Pr odu ct ion a n d Ph y siologica l Ch a r a ct e r s of Soy be a n
Va r ie t ie s U n de r D r ou g h t St r e ss w it h Applica t ion of
N it r oge n Sou r ce s
1
Yaya Hasanah,
1*Tengku Chairun Nisa,
2Hapsoh, and
1Ham idah Hanum
1
Facult y of Agricult ure, Universit y of Sum at era Ut ara, Medan 20155, I ndonesia;
2Facult y of Agricult ure, Universit y of Riau, Pekanbaru 29293, I ndonesia.
* Corresponding Aut hor
: azkia_khairunnisa@yahoo.co.id
Abst r a ct
Soy bean is a legum e sensit iv e t o drought condit ions result ing in decreased y ield and seed qualit y . Dr ought st ress on plant s also in hibit s nit rogen upt ak e. The obj ect iv e of t he research w as t o det erm ine product ion and phy siological charact ers of soy bean v ariet ies under drought st ress t hrough nut rient N m anagem en t . This resear ch used a random ized block design w it h 3 fact ors and 3 replicat ions. The first fact or w as soy bean v ariet ies ( Anj asm or o, Wilis and Sinabung) . The second fact or w as drought st ress condit ions consist ed of 50% , 60% , 70% and 80% of field capacit y ( FC) . The t hird fact or w as t he applicat ion of N consist ed of ( 1) . Wit hou t applicat ion of N fert ilizer ( cont r ol) ; ( 2) . N fert ilizer dose of recom m endat ion ( 50 k g Urea/ ha) ; ( 3) . I noculat ion of Brady rhizobiu m sp. ; ( 4) . Organ ic N sou rces ( st r aw com post 10 t ons/ ha) ; ( 5) . Organic N sources ( farm y ard m anure 10 t ons/ ha) . The result s suggest t hat Anj asm or o v ariet y im prov ed dry w eight of seed per plant com pared w it h Willis and Sinabung. I n creased drought st ress ( 80- 50 % of FC) result ed in a decrease in dr y w eight of seed per plant . Sources of N in t he form of urea or Brady rhizobiu m sp. increased t he dry w eight of seeds per plan t com pared w it h t reat m ent N sources st raw and m anure com post . The int eract ion bet w een Brady rhizobium sp. or Urea and Anj asm oro v ariet y im prov ed dry w eight of seeds per plant .
Ke yw o r ds : drought st ress, nit rogen, product ion, phy siological charact er, soy bean
I n t r od u ct ion
Soybean (Glycine m ax ( L.) is t he m ost im port ant legum crop of t he world and a m ajor source of protein, energy, polyunsat urat ed fat , fibres bot h for hum ans and livestock. I n addit ion t o being a source of m acronut rient s and m inerals, soybeans cont ain secondary m et abolit es such as isoflavones ( Sakai and Kogiso, 2008) , saponins, phyt ic acid, oligosaccharides, goit rogens ( Liener 1994) and phyt oest rogens ( Ososki and Kennelly, 2003) . Yield in soybean is highly affected by drought st ress, part icularly when the st ress occurring during flowering and early pod expansion ( Liu, 2004 ; Liu et al., 2004 ; Purcell et al, 2004), short ens plant , suppressing t he developm ent of soybean root and shoot ( Ham im et al., 1996; Soepandi et al., 1997) , accelerate flowering and harvest age ( Jusuf et al.,
( 1993) , reducing the num ber of filled pods ( Soepandi et al., ( 1997) , lowering the num ber of seeds/ plant and seed weight per unit ( de Souza et al., 1997) and lower seed yield of soybean ( Jusuf
et al., 1993; Soepandi et al., 1997). Drought st ress on plants also inhibits nit rogen, phosphorus and potassium uptake in plant s. Generally, drought reduces both nut rient upt ake by t he roots and t ransport from t he roots t o t he shoots, because of rest rict ed t ranspirat ion rates and im paired act ive t ransport and m em brane perm eabilit y ( Tanguilig et al., 1987 ; Hu and Schm idhalt er, 2005) .
Nit rogen is t he m ineral elem ent t hat plants require in t he largest am ount s and a const ituent of m any plant cell com ponents, including am ino and nucleic acids ( Hu and Schm idhalter, 2005). I t required in t he synt hesis of chlorophyll, and also the form at ion and growt h of the vegetat ive parts of t he plant .
organic fert ilizer N per area. I n addit ion, t he use of organic N fert ilizer for crops is necessary t o ensure that the organic N fert ilizer m aterials have decom posed well, because oft en t im es t he use of organic N will have no effect on t he plant as a source of organic N is not decom pose properly ( Hartat ik and Widowat i, 2006) . I n addit ion, t he use of bio- fertilizers on dry land is indispensable for biological fert ilit y in dryland soybean crop is generally low and is one t ype of legum e t hat is act ive in t ie up N from t he air, so t hat the inoculat ion of Bradyrhizobium sp. is an effort to reduce dependence on chem ical fert ilizers (Prihast ut i, 2012) .
An early study of t he relat ionships bet ween wat er availabilit y and t he N- fert ilizer responses from Bloem et al. ( 1992) dem onst ated t hat applicat ion of addit ional N enhanced wheat yield only when t he drought was not severe. While drought condit ions m ay reduce soil- N m ineralizat ion, t hus lowering t he N availabilit y. Tanguilig et al. ( 1987) also dem onst rat ed t hat a reduced crop N uptake m ay also be at t ribut ed t o a decreased t ranspirat ion rate t o t ransport N from root s t o shoot s. Based on t he background, t his research was conduct ed t o determ ine t he product ion and physiological charact ers of soybean variet ies under drought st ress t hrough nut rient N m anagem ent .
M a t e r ia ls a nd M e t h ods
Se t up of th e e xp e r im e n t
The research was conducted at t he screen house Facult y of Agricult ure, Universit y of Sum at era Utara, Medan, I ndonesia on February t o May 2012. Soil for t he research was t aken from dry land Sam birej o Village ( Dist rict of Binjei, Langkat ) .
Ex p er im e n t al de sign a nd crop m a n ag e m en t
This research used a random ized block design wit h 3 fact ors and 3 replicat ions. The first fact or was soybean variet ies ( Anjasm oro, Wilis and Sinabung). The second fact or was drought st ress condit ions consist ing of 50% , 60% , 70% and 80% of field capacit y ( FC) . Drought st ress t reat m ent of 80% of FC is t he cont rol t reatm ent because it was considered opt im al for the growt h of soybean (Chen et al., 2006; Sum arno and Mansuri, 2007). The t hird fact or was t he applicat ion of N consist s of ( 1) . Wit hout N fert ilizer (cont rol) ; ( 2) . N fert ilizer dose of recom m endat ion ( 50 kg Urea/ ha) ; ( 3) . I noculat ion of
Bradyrhizobium sp.) ; ( 4) . Organic N sources ( st raw com post 10 t ons/ ha) ; ( 5) . Organic N sources ( farm yard m anure 10 t ons/ ha) . There were 3 x 4 x 5 x 3 = 180 experim ental unit s. Each experim ent al unit consisted of 4 plants so t here were 540 polybags.
Three soybean variet ies ( Anj asm oro, Wilis and Sinabung) was used as source of seeds. The soil dried for 15 days, t hen crushed and screened with a diam eter of 6 m m sieve. Before plant ing, soil lim ed wit h dolom it e 500 kg/ ha and incubated for 2 weeks. A t ot al of 10 kg weight of air- dry soil put in poly bag size 30 cm x 40 cm . Poly bag had previously been covered wit h plast ic. I solates of
Bradyrhizobium sp. indigenous origin dry land village Sam birejo obtained by isolated first . Based on t he pre- st udy results t he isolat es of Bradyrhizobium sp. pot ent ial. Propagat ion of Bradyrhizobium sp. isolate conduct ed in Soil Biology Laborat ory, Facult y of Agricult ure, Universit y of Sum atera Ut ara by using yeast ext ract m annit ol m edium in a 500 m l flask were shaken 150 rpm at room tem perature for 48 hours. B. j aponicum inoculat ion were m ixed wit h soybean seed j ust before plant ing in t he shade in t he m orning. Bact erial isolat es ( densit y of 108 cells/ m l) in 1 m l/ poly bag was also given t o t he ground in a poly bag. St raw com post m ade wit h bio-act ivat or Trichoderm a harzianum.
The t ransparent plast ic shade was m ade inside t he screen house wit h a size of 12 m x 16 m m ade of bam boo and wire bonded. I t was divided int o 3 blocks. Determ inat ion of soil m oisture cont ent t o det erm ine t he weight of air- dry soil t o be put int o polybag done by drying m ethod. Determ inat ion of water content at field capacit y (FC) was conducted using m et hod describe by Alt ricks ( Fot h, 2004). P and K fert ilizer applicat ion was done for all t he plant s at plant ing t im e ( 0 days after plant ing/ DAP) according to t he dose of 150 kg TSP/ ha and 75 kg KCl/ ha. Urea 50 kg/ ha applied at t wice i.e. a half of dose on plant ing t im e ( 0 DAP) and a half of dose on 30 DAP. Cow m anure and st raw com post ing was done at plant ing t im e according t o t reat m ent, adm inist ered by m ixing fert ilizer wit h plant ing m edium .
carried out by using organic pest icides. Harvest ing is done if t he soybean crop has shown t hat t he crit eria have brown skin pods and stem s and leaves have dried up variables observat ions.
Variables observed and stat ist ical dat a analysis
Variables observed was chlorophyll, shoot and root N content and seed dry weight per plant . Chlorophyll content m easured by using Opt i- Sciences CCM 200 plus Chlorophyl m eters (Opt i- Sciences, 2011) . Shoot and root N m easured by Kj edhal m ethod. I f t here were significant differences in the variance analysis followed by Duncan's Mult iple Range Test ( p = 0.05) .
Resu lts a nd D iscussion
Soil, Far m y a rd m a nu r e an d St r a w Com p ost Ch a ra ct e r ist ics
The charact erist ics of soil had low pH H2O 5.0, low of N cont ent ( 0.14% ) , low C organic content ( 1.02% ), sufficient P ( 27.4 m g kg- 1) , sufficient K (0.47 m e/ 100) , sufficient Ca (8.75 m e/ 100), low cat ion exchange capacit y ( 15.7 cm ol( + ) kg- 1, high Mg ( 3.69 m e/ 100). The st raw com post characterist ic were C organic content 22.5 % , N t otal 1.33% , C/ N rat io 16.9, P2O5 t otal 2.9% , K2O 9.45. The characterist ics of farm yard m anure had t he C organic content 17.98 % , N t otal 1.04% , C/ N rat io 17.28, P2O5 t otal 0.79% , K2O 0.30.
Ph ysiolog ica l ch a r a ct e rs of soyb e an Ch lor op hy ll Con t e n t
Anj asm oro and Sinabung variet ies gave t he highest of chlorophyll cont ent com pared t o Wilis. Applicat ion of Urea tent t o increase t he chlorophyll cont ent com pared t o ot her t reat m ent s. I nt eract ion bet ween Anjasm oro variet y and 60% of FC gave t he highest of chlorophyll cont ent , but int eract ion bet ween Sinabung variet y and 70% of FC t he lowest of chlorophyll content ( Table 1) .
Sh oot N con t e n t
Anj asm oro variet y provide t he highest shoot N content com pared t o Sinabung and Wilis. Farm yard m anure t reatm ent im proved shoot N content significant ly t han other t reatm ent s, but t he t reat m ent of wit hout N gave the lowest shoot N cont ent . Drought st ress t reatm ent did not give effect significant ly different on shoot N content ( Table 2) .
Root N con t en t
Urea t reat m ent im proved t he root N cont ent significant ly com pared t o ot her t reat m ent s. Manure t reat m ent gave the lowest root N content. I nteract ion Anj asm oro variet y wit h st raw com post produced t he highest levels of N roots t han ot her t reatm ents, but not significant ly different from t he interact ion of Anj asm oro variet y and aplicat ion of Urea. The interact ion between Urea and 70% of FC produced t he highest levels of N roots ( Table 3) .
Table 1. Chlorophyll cont ent of t hree soybeans variet ies under drought st ress wit h applicat ion of source of N
Treatm ent Drought st ress ( % of FC) Mean
50 60 70 80
Variet y ………unit / 0.71 cm2 ………..
Anj asm oro 33.14 35.48 31.70 34.03 33.53a
Sinabung 31.22 28.12 27.33 29.38 35.53a
Wilis 27.37 28.98 28.83 28.00 29.01b
Source of N
Wit hout N 29.89 31.57 29.20 28.72 29.85
Urea 30.58 30.75 31.49 31.66 31.12
Bradyrhizobium sp. 30.62 29.80 30.50 29.95 30.22
Farm yard m anure 30.31 30.72 29.27 30.64 30.23
St raw com post 31.46 31.46 25.96 31.39 30.07
Mean 30.57 30.86 29.28 30.47
Table 2. Shoot N content of t hree soybeans variet ies under drought st ress with applicat ion of source of N
Drought st ress ( % of FC) Mean
50 60 70 80
Variet y ………% of shoot dry weight ………..
Anj asm oro 3.86 3.89 4.02 3.68 3.86x
Sinabung 3.43 3.48 3.61 3.40 3.48z
Wilis 3.94 3.71 3.52 3.26 3.61y
Source of N
Wit hout N 3.51 3.51 3.49 3.29 3.45d
Urea 3.72 3.79 3.63 3.47 3.65c
Bradyrhizobium sp. 3.57 3.14 3.36 3.57 3.41d
Farm yard m anure 3.83 4.17 4.22 3.65 3.97a
St raw com post 4.10 3.85 3.89 3.26 3.77b
Mean 3.75 3.69 3.72 3.45
Not e : Different let ters at t he sam e group t reat m ent represent significant differences at Duncan’s Mult iple Range Test (p = 0.05)
Table 3. Root N content of t hree soybeans variet ies under drought st ress wit h applicat ion of source of N
Drought st ress ( % of FC) Mean
50 60 70 80
Variet y ………% of root dry weight ………
Anj asm oro 2.20 2.24 2.35 2.16 2.24x
Sinabung 1.92 2.05 1.91 1.83 1.93y
Wilis 1.79 1.94 1.93 2.06 1.93y
Source of N
Wit hout N 1.96cde 1.99cde 2.08abcd 1.96cde 2.00l
Urea 1.99cde 2.34ab 2.36a 2.03cde 2.18j
Bradyrhizobium sp. 2.20abc 2.05bcde 1.81e 2.13abcd 2.05k Farm yard m anure 1.89de 1.95cde 1.78e 1.92cde 1.88m St raw com post 1.82e 2.05bcde 2.29abc 2.03cde 2.05k
Mean 1.97 2.08 2.06 2.01
Not e : Different let ters at t he sam e group t reat m ent represent significant differences at Duncan’s Mult iple Range Test (p = 0.05)
The applicat ion of Urea gave t he highest root N cont ent, while applicat ion of farm yard m anure gave t he lowest root N cont ent . I nteract ion bet ween Anj asm oro and applicat ion of st raw com post gave t he highest root N content, while the int eract ion bet ween Sinabung variet y and Bradyrhizobium sp. provide t he lowest of root of N ( Table 4).
Table 4. Root N cont ent of t hree soybean variet ies wit h t he applicat ion of N sources
Variet y Source of N
Mean Wit hout N Urea Bradyrhizobium
sp.
Farm yard m anure
St raw com post
...% ...
Anj asm oro 2.13de 2.36ab 2.27bc 2.01f 2.41a 2.24x
Sinabung 2.05ef 2.01f 1.81h 1.91g 1.86h 1.93y
Wilis 1.82h 2.18cd 2.06ef 1.73i 1.87h 1.93y
Mean 2.001 2.18j 2.05k 1.88m 2.05k
Pr od u ct ion of soyb e a n Se e d dr y w e ig h t p e r pla n t
Based on Table 9 shown t hat Anjasm oro variet y produced t he highest dry seed weight per plant com pared wit h Sinabung and Wilis. Treatm ent of 70-80% of FC increased the dry weight of seeds per plant significant ly com pared with 50% and 60% of FC. I n all variet ies is seen t hat the dry seed weight per plant tent to increase wit h increasing% KL.
Table 5. Seed dry weight of t hree soybean variet ies under drought st ress wit h t he applicat ion of N sources
Drought st ress ( % of FC) Mean
50 60 70 80
Variet y ……… g ………..
Anj asm oro 3.84 3.47 4.85 5.51 4.42a
Sinabung 3.49 3.83 4.17 4.78 4.07b
Wilis 2.81 3.44 4.12 4.34 3.68c
Source of N
Wit hout N 3.43 2.67 5.62 5.61 4.33
Urea 3.33 3.70 3.72 3.70 3.61
Bradyrhizobium sp. 2.48 5.25 3.87 4.48 4.02
Farm yard m anure 3.34 3.51 3.85 4.95 3.91
St raw com post 4.87 4.00 3.79 5.16 4.46
Mean 3.49y 3.83y 4.17x 4.78x
Not e : Different let ters at t he sam e group t reat m ent represent significant differences at Duncan’s Mult iple Range Test (p < 0.05)
Based on t he research result s chlorophyll content influenced by variet ies ( Table 1) . Anjasm oro had t he chlorophyll content higher than Willis and Sinabung. Treatm ent of 50 - 80% of FC has not responded significant ly different wit h chlorophyll cntent . Chlorophyll cont ent related t o t he st atus of N in plant indicated by t he shoot N content ( Richardson et al., 2002) . The low chlorophyll cont ent also indicat ed t he low shoot N content. This is evidenced in t his research t hat t reatm ent wit hout N applicat ion produced low chlorophyll cont ent ( Table 1) and also lowest shoot N content ( Table 2) , because t he t reatm ent wit hout N applicat ion led t o a shortage of plant N t hat leaves becom e paler due t o t he loss of chlorophyll which is pigm ent s in photosynt hesis. As already reported by Ashari ( 2006 ) t hat Nit rogen is one of the com ponents of chlorophyll which plays an im port ant role in photosynthesis. N deficiency sym ptom s are m ost obvious and com m only seen is a reduct ion in leaf green color due t o t he loss of chlorophyll, t he green pigm ent t hat plays a role in phot osynt hesis. N is an essent ial elem ent for plant growth which is a protein const it uent of nucleic acids, st im ulat e overall growt h, const it uent prot oplasm , chlorophyll m olecules , nucleic acids and am ino acids which are t he building of protein.
Based on the lim its of nut rient sufficiency and deficiency according t o the result s of the analysis of t he shoot N content , in general it is in a st ate of deficiency because a value less than 4.2 % ( Hardj owigeno, 2003) . I n t his research, t reat m ent of variet ies significant ly affect on shoot and root N content ( Tables 2 and 3). Shoot N cont ent in Anj asm oro higher t han Wilis and Sinabung. This phenom enon is relat ed t o the abilit y of each variet y in absorbing N nut rient s from the soil. There are t wo form s of N fixat ion by plant root s nam ely am m onium and nit rat e. Nit rogen is absorbed m ost ly in t he form of nit rat e ions are st ored direct ly in t he vacuole cells of root , st orage organs ( fruit ) , stem s or leaves . The rest which are not stored in t he vacuole would be reduced to NO2 ( nit rite) converted into am m onia ( NH3) by enzym es nit rit reduct ase.
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