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J, Agronomy & Crop Science 162, 305—309 (1989) © 1989 Paul Parey Scientific Publishers, Berlin and Hamburg ISSN 0931-2250 University of Perademya, Department of Crop Science, Faculty of Agriculture, Peradeniya, Sri Lanka Effect of Method of Inoculation and Nitrogen Fertilizer on Nodulation and Yield of Selected Tropical Legumes U. R. SANGAKKARA and B. MARAMBE Authors' address: Dr. U. R. SANGAKKARA and Mr. B. MARAMBE, Faculty of Agriculture, University of Peradeniya, Peradeniya, Sri Lanka. With 2 tables Received September 12, 1988; accepted December 6, 1988 Abstract Many factors affect nodulation of legumes of which, nitrogen fertilizer and method of inoculation play a vital role. Thus, a study evaluated the effects of the above factors on nodulation and yields of two common tropical food legumes, namely Mungbean and Bushbeans which are considered extensive and poor nodulating species respectively. Inoculation increased nodutation of bushbeans and to a lesser extent in mungbeans. This effect was more evident with time. Nodulation was reduced m the presence of nitrogen fertilizer, and the effect was more pronounced in the extensively nodulating species, mungbean. Nitrogen and nodulation increased yields of both species. The results indicate the mabihty of bushbeans and to a lesser extent mungbean, to meet all nitrogen requirements by nodulation and nitrogen fixation alone. This suggests the need for some fertilizer nitrogen for tropical legumes in addition to inoculation to obtain optimal yields. Introduction Most tropical legumes show free nodulation without inoculation when compared to tem- perate species. However, DOBREINER (1977) showed that some indiscriminate legumes re- quire specific strains of rhizobia for inocula- tion. In addition, native rhizobia populations specific for legumes differ in effectiveness in symbiosis. The effectiveness of inoculum varies with the method of inoculation (BROCKWELL 1982). The response to inoculation also differs with the legume species. Studies on soybeans (WIL- SON 1975) show that nitrogen fixation is re- duced when inoculum is placed in deep soil. HALLIDAY (1979) reports the direct response of nodulation of Siratro to lime pelleting in con- trast to Stylosanthes. MENGEL and KIRKBY (1982) report that nitro- gen has a negative impact on nodule formation. However, the sensitivity of inoculum and rhizobium to nitrogen varies with the crop. Thus, soybean is considered more susceptible to nitrogen that lentils in terms of nodulation and nitrogen fixation (SANGAKKARA and CHO 1987). CHESNEY (1975) also reports the reduc- tion in nodulation of groundnut due to high rates of nitrogen fertilizer. There is a paucity of information on the response of tropical legumes to methods of inoculation carried out together with nitrogen fertilizer. Hence, an experiment was con- ducted and repeated to study the impact of inoculation methods and nitrogen fertilizer on nodulation of two common tropical legumes, namely Bushbeans {Phaseolus vulgaris) and U.S, Copyright Clearance Center Code Statement: 0931-2250/89/6205-0305$02.50/0

Effect of Method of Inoculation and Nitrogen Fertilizer on Nodulation and Yield of Selected Tropical Legumes

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J, Agronomy & Crop Science 162, 305—309 (1989)

© 1989 Paul Parey Scientific Publishers, Berlin and HamburgISSN 0931-2250

University of Perademya, Department of Crop Science, Faculty of Agriculture,Peradeniya, Sri Lanka

Effect of Method of Inoculation and Nitrogen Fertilizeron Nodulation and Yield of Selected Tropical Legumes

U. R. SANGAKKARA and B. MARAMBE

Authors' address: Dr. U. R. SANGAKKARA and Mr. B. MARAMBE, Faculty of Agriculture, University ofPeradeniya, Peradeniya, Sri Lanka.

With 2 tables

Received September 12, 1988; accepted December 6, 1988

Abstract

Many factors affect nodulation of legumes of which, nitrogen fertilizer and method of inoculation play a vitalrole. Thus, a study evaluated the effects of the above factors on nodulation and yields of two common tropicalfood legumes, namely Mungbean and Bushbeans which are considered extensive and poor nodulating speciesrespectively.

Inoculation increased nodutation of bushbeans and to a lesser extent in mungbeans. This effect was moreevident with time. Nodulation was reduced m the presence of nitrogen fertilizer, and the effect was morepronounced in the extensively nodulating species, mungbean. Nitrogen and nodulation increased yields ofboth species. The results indicate the mabihty of bushbeans and to a lesser extent mungbean, to meet allnitrogen requirements by nodulation and nitrogen fixation alone. This suggests the need for some fertilizernitrogen for tropical legumes in addition to inoculation to obtain optimal yields.

Introduction

Most tropical legumes show free nodulationwithout inoculation when compared to tem-perate species. However, DOBREINER (1977)showed that some indiscriminate legumes re-quire specific strains of rhizobia for inocula-tion. In addition, native rhizobia populationsspecific for legumes differ in effectiveness insymbiosis.

The effectiveness of inoculum varies withthe method of inoculation (BROCKWELL 1982).The response to inoculation also differs withthe legume species. Studies on soybeans (WIL-SON 1975) show that nitrogen fixation is re-duced when inoculum is placed in deep soil.HALLIDAY (1979) reports the direct response ofnodulation of Siratro to lime pelleting in con-trast to Stylosanthes.

MENGEL and KIRKBY (1982) report that nitro-gen has a negative impact on nodule formation.However, the sensitivity of inoculum andrhizobium to nitrogen varies with the crop.Thus, soybean is considered more susceptibleto nitrogen that lentils in terms of nodulationand nitrogen fixation (SANGAKKARA and CHO

1987). CHESNEY (1975) also reports the reduc-tion in nodulation of groundnut due to highrates of nitrogen fertilizer.

There is a paucity of information on theresponse of tropical legumes to methods ofinoculation carried out together with nitrogenfertilizer. Hence, an experiment was con-ducted and repeated to study the impact ofinoculation methods and nitrogen fertilizer onnodulation of two common tropical legumes,namely Bushbeans {Phaseolus vulgaris) and

U.S, Copyright Clearance Center Code Statement: 0931-2250/89/6205-0305$02.50/0

306 SANGAKKARA and MARAMBE

Mungbean {Vigna radiata)^ which are consid-ered poor and extensive nodulating species re-spectively.

Materials and Methods

Experiments were conducted on two occasions at theFaculty of Agriculture, University of Peradeniya(7°N, 80°E, 480 Masl). The environmental condi-tions during the trials were — mean temperature26—31 °C, relative humidity 76.9 % ± 4.2 %, witha 9—10 hour daylength.

The selected species, bushbeans (a poor nodulator)and mungbean (promiscuous nodulator) were grownin 25 X 20 mm tubular polythene bags containing2.5 kg of a potting mixture made up of 1 : 1 ratio oftop soil and sand. The total nitrogen content of themedium was 0.14%, with a pH of 6.3 ± 0.14.Approximately four seeds were sown per bag andthinned to one plant per bag after germination.

Two single stram host specific rhizobium ln-oculae, namely TAL 1383 (Bushbean) and TAL 441(mungbean) were applied in four different methods.These were — seed addition prior to plantmg, and tosoil at planting, two days prior to planting and aftergermination. The peat filtered lnoculants were ap-plied at a rate of 35 g per 350 g of bushbeans and440 g of mungbean seeds.

Ail soil applications were incorporated with soil toa depth of 3 cm. The inoculation treatments weremade with or without nitrogen fertilizer at plantingusing urea (46 % N) as the nitrogen source. Aninoculated control with fertilizer nitrogen was main-tained for comparison.

All plants were supplied with a uniform basalfertilizer rate of 21 : 14 P1O5 : K^O, applied at a rateof 250 kg/ha. The nitrogen levels for bushbeans andmungbeans were 250 and 25 kg • N per ha respec-tively.

Ail treatments were replicated three times on twooccasions using a completeiy randomized design.

The number of nodules per plant was determinedby washing the root systems at 21 days after plantingand at flowering. The effectiveness of nodules wasacertained by examining their colour. The yield pa-rameters determined in bushbeans were number ofpods and yield per plant. In nnungbean, the numberof pods per plant, number of seeds per pod, 100 seedweight and seed weight per plant (yield) were deter-mined. Due to similarities of results of both trials thedata was pooled for analysis of variance.

Results and Discussion

Bushheans

Inoculation increased nodulation (Table 1).The response was most significant when seedswere inoculated. Nodulation was reducedwhen inoculum was added to the soil whencompared with seed inoculation. The resultsshowed non significant differences betweenmethods of soil inoculation. However, therewas a marginal increase of nodule numberswhen the inoculum was added to the soil atplanting, rather than earlier or later. The ab-sence of nodules in the uninoculated controlclearly illustrates the poor nodulation charac-teristics of bushbeans.

Table 1. Effect of method of inocuiation and nitrogen fixation on nodulation and yields of Bushbeans

Treatments

Method of inoculation

Nodules/plant

Nitrot;en 21DAP

'l'leld/plantAt n J / 1 Yieid/piant

,, . Pods/piant ^ \tlowering (g)

No inoculation

Seed addition

To soil at planting

To soil before planting

To soil after germination

LSD (P = 0.05)

cv%

With N 16.8 133.5

NoNWith N

NoNWith N

No NWithN

NoNWithN

2.60.6

0.80.5

0.8—

1.31.1

0.968.1

8.74.6

3.53.6

2.72.4

3.02.2

2.8921.3

8.921.6

8.519.6

7.016.5

7.314.8

1.75

8.6

84.0184.6

86.7

178.5

81.8

157.8

84.4

130.6

11.25

10.7

Effect of Method of Inoculation and Nitrogen Fertilizer on Nodulation 307

All inoculated treatments without nitrogenfertilizer showed better nodulation at the firstharvest. This indicates that nitrogen has anadverse impact on nodulation of bushbeans.The reduction in nodule numbers was mostprominent when seeds were inoculated.

All nodules seen on the plant at both sam-plings were effective. As the nodule numberswere greater at the second sampling, the resultssuggest greater rhizobial activity in Phaseolusin terms of effective nodule numbers per plantat the time of flowering, confirming earlierreports by CHESNEY (1975).

Inoculation increased yields per plant ofbushbeans, when carried out in combinationwith nitrogen fertilizer. A comparison ofmethods of moculation indicate greater yieldswhen seeds were inoculated in comparisonwith other treatments. If the inoculum is addedto the soil, application at planting or earlierproduces a higher yield than if applied afterplanting. This can be attributed to the need of atime period for the stabilization of the in-oculum in the soil prior to root infection(BROCKWELL 1982).

The absence of nitrogen fertilizer reducesyields significantly although plants are inocu-lated. The yields of inoculated plants with nonitrogen are less than that of the control,where only nitrogen is applied. This indicatesthat bushbeans require fertilizer nitrogen and

inoculation, as the rhizobia or fertilizer alonedo not seem to be effective in meeting the totalnitrogen requirement of this species.

Mungbean

The effects of inoculation treatments and ni-trogen fertilizer on nodulation and yields ofmungbean are presented in Table 2. Nodula-tion of mungbean increases with time, irre-spective of the method of inoculation. Thisagain suggests that effective nodulation re-quires time as suggested by BROCKWELL (1982).

Inoculation increases the number of nodulessignificantly, irrespective of the method of in-oculation. This effect is primarily seen in thefirst sampling due to the availability of theready source of inoculum. In contrast, thenumber of nodules in the control treatment,where no inoculation was carried out, is gre-ater than some inoculated and fertilized treat-ments at the second sampling. This implies theexistance of rhizobium in the soil which infectsmungbean effectively, However, the infectionprocess is slower than when inoculum is add-ed. When comparing methods of inoculation,the data shows the advantage of inoculating theseed when compared to soil addition. If in-oculum is added to soil, incorporation at orprior to planting produces greater numbers ofnodules in mungbean, primarily due to theavailability of time for stabilization.

Table 2. Effect of method of inoculation and nitrogen fertilizer on nodulation and yields of Mungbeans

Treatments

Method of inoculation

No inoculation

Seed addition

To soil at planting

To soil before planting

To soil after germination

LSD (P = 0.05)

cv%

Nodules/plant

Nitrogen

With N

NoNWithN

NoNWith N

NoNWithN

NoNWithN

21DAP

10.4

16.312.3

12.012.6

13.010.6

10.312.6

1.9314.4

Atflowering

21.1

29.320.3

22.319.6

24.818.0

20.719.7

3.748.97

Yield parameters

Pods/pL Seeds/pod

16.9

17.718.8

17.318.6

17.016.6

16.318.2

1.184.2

S.2

8.68.6

8.48.0

8.38.0

8.28.5

NS2.3

100 Seedwt (g)

3.45

3.59

3.62

3.493.64

3.483.54

3.463.54

NS8.5

Yield/pl.

(g)

S.3

6.510.1

6.19.1

5.7

9.6

5.2S.I

0.5214.49

22 =>

308 SANGAKKARA and MARAMBE

The effect of fertilizer nitrogen on nodula-tion is not significant at the first sampling,although a trend of reduction is observed.However, nitrogen significantly reducesnodules at flowering. This as reported by NOR-RIS and DATE (1976) illustrates the adverse ef-fects of nitrogen on nodulation in readilynodulating species with of without inocula-tion. The reduction in nodulation may be dueto the ready source of nitrogen in the soil,which makes the nodules ineffective in fixingatmospheric nitrogen.

The yields and some yield components ofmungbean are affected by the adopted treat-ments (Table 2). The number of seeds per podand 100 seed weight which are indicators ofeffective translocation of photosynthates(MENGEL and KIRKBY 1982) are not affected bythe adopted treatments. However, the numberof pods per plant are affected by the inocula-tion and nitrogen treatments. Thus, yield dif-ferences are observed between treatments.

Yields of mungbean are highest when seedinoculation is carried out along with nitrogenfertilizer. If inoculum is added to the soil, thehighest yields are seen when inoculation iscarried out at planting. A comparison of thecontrol treatment and treatments where inocu-lation is carried out without nitrogen showbetter yielding ability of the former. This sug-gests the importance of nitrogen fertilizer inobtaining higher yields in this readily nodulat-ing species. The need for inoculation as well asnitrogen fertiHzer indicates the inability of thenodules to effectively meet the nitrogen re-quirements of mungbean, a readily nodulatingspecies, under the adopted experimental condi-tions. This can be attributed to the imbalancethat exists between nodule numbers and nitro-gen fixation in legumes growing in the tropics.

General Discussion

This study evaluated the response of a poorand readily nodulating legume species to in-oculation methods and nitrogen fertilizer.Bushbeans, if not inoculated but fertilized withnitrogen, reduces yields by 38 %, in compari-son to the best yield obtained by inoculation.In contrast, the reduction m yield in mung-beans in the similar treatments is 21 %. Thisindicates the ability of mungbean, a readilynodulating species to meet a major proportion

of its nitrogen requirements in contrast to thepoor nodulating species, bushbeans. However,both species are not able to produce optimalyields by inoculation or by nitrogen fertilizeralone, thus illustrating the need for both treat-ments due to the inherent inability of the plantto meet total nitrogen requirements by nodula-tion alone.

A comparison of methods of inoculation ofboth species indicate the value of seed inocula-tion in contrast to soil incorporation. The val-ue of seed inoculation occurs from the abilityof the rhizobium to be at the site of rootdevelopment. If added to soil, incorporation atplanting produces better yields. Thus, in tropi-cal legume culture, addition of inoculum toseed and addition of some nitrogen fertilizerseem to be vital for high yields.

Zusammenfassung

Einflufi der Inokulationsmethode und desStickstoffdiingers auf die Knollchenbildungund den Ertrag verschiedener tropischerLeguminosen

Viele Faktoren beeinflussen die Knollchenbil-dung von Leguminosen; insbesondere Stick-stoffdiinger und das Verfahren der Inokulationspielen eine wesentliche Rolle. Es wurden da-her in einem Versuch die genannten Faktorenhinsichtlich der Knollchenbildung und der Er-trage von zwei tropischen Nahrungslegumino-sen — Mungbohne und Buschbohne — unter-sucht; diese Arten sollen eine starke bzw.schwache Knollchenbildung aufweisen*. DieInokulation erhohte die Knollchenbildung vonBuschbohnen und, in einem geringercn Um-fang, auch von Mungbohnen. Diese Wirkungwurde mit zunehmender Zeit deutlicher. DieKnollchenbildung wurde in Gegenwart vonStickstoffdiinger reduziert, wobei die Wirkungbei der stark knollchenbildenden Art Mung-bohne starker ausgepragt war. Stickstoff undKnollchenbildung erhohten den Ertrag beiderArten. Die Ergebnisse lassen vermuten, dafibei Buschbohnen und in einem geringerenUmfang bei Mungbohnen nicht der gesamteStickstoffbedarf durch die Knollchenbildungund die Stickstoffixierung abgedeckt werdenkann. Dies weist darauf hin, dafi fiir Hochster-trage eine gewisse Stickstoffdungung nebcn derInokulation notwendig ist.

Effect of Method of InocuLition and Nitrogen Fertilizer on Nodulation 309

Acknowledgements

The Sri Lanka—Belgiutn Biological N Fixation pro-ject at the Faculty of Agriculture is thanked forprovision of the inoculunn. Gratitude is expressed tothe University of Peradeniya for the award of aresearch grant RG/14/C86/AG.

References

BROCKWELL, J., 1982: Inoculation methods for fieldexperimentation and farmers. In: ViNCENT, J. M.(ed.), N Fixation of legumes, pp.211—219.Academic Press, Australia.

CHESNEY, Fi. A. D., 1975: Fertilizer studies withgroundnut on the brown sands of Guayana. I.Effects of Nitrogen, inoculum, Magnesium andfritted nutrients. Agronomy Journal 67, 7—10.

DOBREINER, J., 1977; Present and future oppor-tunities to improve the nitrogen nutrition of cropsthrough biological N fixation. In: Bio-logical N

fixation in the farming systems of the tropics,pp. 3—12. IITA, Nigeria.

HALLIDAY, J. , 1979: Pasture production in acid soilsof the tropics. SANCHEZ, P. A., and L. E. TERGAS

(eds.). CIAT, Gah, Colombia, pp. 123—125.MENGEL, K. , and E. A. KiRKBY, 1982: Principles of

plant nutrition. International Potash Institute,Bern, Switzerland, pp. 336—340.

NORRIS, D. O., and R. A. DATE, 1976: Legumebacteriology. In: SHAW, N . H . , and \V. BRYAN

(eds.), Tropical pasture research, pp. 134—174.Commonwealth Agric. Bureaux Bulletin 51, U.K.

SANGAKKARy\, U. R., and G. M. C H O , 1987: Rela-tionship between fertilizer N and N fixation inlentils and soybeans. In: WALLIS, E. S., and D. E.B\TIIE (eds,), Food legume improvement for AsianFarming systems, pp. 2S0—281. AGIAR Proceed-ings 18, ACIAR, Australia.

WILSON, D . O . , 1975: Nitrogen fixation by soy-beans as influenced by inoculum placement. Ag-ronomy Journal 67, 76—78.