp ly nhu:
chon diing thdi diflm bat diu mua vu, chgn loai cay
phu hgp cho timg loai dat.
Hinh 4 Ban 6b lu'png mira tmng binh hang nam

Ket qui tdng hgp cae bin dd tren cho thay khu
vgc nghifln ciiu cd the chia thinh bai viing cd
lugng mua ddi lip nhau. Lugng raua Idn d pbia tay
giam dan sang phia ddng theo dg ddc dia binh. Khu
vgc dgc bd bicn, dac biflt tip Irung d cic huyfln
Bac Binh va Tuy Phong (Binh Thuin); Thuan
Nam, Ninh Hii, Ninh San (Ninh Thugn) cd lugng
mua nhieu nim thap, cbi dgt khoang 600mm.
Nguyfln nhin chii yflu dan dfln hifln tugng niy la do
dieu kifln dia binh (khu vgc nay dugc bao quanh
bdi nhting diy nui cao), nhiflt dg dii ven bd khi
cao, khu vgc ngoii khai cd hogt dgng ciia nudc troi
la nhung yflu td gay cin trd mua [4].
368

Mua mu'a va chieu dai thdi gian km ydl:

Tir dQ li^u Iugng mua ngiy cua 6 trgm khi
tugng vi lugng bdc thoit hai tham chilu, chiing tfli
tifln hinh xic dinh chiflu dii thdi gian im udt hing
nam cho tirng tram khi tugng rieng biflt (hinh 6).
Mua mua dugc xac dinh khi lugng raua cao hon
1/2 lugng bdc thoit hai nudc, nhung thdi dilm phu
hgp dfl gieo trdng chi khi lugng mua cao hon

khi dii (thudng tir dau thing 5 den cudi thing 11),
nhung lugng mua trung binh ebi tuong duong vdi
lugng bdc thoat hai nudc, dgc biet thdi gian mua d
day rat that thudng. Hau qua ctia van dfl nay la mac
dil lugng mua irung binh cd thfl dii dfl sin xuat
ndng nghiflp, nhung se tic ddng tiflu cue dfln nang
suit ciy trdng khi khdng cd mua trong vdng
20 ngay.
Tram Bao Ldc l i khu vuc am udt quanh nam,
thdi gian am udl keo dai tu 8 dfln 9 thing, thudng
bai dau vao cudi thing 3, dau thing 4, lugng mua
ting Iheo Ihdi gian v i Ihudng ldn nhit vio d i u
thing 8, lugng mua thudng xuyen cao bon ban so
lugng bdc thoat hai nudc, dieu kifln nay dac biflt

thuan Igi cho sin xuat ndng nghi?p. Trudng hgp
hai tram X u i n L^c va Vung Tau, day ciing la
nhimg khu vgc cd thai gian am udt keo dii. Nhung
do d i e d i l m dja hinh, ranh gidi khu vgc nghifln
ciiu dugc ngan cich bdi nhung day nui cao, do vgy
dac diflm khi h i u am udt ciia B i o Ldc v i Xuin Lgc
khdng anb hudng siu den vimg giihi v i dii ven
biln cua khu vgc nghien ciru. Tuy chi each hai
tram dd vdi khoang cich ngan nhung khi hgu cua
Phan Rang v i Phan Thiet lai mang d i e diem ban
khfl trai ngugc.
3.2. Bdnh gid ndng sudt cdy trong nong

nghifp


2007
Chu thich: dSu (-): thieu dO liflu

Chi4u ddi mua
i m IJM (ngay)


Tir bdng J cd the thiy d khu vuc tram Phan
Thiet xu hudng thay ddi ning suit cay trdng theo
hudng tich cgc. Dd li nang suit ciy trdng giai
doan nim 1994-2007 tang cao han giai doan nam
1980-1994 (tuy ring mirc tang len la khdng nhilu).
Dilu niy cd thi ly giai do lugng mua tir nam 1994
dfln 2007 ting len dang ke va tuong ddi ddng diu
qua eae nim (Idng lugng mua nhimg nam nay
Ihudng ldn hem lOOOnun) vi chilu dai thdi gian
im udt giai dogn nay ciing tang Ifln, cd Ihl ndi ring
lugng mua va chieu dai thdi gian am udt li hai yflu
to quan trgng trong sin xual ndng nghiflp.

Bien difln phin tram nang suit cay trdng ndng
nghiflp theo nim va chieu dai thdi gian im udl
(hinh 7) cho thiy nang suit dugc mfl phdng bang
md hinh Budget li tuong ddi dn dinh trong vdng
30 nam qua ddi vdi trgm Phan Thiflt. Dac biflt giai
dogn hi nam 1994 dfln nim 2007, ning suit ciy
trdng ndng nghiep dao dflng trong khoing 80% khi
trdng tren dit set vi khoing 60% khi trdng tren dit
cat. Nhu da phin tich d tren, xu hudng lich cgc niy
li do lic ddng ting len cua lugng mua vi thdt gian


•
• '

•

•

'
•

1 '''

.

13n

1980

1995

1990

1995

.
3000

iOD5


inh hudng ban dudi tic dflng do sg thay ddi vfl khi
tugng (die biflt sg thay doi vfl lugng mua vi chieu
dii thdi gian am udt).


Tir dd thi biflu difln phin tram nang suit theo
chieu dii i m udt (hinh 7) chung ta cd thfl thay thdi
ky am udt (giai doan ma sd ngiy cd lugng mua ldn
hon lugng bdc thoit hoi nudc P>ETo) keo dii hon
100 ngay la diflu kifln can thiflt dfl dat dugc nang
suit bgp Iy. Thdi ky am udt ngan (cic nam 1982,
1998) tai trgm Phan Thiet va h i u bflt c i c nam tai
tram Phan Rang dflu cho nang suit thap l i nhimg
minh chirng cbo thay hau q u i khi m i chiflu dai sinh
trudng cua ciy trdng khdng phii hgp vdi chiflu dii
thai gian i m udt. Trong ragt sd trudng bgp, nang
suit vin cd the giam vdi giai doan ban ban thit
thudng v i cay trdng tren dit cat nhgy cam ban so
vdi cay trdng trfln dat set dudi tic dgng cua ban
bin v i hoang mac hda.
Lugng mua va chiflu dii thdi gian am udt l i bai
yflu td quan trong anb budng den ning suit cay
trdng nflng nghiep. Tuy nhien, trong mdt sd trudng
bap cdn cd nhung yeu id khac anh budng den nang
suat cay trflng. Chiing ta cd the quan sit thay su
anh hudng cua dieu kien han ban that thudng den
nang suat cay trdng d dd thi bieu dien phan tram

nang suat theo chiflu dai thdi gian am udt ciia trgm
Phan Thilt vao nam 1988 va 2007 (trfln dit set).


31

46 61 76 91 106 121 136 '
Ngay-bat d^utLPl thangS

Elotrmi) 1

jtij

tii

61 76 91 106 121 136 151
Ngdy • bit d^u lir 1 thing 6

Hinh 8 Bieu dfi lu'png mua ngay tram Phan Thiet nSm 1988 v4 2007

Nhin chung, quanh kliu vuc trgm Phan Thilt
lugng raua Irong thdi ky ara udl la du cbo sin suit
dfli vdi nhung eay Irdng ndng nghiflp cd cbu ky
sinh trudng lii tren 100 ngay dfln 160 ngay. Nhung
do lugng raua d day khdng cao hon nhilu so vdi
lugng bdc thoat boi nudc, nen sfl l i kbd tranh khdi
nhung miia vg thit tbu nflu khdng xic dmh chinh
xic ngay bat dau miia vy. Han niia, day la khu vgc
cd difln tich dit cit cbiflm dien ticb khi ldn, Ii logi
dat cd khi nang tham v i thoat nudc rit nhanh, vi
vay can cd nhiing bifln phip thuy Igi bgp ly hd trg

372

cay trdng ndng nghiep, chieu dai thai gian im udt
Uen 100 ngiy la yeu cau cin thilt.
(ii) Danh gia miic suy giim ning suit cay trflng
nflng nghiflp ngan ngiy
Dfli vdi nhQng khu vgc khd hgn bay bin khd,
ciy ndnp nghiep dugc trdng Iren dit set ludn cd
ning suit cao ban nhiflu so vdi eay trdng tren dil
cat. Die biflt ddi vdi nhQng viing cd lugng mua
ludn thit Ihudng nhu Phan Thilt thi nang suit cay
ndng nghiflp dugc trdng tren dit set tuong ddi
fln djnh.

dau gieo trdng thich hgp cho khu vgc tinh Binh
Thugn thudng vio diu thing 5 hang nam vi diu
thing 9 cho tinh Ninh Thuin.
Ddi vdi khu vuc Phan Rang, noi cd lugng mua
thap vi chiflu dai thdi gian im ngan, ciy trdng
nong nghiep chi cd the dat nang suit cao khi ed sg
hd trg tir he thdng thiiy lgi, ddng thdi xac dinh
dung tbdi diflm gieo trdng.
Xiy dgng cac hd du tru nudc li cdng viee quan
trpng dfl giam thieu nhQng rui ro thoai bda dat do
hoang mac bda vi xim nhap man, dac biet li viec
nit ngan thdi ky im udt do tic ddng ciia bifln ddi
khi hau.
TAILIEUDAN
[I] Dirk Raes. 2002: BUDGET A soil water
and salt balance model.
[2] Jensen. M. E, 1968: Water consumption by
agricultural plants. Chap 1 in Water Deficits and