AlVH HUOIVG CLIA LIEU LLTOIMG V A THOI DIEIIi BOIM DAIVI DEIXI IXIAIXIG S U A T V A
H A M ILLIOIXIG IXIITRAT
TROIXIG RALI CAI XAIVH V A X A
L A C HT A I
T I I X I HTHIJA THIEIM - H U E
Hodng TTii TTidi Hda*, Nguyin Do''
T6MTAT
Thi nghidm dupc thue hi$n trong nam 2009 - 2010 tai huyf n Huong Tra, tinh Thira Thi6n - Hue, gdm c6 2 ylu td la 5 liiu lupng dam (0, 30, 60, 90 va 120 kg N/ha) va 2 thdi diim bdn (trudc thu hoach 15 ngay vd 7 ngay), thi nghidm dupc bd tri theo kilu split - plot (chia 6) vol 3 lan nhdc lai. Kit qua nghidn ciiu cho thdy thoi diim bon d?m va liiu lupng bon co anh huong din mpt sd chi tifeu sinh trudng ciia rau cai xanh va xd lach nhu thdi gian sinh trudng, chiiu cao cdy, sd Id, dudng kinh tan. Nhin chung cac chi tiSu nay dat cao nhat khi bon vdi liiu luong dam 90 kg N/ha va 120 kg N/ha. Ham lupng NGj" trong rau cai xanh vd xa lach d cac cong thiic tang l6n tuong iing voi lieu lupng dam dugc bon tSng Ifen. Nang sudt rau cai xanh va xd Idch dat cao nhat d cong thiic bon 120 kg N/ha va 90 kg N/ha. Ham lupng NOjdat cao nhdt d cong thiic bon 120 kg N/ha ddi voi ca hai loai rau va vupt muc cho phep d thdi diem bdn trudc thu hoach 7 ngay. Thdi diim bon dam ket thiic trudc thu hoach 15 ngay co ham lupng NO3 frong rau thap hon so vdi kit thiic trudc thu hoach 7 ngay d tat ca cac lieu luong darn bon.
Tir khoa: Ham luang nitrat, lieu luong dfmi, nang suit, rau, thai diim bon dam.
LDATVAND^
Trong qud trinh sinh trudng vd phdt triln ciia cdy trdng, dam Id mpt trong nhiing yeu td dinh dudng co ban cdn thilt Nd tham gia vdo vile cdu thdnh cdc chat liiu di truyin vd protein cung nhu cdc thdnh phdn chu ylu khdc cua t l bdo thue vdt Khi cung cdp khing dii hdm lupng dam can t h i l t qud trinh sinh tnrdng vd phdt triln cua cdy trdng se bi han chi hodc bi ngung tri hodn todn (Nguyin Vdn Bp, 1997). Tuy nhiln vdi nhu cdu san xudt rau tdng nhanh, thi nhirng lo ngai vl sir an toan ciia san phdm rau ciing ngdy cdng tdng, ddc biit Id vile sii dung mdt lupng ldn phdn bdn trong dd cd dam cho m6t diln tich trdng rau nhd, d nhirng viing trdng rau cd trinh dd thdm canh cao, noi dang cd gdng d l fhiic ddy tdng san lupng rau. Nhirng nghiln ciiu gdn ddy cho thdy nhilu mdu rau cd ham lupng NO3" vupt qud ngudng cho phep ciia td chiic Y t l till gidi (WHO) toi 3-5 ldn.
Mpt sd kit qua thu nghilm ciing cho thdy cd su tuong quan giiia vile bdn phdn dam va lupng nitrat tich tii ti-ong ning phdm ff)udng Hdng Dat, 2003).
Bien phdp hiiu hieu nhdt hiln nay d l giam lupng nitrat tdn dpng trong nong phdm Id sii dtmg mpt chi Khoa Tai nguyen Dat va MTNN Trudng DH Nong Lam Hue
^ Khoa Nong hpc - Tnrdng Cao ddng Ky thu^t Nong Lam DaL^it
dp phan bdn hpp ly. Do dd cdn phai cd cdc ddnh gik v l ham lupng NO3" trong rau, mdi quan h i giira sir dtmg phan dam vdi chiing vd ndng sudt, lam co sd cho vile d l xudt cdc biin phdp quan ly dinh dudng nhu xdc dmh dupc qui trinh phdn bdn cdn ddi vd hpp ly cho cdy rau Id hudng nghiln ciiu chinh cua dl tai ddt ra. Xudt phdt tir nhiing ly do trin dd tiin hdnh thue hiln d l tdi vdi cdc muc dich sau:
- Xdc dinh anh hudng ciia liiu lupng dam vd thdi diim bdn dam din ndng sudt rau cai xanh vd rau xd Idch.
- Xdc djnh anh hudng ciia liiu lupng dam vd tiidi diim bdn dam din ham lupng NO3" trong rau cai xanh vd rsu xa Idch.
- D l xudt biin phdp sii dung phdn bdn hpp ly cho rau cai xanh va rau xd lach.
I . VAT L P VA PHUONG PHAP NGHIBV CUU 1. Ddi tupng nghiln cuu
- Ddt Nghiln ciiu dtrpc tiin hanh trin ddt phii sa dupc bdi hang ndm chuyin trdng rau. Mpt sd tinh chdt hda hpc cua ddt trudc thi nghilm nhu sau: PHRO
(4,51), OC (1,23%), N (0,066%), P2O5 (0,050%), K2O (0,24%).
- Cay trdng: Rau cai xanh (gidng dja phuong) va rau xd lach (gidng 2 mui tin) Id cdc gidng dang dupc trdng phd biin tai dia phuong. Mat dd trdng rau cai 30 NONG NGHIEP VA PHAT TRIEN NONG THON KY 1 - THANG 9/201 1
KHOA HOC C 6 N G NGHfi xanh Id 25 cdy/m^ (khoang each 20 cm x 20 cm), mdt
dd trdng rau xd Idch Id 30 cdy/m^ (khoang cdch 18 cm X18 cm).
Phdn bdn; Dam urI (46%N), ldn supe (16,5%
P2O5), KCl (60% K2O), phdn chudng, voi bpt 2. Dja diim vd thdi gian nghidn ciiu
Thi nghilm dupc tiin hdnh tai xd Huong An, huyIn Huong Trd, tinh Thira Hiiln Hul trong hai
vu ddng xudn (tiidng 12/2009 din tiidng 2/2010) vd xudn he (tiidng 3/2010 din tiidng 5/2010).
3. Phuong phdp nghiln cihi a. Cdng thue thinghiim
Thi nghilm gdm 10 cdng thiic vdi 2 ylu td: dam (5 liiu lupng: 0,30,60,90,120 kg N/ha) vd tiidi diim bdn N (kit thiic trudc thu hoach 15 ngdy vd 7 ngdy).
CT 1 2 3 4 5 6 7 8 9 10
Thdi diim bdn N trudc thu hoach (ngdy)
15 a i ) 15 a i ) 15 a i )
15 (TD 15 (Tl)
7(T2) 7(T2) 7(T2) 7(T2) 7(T2)
Bdng 1. CIng thue thi nghi|m Phdn chudng
(tan/ha)
15 15 15 15 15 15 15 15 15 15
N (kg/ha)
0 30 60 90 120
0 30 60 90 120
P2O5 (kg/ha)
30 30 30 30 30 30 30 30 30 30
K2O (kg/ha)
60 60 60 60 60 60 60 60 60 60
Vdi (kg/ha)
500 500 500 500 500 500 500 500 500 500 Thi nghilm bd tri theo kilu split - plot (6
ldn vd 6 nhd), trong dd thdi diim bdn dam bd tri trin 6 ldn vd liiu lupng dam bd tri trin 6 nhd, vdi ba ldn nhdc lai. Di|n tich mdi 6 nhd Id 5 m^vd diln tich mdi 6 ldn Id 50 m l
b. Biin phip ky^ thuat ip dung cho thinghiim - Bdn phdn:
+ Bdn Idt todn b6 voi, phdn chudng vd phdn ldn vd kali cho tat ca cdc c6ng thiic.
+ Bdn thiic ldn 1 sau trdng 5 ngdy vdi 50% lupng phdn dam urI.
+ Bdn thiic ldn 2 kit thiic trudc thu hoach 15 ngdy vd 7 ngdy vdi 50% lupng dam cdn lai cho tdt ca cdc cdng thirc.
- Cdc bi|n phdp ky thudt khdc dp dung theo qui trinh chung cho cdy rau cai xanh vd xd Idch.
c. Cic chi tiiu theo ddi
- Cdc chi tiiu vl sinh tnrdng ciia cdy: Thdi gian sinh trudng vd phdt triln ciia rau, chiiu cao cdy, sd Id, chiiu ddi Id, chiiu rdng Id, dudng kinh tdn cay.
- Cdc chi tiiu vl ndng sudt Ndng sudt ly thuylt ndng sudt sinh vdt (khdi lupng todn bd than Id, r l ) .
ndng sudt kinh t l (khdi lupng phdn dn dupc).
- Cdc chi tiiu vl phdm chdt rau: Hdm lupng NO3 trong rau phdn tich theo phuong phdp so mdu trin quang phd kl.
d. Phuang phip xir lys6 liiu
Cdc sd li|u thu thdp dupc xtr ly thdng k l t r i n phdn m i m Statistix 9.0 v l cdc chi tiiu nhu triing binh, phdn tich ANOVA, LSD, Duncan phdn tich tuong quan.
1. KET QUA NGHiN CUU VA IHAO LUAN
1. Anh hudng ciia liiu lupng d^m vd thdi d i i m bdn d^un d i n mdt sd chi tiiu sinh trudng ciia cdy rau cai xanh vd xd Idch
a. Rau cai xanh
Kit qua nghiln ctiu trinh bdy d bang 2. Thdi diem bdn dam cd anh hudng khd rd rlt din thdi gian sinh tnrdng ciia rau cai xanh. Nhin chung thdi gian sinh tnrdng dupc nit ngdn hon 1 2 ngdy khi bdn dam kit thiic sdm trudc thu hoach 15 ngdy so vdi kit thiic trudc thu hoach 7 ngdy d cdc liiu lupng dam bdn tir 30 - 120 kg N/ha, diiu dd cho tiidy tiidi diim bdn dam dd cd tdc ddng din thdi gian sinh tnrdng cay cai xanh.
NONG NGHlfP VA PHAT TRIEN N O N G T H C N - KY' 1 THANG 9/2011
31
Bdng 2. Anh hudng cua liiu lupng d^un vd tiidi diim bdn d^m din thdi gian sinh trudng vd mOt sd chi tiiu
C d n g thiic T,N„
T,N3o T,N«, T.N«o TiN,2o
T.N„
'•Ti,N^
Ti-Nfio T2N30
TzNizo LSDocs
TG sinh trudng (ngdy)
58'' 59'' 59'' 60'=''
62'' 59'' 60°' 61 cd 61^''
6 4 ' 1,28
sinh tnrdng t Chiiu cao
cdy (cm) 27,57^
30,59'''=
33,77=*
33,03 * 35,02"
27,95'=
33,11 =*
33,03 •*
33,83 =>
35,99^
3,23
ldn Id cua rau cdi xanh Sold
(cm) 8,60'=
8,73^
8,87^
9,33 =•'"=
10,07"
8,67^
9,13''^
9,27''^
9,73"'' 9,87»'' 0,75
C h i i u ddi Id (cm) 26,63 fe 30,46°'^
32,15 "^
33,71 =*
34,86"
25,59 « 27,37 ^ 29,19 ''^
31,08 '^'^
32,69 »'"=
3,32
Chiiu rdng Id (cm) 14,75 "I 17,19'"=
17,64 "^
18,08 * 18,24"
14,67'' 17,01' 17,27 ''"=
17,95 =>'"=
18,19 =*
1,00
D u d n g kinh tdn (cm)
27,10 = 33,12 =*
33,83 ^ 34,88=*
3 5 , 1 6 "
26,70 = 31,45'' 32,87=*
33,93 =•'' 34,97"
3,44
(Ghi chu: Cic cdng thiic tiong cimg mdt cdt cd cung mdt ky tu biiu tiii khdng cd su sai khic y nghia d muca = 0,05). TG: thdi gian. SSliiu bang tiin dugc tinh trung binh tir hai vu tiong ddng xuan vi xuan hi
Kit qua bang 2 ciing cho thdy thdi gian sinh trudng d cdc cdng thiic bdn dam cd su sai khdc cd y nghia thdng kl so vdi cdng thiic ddi chiing (khdng bdn dam) d ca hai thdi diim bdn, nhin chung thdi gian sinh tnrdng tir khi gieo trdng din khi tiiu hoach cua cdc cdng thiic dupc bdn dam dao dpng tir 59 - 64 ngay tai ca hai thdi diim bdn dam.
Ddi vdi cdc chi tiiu sinh trudng cdn lai, cd su sai khdc thdng kl giira cdc lieu lupng dam bdn trong cimg mpt thdi diim bdn, nhung it cd su sai khdc giiia mpt lupng dam bdn tai hai thdi diim bdn. Chiiu cao cay tdng lln khi tdng liiu lupng dam bdn cho cai xanh vd cdc cdng thiic cd bdn phdn dam diu cd chiiu cao cdy cao hon mdt each cd y nghia so vdi ddi chiing (khdng bdn dam). Su sai khdc ndy thi hiln ro khi bdn vdi liiu lupng dam Id 90 vd 120 kg N/ha. Kit qua ndy tupng tu nhu kit qua nghiln ciiu ciia Pham Minh Tdm (2001) vdi rau cai be xanh trin nin ddt xdm. Sd Id d cdc cong thiic thi nghilm tdng lln khi tdng hlu lupng dam tir 30 120 kg/ha. Vdi nhiing cdng tiiiic dupc bdn 90 hodc 120 kg N/ha thi cd sd la dat trung binh khoang 10 la, trong khi cdng thiic bdn
ngdy cd thdi gian sinh tnrdng dupc nit ngdn hon 1 ngdy so vdi thdi diim bdn dam trudc thu hoach 7 ngdy. Thdi gian sinh tnrdng trung binh tai thdi diim bdn dam kit thiic trudc thu hoach 15 ngdy la 55 ngdy, trong khi dd d thdi diim bdn sau dd la 56 ngdy.
Diiu nay chiing td rang vile bdn dam kit thiic sdm hay muon da anh hudng din thdi gian sinh trudng ciia rau xd Idch vd rat cd y nghia tiitrc tl trong vile chpn thpi diem bdn dam thich hpp. Ddi vdi cac chi tiiu sinh tnrdng khdc khdng thdy cd str sai khdc vl mdt thdng kl giira hai thdi diim bdn dam b-ln ciing mpt lupng dam bdn.
Tai cimg mdt thdi diim bdn dam, nhung liiu lupng dam khac nhau tiii tiidi gian sinh trudng d cdc cdng thiic cd bdn dam ddi hon khoang 1 - 6 ngdy so vdi cdng tiiiic ddi chiing. Trong khi dd thdi gian sinh trudng d cdng tiiiic bdn 60 kg N/ha vd 90 kg N/ha cd str sai khac vd dai hon 1-2 ngdy so vdi liiu lupng dam bdn 30 kg N/ha vd 0 kg N/ha. Chiiu cao cdy d cdc cdng tiitic cd bdn dam dao dpng khoang tii 23,63 26,27 cm.
Trong dd chiiu cao cdy dat cao nhdt khi bdn vdi liiu lupng dam 90 kg N/ha va 120 kg N/ha vd tiimg binh phdn dam tiidp hon (30 va 60 kg N/ha) chi d?it tiung ^^ ^^ khoang 5 - 6 cm so vdi cdng tiiiic ddi chiing.
Sd Id tdng lln d cdc cdng thiic cd bdn dam khoang tir 18 - 20 Id. Lupng dam tdng khdng chi lam tdng vl sd Id/cdy ma cdn anh hudng cd y nghia din chiiu ddi la, chiiu rdng Id. Khi xem xet 2 chi tiiu ndy dd tim tiidy su khdc biit rat rd giira lupng dam bdn 60 kg N/ha, 90 kg N/ha vd 120 kg N/ha so vdi 30 kg N/ha.
Tuong ttr nhu vdy ddi vdi chi tiiu dudng kinh tdn Id, khi tdng Ulu lupng d^m bdn thi dudng kinh tdn tdng binh 9 Id/cdy. Kit qua cho tiiay, dudng kinh tan ciia
rau cai xanh dat trin 32 cm d tdt ca cdc lieu lupng dam bdn vd uu thi van tiiupc vl nhiing cdng thiic cd bdn dam nhilu hon.
b. Rau xa lich
Kit qua d bang 3 cho tiidy vdi ciing mdt lupng dam bdn, nhung thdi diim bdn dam trudc thu hoach 15
32 NONG NGHlf P VA PHAT TRIEN NONG
THON- KY 1 - THANG 9/2011
KHOA HOC
C 6 N GNGHfi
l l n , dudng kinh tdn dat t r i n 25 cm d tdt ca cdc cdng ciing tiiupc v l cdc c6ng thiic cd bdn dam cao hon tai thiic dupc bdn phdn dam, vd nhdm c h i l m uu t h i ciing mpt thdi d i i m bdn dam.
Bang 3. Anh hudng ciia liiu lupng d^un vd thdi d i i m bdn d^m d i n thdi gian sinh trudng vd mdt sd chi tiiu sinh trudng thdn Id ciia rau xd Idch
Cdng thiic T,No T.N^o T,N«„
T,N«, T1N120
T,N„
T2N30 T2N60 T2N90 T2N,2o LSDo.05
TG sinh tnrdng (ngdy)
5 3 ' 54"=
55'' 56 = 5 9 ' ' 54*
5 5 ' ' 5 5 ' ' 56 = 60=' 0,96
Chiiu cao cdy (cm)
20.93'' 23,63 = 24,13 •'=
24,53 ''=
26,03' 20,93'' 23,70 = 24,37 ''=
25,53 =">
26,27 =>
1,40
Sdld (cm) 17,67'' 18,93 ="''
19,53 =>
20,47"
19,73"
17,73'' 18,87 ='''
19,67 =•
20,33"
19,47 =•
1,60
Chiiu ddi Id (cm) 16,97'' 19,80''=
20,21 =*=
21,10"
20,43 "''=
17,13 •' 19,69 = 20,40 ""=
20,87 =''' 20,19 "''=
1,09
Chiiu r i n g Id (cm)
11,47 = 13,91'' 14,63"'' 15,10 =•
14,59 =•'' 11,80 = 13,99"
14,69 =''' 14,97 =•
14,73 =*
0,88
Dudng kinh tdn (cm)
20,93 = 25,47'' 25,83 =*
27,07"
26,40"'' 20,80 = 25,90"'' 26,03"'' 27,13"
26,10"'' 1,38
(Ghi chu: Cic cdng thdc tiong cung mdt cdt cd cung mdt ky tu biiu thi khdng cd su sai khic y nghia a muca = 0,05). Si liiu bang tiin dugc tmh trung binh tir hai vu tiong ddngxuin va xuan he.
2. Anh hudng d i a liiu lupng d^un vd thdi d i i m bdn dam d i n ndng sudt rau cai xanh vd xd Idch
a. Rau cai xanh
Bdng 4. Anh hudng ciia lilu lupng d^m vd thdi d i i m bdn dam d i n ndng sudt rau cdi xanh Cdng
thirc T,No T,N,„
T,N«, T,N«, T1N120 T,Nn
TjNjo TjNfio T2N90 T2N,20 LSD005
Ndng suat ly thuylt (tan/ha)
31,26' 34,55"' 35,59 ="'
37,22"
38,82"
31,59 • 34.25' 34,69 "=
35,63 ='' 36.84 "=
1,58
Nang suat sinh vat (lan/ha) 26.88"' 29.04 "=
31,07""
31,57»
32.77"
25,55*
28.72 ="
30,77""
31,02""
31,18""
2,27
Nang suat kinhtl (tan/ha)
22.21 * 26,24 ="
27,85"
28,98""
29,73"
21,55*
25.36"
27.75 "=
27,39 "=
28.12""
1.86 (Ghi chu: Cic cdng thue tiong cung mdt cdt cd cung mdt kytu biiu tiiikhdngcd su sai khic y nghia a muca = 0.05). Sd' lieu bang tiin dugc tinh trung bmh tir hai vu tidng ddngxuin va xuan he.
K i t qua phdn tich tiidng k l cho thdy cdc chi tiiu v l ndng sudt cua rau cai xanh (ndng sudt ly t h u y l t ndng sudt sinh v d t ndng sudt kinh t l ) khi bdn ciing lupng dam t ^ hai thdi d i i m khdc nhau thi khdng cd sir sai v l mdt tiidng k l , chi cd sir sai khac giira cdc lupng d^m bdn tai ciing mdt tiidi d i i m bdn (Bang 4).
K i t qua d bang 4 cho thdy:
- Ndng sudt ly thuylt: Ndng suat ly thuylt d cdc cong thiic cd bdn dam dao dpng khoang tir 31 - 39 tan/ha tai thdi diim bdn dam kit thiic trudc thu hoach 15 ngdy vd 32 - 37 tan/ha tai thdi diim bdn dam kit thiic trudc thu hoach 7 ngdy. Ndng sudt ly thuylt cd sir khdc biit rdt rd giiia lilu lupng 120 kg N/ha so vdi lupng dam 30 - 60 kg N/ha khoang 1 - 2 tan/ha.
- Ndng sudt sinh vdt vd ndng suat kinh t l : Cd sir sai khdc rdt rd giira cdc cdng thirc bdn 120 kg N / h a so vdi 30 kg N / h a khoang 3 tan/ha. Tuy nhiln khdng tim thdy su sai khdc giua lupng dam bdn tir 60 - 1 2 0 kg N / h a ddi vdi hai chi tiiu ndy. Diiu ndy cung t h i h i | n qua str phdn tich mdi tuong quan giira ndng sudt sinh vdt vdi lilu lirpng dam bdn cho cdi xanh cho thdy cd mdi quan h i phi tuyIn tinh chdt vdi h i sd xdc d}nh R^ = 0,99. Tir dd chiing td ndng sudt cai xanh tdng cimg vdi lilu lupng dam tdng lln tir 30 - 120 kg N / h a , hiy nhiln d lupng bdn 120 kg N / h a ndng suat cd xu hudng khdng tdng niia.
C i i xunh
- 0 . 0 0 0 4 x ^ +
6 0
O.IOU2X 0 . 9 9 0 1
9 0
+• 2 6
1 2 0 2 6 3
Hinh 1. Tuong quan giira lilu lupng d^m vd ndng sudt sinh v^t ciia rau cdi xanh
NONG NGHIfP VA PHAT TRIEN NONG
T H 6 N- KY 1 THANG 9/201 1 33
b. Rau xa lich
Tuong tu rau cai xanh, k i t qua phan tich thdng k l cho thdy khing cd sir sai khdc cd y nghia khi bdn ciing mdt lupng dam bdn tai hai thdi diim bdn khdc nhau vl cdc chi tiiu ndng suat ciia cdy xd Idch. Sir sai khdc ndy chi dupc tim thdy khi bdn dam vdi cdc Hlu lupng khdc nhau (Bang 5).
Bang 5. Anh hudng ciia lilu lupng dam vd thdi diim bdn dam d i n ndng sudt rau xd
Cdng thiic T,N„
T1N30 TiNeo T,N9o TiN,2o
T,N„
T2N30 TzNeo T2N90 T2N,2o LSDo.05
Ndng suat ly thuyet
(tan/ha) 23,48 = 29,04 ''=
31,07 "*>
31,57"'' 32,77"
21,55 = 28,72 ''=
30,77"'' 31,01 "i- 31,17 ">>
3,59
Nang suat sinh vat (tan/ha) 18,78 = 23,68='' 24,94 •>
28,08"
27,08'' 17,95 = 22,51'' 24,78 ''=
27,32"'' 26,82 *>
0,95
dch
Nang sudt k i n h t l (tan/ha)
14,68' 18,04*
20,14="
23,89"
22,27'' 13,74' 18,82 ''*
20,16 = 22,40'' 22,11'' 1,46 (Ghi chu: Cic cdng thiic tiong cung mdt cdt cd cung mdt ky tu biiu thi khdng cd su sai Ichic ynghia a muca - 0,05). Sd lieu bang tiin dugc tinh trung binh tir hai vu tiong ddngxuin va xuan he.
Kit qua d bang 5 cho thay:
Ndng suat ly thuyet d cdc cdng thiic cd bdn dam dao dpng tir 29 - 33 tan/ha tai hai thdi diim bdn dam khdc nhau, cao hon so vdi ddi chiing khoang 6 - 9 tan/ha. Trong dd ndng suat ly thuylt dat cao nhdt d cdng thiic bdn 90 kg N / / h a va 120 kg N/ha vd thdp nhat d c6ng thirc dupc bdn vdi lilu lupng 30 kg N/ha. Tuy nhiln khdng cd sir sai khac cd y nghia vl ndng suat ly thuylt vdi lilu lupng dam bdn tir 60 -
120 kg N/ha tai ca hai thdi diem bdn dam.
Ndng suat sinh vdt Cd sir sai khdc cd y nghia khi bdn dam vdi cdc lilu lupng khdc nhau. Ndng sudt sinh vat dat cao nhdt d cdng ihtic 90 kg N/ha va 120 kg N/ha. Tuy nhiln khdng cd str sai khac giiia hai cdng thirc nay. Ndng suat sinh vat ciia cpng thiic 120 kg N/ha cd xu hudng giam xudng so vdi lupng dam bdn 90 kg/ha tai ca hai thdi diem bdn dam.
- Ndng suat kinh tl: Nhin chung ndng sudt kinh t l trung binh dat khoang tii 14 - 24 tan/ha. Trong dd
ndng sudt kinh t l dat cao nhat 0 cac d thi nghilai dupc bdn vdi Ulu lupng 90 kg N/ha, va thap nhat 6 cdng thiic 30 kg N/ha. Bin canh dd ndng sudt kinh t l cd stj sai khdc giira cdc cdng thiic. Tuong ttr ndng sudt sinh vat, ndng suat kinh t l khi lupng bdn 120 kg N/ha thap hon cd y nghia so vdi lupng bdn 90 kg N/ha tai thdi diim bdn dam k i t thiic trudc thu hoach 15 ngdy, nhtmg khdng sai khdc cd y nghia tai tiioi diim bdn dam k i t tinic trudc thu hoach 7 ngdy.
3 0
% 2 0 1 0
0 -
<
XA l i c h
y = -0.<)<)0«x^ -1- 0. Ifi7x + 1 8 . 4 1 7 R^ = 0 . 9 «
N Cku/Ul) ) 3 0 6 0 9 0 120
Hinh 2. Tuong quan giiia lilu lupng dam vd ndng sudt sinh vdt ciia rau xd Idch
Cung tim thdy cd su tuong quan giira ndng su^t sinh vat va lupng dam bdn cho cho rau xd Idch. Day Id tuong quan phi tuyIn tinh chdt vdi he sd xac dinh R^ = 0,98. Diiu nay cd t h i chiing td rdng ndng suat ciia xd lach bdt ddu cd xu hudng giam khi lilu lupng dam bdn vupt qua ngudng 90 kg N/ha.
3. Anh hudng ciia lilu lupng dam vd thdi diim bdn dam din hdm lupng nitrat trong rau cai xanh v4 xdldch
Chat lupng la mpt trong nhirng chi tiiu quan trpng lu6n dupc chii y hang ddu trong vile tiiu thii rau trin thj tnrdng, nin nd ciing Id mdt trong nhirng nhan td hang ddu thiic ddy san xuat rau phdt triln.
Kit qua thi nghilm thi hiln 0 bang 6.
Bang 6. Anh hudng ciia lilu lupng d^m vd thdi diim bdn dam din hdm lupng nitrat trong rau cai xanh
vd xdldch Cdng thiic
T,N„
T,N^
T,N«, T,N^
riN,2o T,No TjNao T2N60 T2N90 I2N120
Ham lupng nitrat (mg NOj/kg) Rau cai xanh
122,0 322.4 365,1 677,0 925,5 250,2 452,4 775,8 777,0 1137,2
Rau xd lach 144.7 245,2 303.2 398.6 1103.8
195,5 252.5 565,0 797,1 1543,4 Ngudn: Kit qua phin tidi, ndm 2010.
34 NONG NGHIEP VA PHAT TRIEN NONG THON - KY 1 THANG 9/2011
KHOA HOC C 6 N G NGHfi
Bdn dam trudc thu hoach 15 ngdy: Kit qua phdn tich cho thdy hdm lupng nitrat d cdc cdng thiic tdng tuong iing vdi Ulu lupng dam dupc bdn tdng.
Nhin chung hdm lupng nitrat d cac cdng thiirc cd bdn dam dao ddng tir 322,4 - 925 mg NO3 / k g (cdi xanh) vd 245,2 1103,8 mg NOj/kg (xd Idch). Hdm lupng NO3 dat cao nhdt 0 cdng thiic bdn 120 kg N/ha ddi vdi cd hai loai rau. Nhu vdy vdi Ulu lupng bdn ndy dd ldm cho rau cdi xanh cd hdm lirpng NO3" vupt mtic cho phip ddi vdi tiiu chudn rau an todn quyit dinh bdi Bd Ndng nghilp va Phdt triln ndng thdn (2006).
Bdn dam trudc thu hoach 7 ngdy: Ciing thu dupc kit qud tuong tu. Hdm lirpng nitrat trung binh d cac cdng thiic cd bdn dam ciia cay cai xanh dao dpng toi 452,4 - 1137,2 mg NOj/kg, vd tdng khoang 200 - 880 mg NOs/kg so vdi cdng thiic ddi chiing. Tuy nhiln khi tiin hdnh so sdnh vdi hdm lupng nitrat tiiu chudn thi ham lupng dam trong rau cdi xanh virpt mtic cho phep khoang tir 237 mg NOs/kg. 6 cdy xd lach hdm lupng nitrat dat cao nhdt 0 cdng thiic dupc bdn dam vdi Ulu lupng 120 kg N/ha.
- Kit qua phdn tich cho thdy khi tiin hdnh bdn ciing mdt Ulu lupng dam nhu nhau tai 2 thdi diim bdn khdc nhau thi hdm lupng nitrat cd sir chinh lich rdt rd. Nhin chung d cdc cdng thiic dupc bdn dam vdi ciing lilu lupng dam nhu nhau tai tiidi diim bdn trudc thu hoach 7 ngdy cd hdm lupng nitrat cao hon nhilu so vdi vile bdn dam tai thdi diim bdn trudc thu hoach 15 ngdy. Diiu ndy chting td rdng thdi diim kit thiic bdn dam trudc thu hoach da anh hudng ddng k l din hdm lupng nitrat trong rau. Tir dd lam co sd cho vi|c chpn mdt thdi diim bdn dam thich hpp cho rau cai xanh vd rau xd Idch.
Mdi quan h | giira ham lupng nitrat trong rau cai xanh vdi Ulu lupng dam dupc bdn tai hai thdi diim khdc nhau dupc xdc dinh. Ddy Id mdi tuong quan tuyIn tinh chdt vdi h | sd xdc djnh tirong iing Id R2 = 0,95 vd R2 = 0,94 (Hinh 3). Qua su phdn tich ndy tiidy rd dupc hdm lupng nitrat tdng lln khi tdng Ulu lirpng dam bdn vd dat cao nhdt d Ulu lupng dam 120 kg N/ha. Trong tiiuc t l san suat vi|c chpn mpt thdi diim bdn tiiich hpp (Tl) vdi mpt lilu lupng bdn hpp ly s i Idm tdng ndng sudt vd phdm chdt ciia rau.
Tirong tor nhu vdy, cd str tuong quan khd chdt giiia lilu lupng dam vdi hdm lupng NO3" trong rau xd lach tai hai thdi diim bdn vdi h i sd xdc dinh tirong ung R2 = 0,73 vd R^ = 0,88 (Hinh 4), diiu ndy hoan
todn phii hpp vdi nhilu kit qua nghiln ctiu trudc ddy (Biii Quang Xudn vd cs, 1996).
?
b^
10001 800 - 800 - 400 200 0
C
R a u c i i x a n h ( T l )
•
^ 5 = 6.532X + 9 0 . 8 8
•- R^ = 0 . 9 5 3 3
) 30 60 90 120 N ( k g / h a )
Rau cAI xanh (T2)
30 60 N(kg/ha)
Hinh 3. Tuong quan giira Ulu lupng dam vd hdm lupng NO}' trong rau cdi xanh tai hai thdi diim bdn
^
) 0 0 0 0 0 0
R a u x a l a o h (T1)
y = e.gosax + 2.4.78 R* = 0 . 7 3 2 1
} 30 eo N ( k g / h a )
•
SO
•
120
i
^
2000 n 1500 1000 500 0
(
R a u x& lAch (T2)
y = 10.801X + 2 2 . 6 2
R 2 = 0.8828 ^^_.^
!—.—*'****'^
> 30 60 80 N ( k g / h a )
•
120
Hinh 4. Tuong quan giiia Ulu lupng d^m vd hdm lupng NO}' trong rau xd Idch t^i hai thdi diim bdn
Nhu vdy khi tdng Ulu lupng dam bdn tai hai thdi diim khdc nhau diu ldm tdng sti tich liiy dam trong rau xd Idch, dupc thi hiln 0 ca hai thdi diim bdn ddc biit d lupng dam tir 90 din 120 kg N/ha. Vd tai tiidi diim bdn trudc tiiu hoach 15 ngdy su tich luy ham lupng nitrat trong rau xa Idch giam mpt cdch ddng k l so vdi bdn tai thdi diem trudc thu hoach 7 ngdy. Do dd, cdn phai chpn thdi diim bdn trudc thu hoach 15 ngdy kit hpp vdi lilu lupng dam bdn thich hpp d l nhdm ndng cao ndng sudt vd phdm chat rau.
N 6 N G NGHIEP V A PHAT
TRIEN
N 6 N GTHON KY 1 - THANG 9/2011
35IV. KET LUAN VAD£ NGHI
Thdi gian sinh trudng ciia rau cai xanh vd xd Idch dupc nit ngdn khi bdn dam k i t thiic sdm trudc thu hoach 15 ngdy. Tdng Ulu lupng dam l l n d i n 120 kg N/ha thi thdi gian sinh trudng keo ddi so vdi cdng tinic khdng bdn dam tai cimg mpt thdi diim bdn dam.
Bdn phdn dam d thdi diim trudc liic thu hoach (15 ngdy) cho thay rd hiiu luc cua phdn dam ddi vdi cac chi tiiu sinh tnrdng ciia cdy rau cai xanh vd xd lach so vdi bdn ciing lilu lupng dam d thdi diim sau dd. Chiiu cao cay tang lln khi tdng Ulu lupng dam bdn va dat cao nhdt d cdc cdng thiic cd bdn 90 vd 120 kg N/ha.
Ndng sudt rau cai xanh dat cao nhdt d cdng thiic bdn 120 kg N/ha, nhung khdng cd sir sai khac giira Ulu lupng dam bdn tir 60 -120 kg N/ha. Ndng sudt rau xd lach dat cao nhat d cdng thirc bdn 90 kg N/ha vd cd xu hudng giam xudng khi lupng bdn 120 kg N/ha.
- Ham lupng NO}' trong rau cai xanh vd xd Idch d cac cdng thiic tdng lln tirong ting vdi Ulu lupng dam dupc bdn tdng lln. Ham lupng NO3 dat cao nhat d cdng thiic bdn 120 kg N/ha ddi vdi ca hai loai rau vd vupt mtic cho phep 0 thdi diem bdn trudc thu hoach 7 ngdy.
Thdi diim bdn dam kit tiiiic trudc thu hoach 15 ngdy cd ham lupng NO3- trong rau tiiap hon so vdi kit thiic trudc thu hoach 7 ngay d tat ca cdc Ulu lupng dam bdn.
Budc ddu d l nghi bdn 60 - 90 kg N/ha cho rau cai xanh vd xd Idch trin nin bdn 30 kg P2O5, 60 kg K2O, 500 kg vdi va 15 tan phdn chudng/ha se thu dupc ndng sudt, phdm chdt vd hiiu qua kinh tl tot nhdt Nin bdn dam vdo thdi diim kit thiic tiirdc thu hoach 15 ngdy se dam bao ham lupng NO3" trong rau khdng vupt mtic cho phep.
TAIUEUTHAMKHAO
1. Nguyin Vdn Bp, 1997. NhOng nguy ca 6 nhiim mdi trudng tir phan bdn. Hdi thao: Phdn bon vd mdi tiirdng. 22 - 24 tiiang 1,1997, Hd Npi.
2. Dudng Hdng Ddt, 2003. So tay hudng dan si dung phin bdn. NXB Ndng nghilp.
3. Pham Minh Tdm, 2001. Nghiin cuu anh hudng cua viic bdn phan cd dam din ning suit va su biin ddng ham lugng nitiat tiong cai be xanh va tiong dit Ludn vdn thac sy khoa hpc ndng nghilp.
Tnrdng Dai hpc Ndng Ldm Thanh phd Hd Chi Minh.
4. Bd Ndng nghiip vi Phit triin ndng thdn, 2006. Mtic gidi han tdi da cho phep ciia ham lupng nitrat (NO3) trong mdt sd san phdm rau tuoi
(mg/kg). Website, www.moitruong.com.vn 27/02/2010.
5. Biii Quang Xuan, Biii Dinh Dinh, Mai Phuong Anh, 1996. Quan lyhim lugng nitiat tiong rau bing con dudng bdn phin can ddi Bdo cdo tai Hpi thao
"Rau sach", Ha Npi 17 -18/06/1996.
EFFECTS OF NITROGEN RATE AND APPUCATION TIME ON YIELD AND NITRATE CONTENT IN MUSTARD AND LETTUCE OFTHUATHIEN - HUE PROVINCE
Hoang Thi Thai Hoa, Nguyen Do Summary
Experiments were conducted in 2009 - 2010 at Huong Tra district, Thua Thien - Hue province including two factors as N rates (0, 30, 60, 90 and 120 kg N/ha) and two application times (before harvesting 15 and 7 days). Results of experiments indicate that N rates and application times had effects on some growth parameters of mustard and lettuce such as duration, plant height leaf number and canopy diameter. In general, these parameters had the highest values with application rates of 90 kg N/ha and 120 kg N/ha.
Yields of mustard and lettuce were the highest at application of 120 kg N/ha and 90 kg N/ha, respectively.
NO3 contents in mustard and lettuce increased with increasing N rates. NO3 contents were the highest at 120 kg N/ha and over accepted standard level when N was applied before harvesting 7 days. NO3- contents in vegetables at before harvesting 15 days were lower than before harvesting 7 days at different N rates.
Key words: Application times, Nrates, nitrate content, vegetable, yield.
Ngudi phan bi|n: TS. Biii Huy Hiln
