Joamal of Agriculture in the Tropics and Subtropics
'-olume 102, No.2, October 2001, pp. 109 -Il7
Influence of legume fallow on soil properties and yield of
maize in South Western Nigeria
J. A. Adediran, M. O. Akande, V. A. Banjoko, G. A. Oluwatosin and L. B. Taiwo
I
."'bstract
srudy was conducted to investigale the influence of some legwne fallows on the
.' ) ico-chemical properties of so il and grain yield of maize in oUlhwestern Nigeria.
reannenrs consisting of four fallows with Mucuna uti/is, Centrosema brasiliensis,
Canavalia ensiformis and Cajanlls cajan were planted and allowed to fallow for three
The fa llow crops were incorporated into the soil at the end of each of the three
. Maize was planted as indicator crop only al the end of the third year. SoB and
I analyses were done. Maize was harvested at maturity and grain yield calcu lated at
12% moisture content.
_=.
Results showed that the fallow crops with exception of centrosema improved soil
kni lity aod increased soil organic matter from 1.07% at pre-crop 102. 10, 1.90% and
L 6%, respectively on the cajanus, canavalia and mucuua plots after three year of
fallow. The cation exchange capacity and ph osphorus however increased almost three
old in these fallow plots. The fallow crops po itively affecled nutrient concentration in
ear tissue and grain. yje ld of maize. The coefficie nt of correlation (r) fo r N, P and K
ith yie ld was 0.93 , 0.77 and 0.30 respectively. In term of effectiveness the fallow
crop are ra ted in the following ascending order - cajanus, mucuna. canavalia
entrosema and bush. Application ofNPK fertilizer (50 kg N/ha) on the plots IlDder
fallow with natura l bush and centrosema gave re pectively 67 and 79% yield increase
compared with plots without fertilizer. There was indication that, little or no fertilizer
would be required on the other treatment plots depending on targeted yield and soil
test.
Introduction
Any cropland kept IlDder continuous cultivation without appropriate soil management
loses its strength in supporting good and sustainable crop yield. This is due to
deterioration in soil physical, chemical and biological properties (Juo and LAL, 1977).
To worsen the soil conditions, farmers' practices, which involve intensive cropping
cause rapid decline in soil fertility (JONES, 1971, ABDULAHI and LOMBIN, 1978). The
traditional system commonly acceptable to most farmers in restoring soil fertility of
I
Institute Of Agricultural Research And Training, Obafemi Awolowo University,
Moor Plantation, P M B 5029, [badan, Nigeria,
109
croplandis by allowingit to rest(fallow) for a long periodof time. Restorationof soil
fertility under this systemtakes over 10 years of fallow (Acroole and UNerrarrle,
1994). However, long-term fallow could not be sustainedin recent timös due to
populationpressureon land.Also, land tenwe systemcommonlyadoptedin
increased
many farming communitieshinders direct ownership of land put under fallow.
Restorationof soil fenility by fallowing for a long period is thereforenot well suited
for the presentday food requirements.
Shorteningof fallow period,thereforebecomesatfactive to farmersthat are actively
engagedin food production.However,the use of shortenedfallow without appropriate
measureofenhancing soil fertility graduallyimpoverishesthe soil and causespoor
crop yield. Short-termnaturalfallow hasno measurableeffect il regeneratingsoils
exhaustedby cropping(Pmru,1992).Suchfallow is not iong enoughto replacethe
nutrientsremovedby crops.Thereforeplanting of fallow with appropriatelegume
speciescan improve soil fertility throughnitrogenfxation, recycling ofnutrient, which
consequently
increases
the levelof organicmatterin the soil.
Propermanagement
of selectedfallow speciescanalsosuppress
weeds,reduceerosion
and sustainsoil fertility. Despitesomework earliercarriedout by variousresearchers
on maximization of the potential of legumesfor soil fertility enhancement,it is
advantageous
to firrther investigatethe effectivenessofthe crop speciesunder different
soil and agroecologicalenvironmentsand also someother benefitsderivablefrom
usingsuchlegumesasfallow crops.The numerouswork involving somelegumecrop
plants in intercropping,greenmanuring,alley cropping,cover cropping and rotational
croppingwerereportedby somescientists
(KeNc et al.,1990, Orrcso andLAr, 1977,Orrcso andGrunu-aro. 1976and SrNcn,
1e74).
This paper further examinesthe effect of legumesplantedas fallow crops on soil
propertiesandmaizeyield in the humid forestzoneof SouthwesternNigeria.
2
Materials and Methods
The experimentwas conductedat Institute of Agricultural Researchand Training
croppilg researchstationat Moor Plantationat Ibadanin the humid forest zone of
South westernNigeria. The site used for the experimenthad earlier been put to
continuouscultivationfor eightyearsandrecentlycroppedfor four consecutive
years
with maizeandmaizelcassava
crop mixturebeforethe trial was initiated.The soil of
the experimental
sitewasIwo seriesclassifiedasalfisol(Rhodicplinthustalf- USDA).
The soil was ploughedand harrowedonce.Pre-cropsoil sampleswere taken and
analysedin the laboratory.
The fallow cropsplantedwere Mucuna utilis, Centosema brasiliensis,Canavalia
ensiformisand Cajanuscajan.For ttLelnst threecropsspacingwas 1.00mx 0.50mand
for Centrosema,
it was 0.75mx 0.50m.The fallow cropswereplantedat the on-setof
earlyrains.Plotswith naturalbushservedascheckfor the fallow crops.Themajorplot
110
size was 14m x 5m and the fteatments were arranged in strip design and replicated
three times. With the exception of bush fallow, one manual weeding was carried out on
plots with fallow crops before fal1ow establishment. Although there was incidence of
fre outbreak at the end of first year fallow, the crops wele replanted and left to fallow
fifther in subsequentyears. In the third year however, centrosema was replanted and
rogueing of weed was carefully carried out on the canavalia and mucuna plots to
enlance re-establishmentof the fallows.
At the end ofthe first and second year, a subplot of 3m x 5m was eannarked from the
major plot. Plant biomass was worked into the soil and soil samples were taken for
some physico-chemical properties analysis in the laboratory GITA, 1979). After three
years of fallow, plants biomass was agail worked into the soil on the remaining
treatment plot (8m x 5m). Soil sarnples were taken before cropping and analyzed in the
laboratory. Microbial population was estimated on the Huchinsons agar for bacteria
and actinomycetes as modified by Bnlr and Snqrrv (1949), and on potatoe dextrose
agar for fungi (Ben.nrr, H. L.1960). The plot was divided into two sub-plots. The ltrst
consisted of fallow heatment alone and on the second sub-plot application ofNPK 2010-10 at 50 kg Nlha was done 2 weeks after planting of maize. The variety of maize
planted was DMRLSR-Y. Three seeds were sown per hole and later thiruted to one
plant per stand. The planting space was 75cm x 25cm. Herbicide was applied
immediately after planting and was followed by one light weeding few weeks before
tasseling of maize. other cultural operations were carried out as recommended in the
IAR&T package of recommendations for South western zone of Nigeria (IAR&T,
19 9 1 ) .
Maize ear leaf was sampled and analyzed for nutrient content at 4 and 8 weeks after
planting. The leaf samples were digested with 2:1 mixture of HNO3 and HCIOa a:rd
nitrogen was determined on the tecnicon II Autoanalyzer. Ashing of some subsamples
took place in the muffle fumace at 450' C and K, Ca, Mg' Zn were determined on the
Atomic Absorption Spectrophotometer. Phosphorus was determined spectrophotometrically using Ammonium Molybdenum Ascorbic Acid method. Maize was
harvested at maturity and the grain yield was computed at 120%moisture content.
3
Results
3.1 SoilProperties
Table 1 shows some physical and chernical properties ofthe soil at pre-crop, after one
two and three years of fallow. The first year fallow showed no marked changes in soil
texture, pH and organic C over the pre-crop soil analysis results. However, the C E C
increased between two and four folds (Table 1). This could probably be due to burning
incidence that occurred on the trial site, which might have raised the ash level in the
soil. On the other hand, the available phosphorus increasedby 30 ' 67%. At the end of
the second and third year, the soil texture remained loamy sa:rd with some
improvement in pH and organic carbon. In the second year, mucuna and cajanus
increasedthe soil nitrogen status respectively by 47 and76o/" and the phosphorus level
by 126 and l30olorespectively when compared with what was obtained at pre-crop soil
sampling period.
Table 1: Some physical and chemical properties of the soil under the legume fallows
Treatment
Pre-crop
I yearfallow
Bush
Mucuna
Centrosema
Cajanus
Canavalia
LSD at 5%
cv,%
2 yearsfallow
Bush
Mucuna
Centrosema
Cajanus
Canavalia
LSDat5%
cv,%
3 yearsfallow
Bush
Mucuna
Centrosema
Cajanus
Canavalia
L S Da t5 %
CV,Yo
Sand Silt
Yo
%
89
Clay pH
%
5.7
org C Ca
Mg K
CEC N
o/o
<- Cmol/ks -)
s&e
87 7
87 7
8E 6
87 o
E7 7
6.2 2 . 5
10.5 9.3
6
6
6
7
6
22
11.1
6.0
5.8
5.5
s9
5.9
027
11.6
0.85
0 72
085
0.7s
072
0.13
17.5
296
4.20
430
2.90
631
2.95
1 98
20t 0 14
2 80 0.13
2 66 0 t7
1.93 0.t7
4 22 02t
1.98 0.06
12.5 14.2
5 60 0 90
7 32 0.80
7 80 0.70
s.2s 0.80
1117 0.80
4.08 0.14
2t 5 16.2
3.63
5.42
4.42
5.68
5.46
r.7s
15.5
86
85
86
84
85
54
1.2.s
7
8
E
10
8
25
r0.2
7
7
6
6
7
18
8.7
62
60
5.6
6.2
6.2
0.11
13.4
0.E8
097
0.72
1.06
0.98
0.90
15.5
3.65
4.50
4.42
4.15
6.05
1.02
17.6
2.58
2.75
2.62
2.04
3.61
1.24
13.8
0.18
0 t5
0.18
0.18
026
0 09
16.4
6.62
7.66
7.48
6.74
1024
2.27
t6.2
0.90
1.00
0.90
1.20
0.90
0.44
12.5
4.88
7.68
4.42
7.84
7.45
1.26
17.3
E5
85
85
84
84
6.8
102
8
9
7
l0
9
3.4
11.3
7
6.2
6.1
5.9
6.3
6.4
0.05
12.6
0.94
1.08
0.79
1.21.
1.t0
0.10
11.5
3.E5
4.80
4.02
4.92
6.43
138
12.3
2.54
2.75
2.60
2.10
3.84
1 45
16.2
0.20
020
0 19
0.20
0.28
0.09
14.1
6.78 1.10
8.04 1.20
6.82 0.80
8.43 1 30
1 0 . 8 21 . 2 0
2.05 0.08
15.8 12 5
6.40
9.20
5.88
8.94
8 45
1 67
14.2
b
8
6
7
z.o
v.)
P
ms/ke
0.62 1.40 0.90 0.20 2.76 0.6E 3 40
However, after three years of fallow there were marked changesin some soil
properties.The mucuna,naturalbush,cajanusand canavaliaraisedthe soil pH by 0.4,
0.5,0.6 and0.7 units,respectively.
For nitrogen,the increasewasbetween62 and9lo/o
and for phosphorusit was between88 and 170%.The soil organicmatter content
ilcreasedwith period of fallow (Figure 1). The cajanusand canavaliagaveslightly
higher effect on soil organicmatterthan other fallow crops.They also increasedthe
organicmattercontentby 95 and'77Yo,
respectivelywhen comparedwith the valuesat
pre-cropperiod. Likewise,they addedto the soil 360 - 390 kg Nlha ard 25 - 28 kg
P2O5lha
afterthreeyearsof fallow.
112
-..-
Figure 1: Effect ofleguminous
periods
fallow crops on soil properties at different fallow
N Prc{rop
E 1st yeaf
- 2nd year
B 3rd year
91
OO
<8
E
2
3.2 F,arLeaI TissueNutrient Concentration
Table 2 showsthe concentrationof someplant nutrientsin maize leaf tissueat 4 and 8
was
weeksafterplantingsampledfrom the unfertilizedplots. Nutrient concentration
highestin plantsgrown after mucunaand cajanusfallow. The effect ofnatural bushand
..ot o..-u fallow was lower than that of otherlegrunefallow. cajanus,mucunaaad
canavaliahighly improvedthe concentrationofphosphorusand magnesiumin the
plant. On the whole, nitrogenin the leaf tissuewas stronglycorrelatedwith matzeyield
ir =0.93).Whereas,the coefficientof corelation betweenphosphorusandyield was
andyield waslow (r = 0.30)'
medium(r =0.77),while thatbetweenpotassiurn
3.3 Maize Yield
The effect ofthe variousfallow cropson maizeyield is shownin Figure2. Cajanus,
mucunaand canavaliawere highly promising. The leasteffect was obtainedfrom bush
Applicationof 50kg N/ha NPK 20-10-10on the second
followedby centrosema.
gavesignificant(p : 0.05)
fallowedsubplotsoccupiedby naturalbushandcentrosema
113
increasein maizeyield. Theyield increased
by 67 and69%respectivelyovertheyields
yield
on the fallowed plots without fertilizer. However, there were 14%, l2yo and9%;o
increasesfrom canavalia,mucuna and cajanus,respectivelywhen fertilizer was
applied.This indicatesthat additionaluse of fertilizer on soil fallowedwith the later
three cropsmight not be really necessary.Whereas,additionalfertilizer input was
requiredafter putting the land to fallow for threeyearswith naturalbushre-growth.
This will attractextracoston productionandthereforereducesfarmer's profrt.
Table 2: Effectoffallow crooson thenutrientconcentration
in maizeleaftissue.
Treatment
N, o%
WAP+
4
P, o/o
E48
K,o/o
Ca,o/o
Mg,o/o
48
48
4E4E
Bush
2.04a 1.65c 0 28b 0.22b 3.55b2.54a 0.21a 0l6b
Cenüosema2 10a 1.68c 0.25b 0.27b 2.85b2.04b 0.22a 0.15b
Canavalia 2.25a 1 . 8 5 b 0 . 3 3 a0.29b 3.25b2.72a 0.2Ea 021a
2.38a 1.84b 0 32a 0.34b 3 20b 2.5Ea 0 2 7 a 0 2 2 a
Mucuna
Cajanus 2.30a 2.04a 0.30a 0 . 5 1 a3.68a2.32b 0.30a 0.20a
Zn,o/o
0 0 5 b 0 . 1 2 a4 0 b
0.06b 0 09b 55a
0 10b 0.13a 67a
009b 0.13a 65a
0.14a O.l2a 58a
60b
50b
88a
92a
90a
* WAP - weeksafter planting
Figureshaving the sameletters in the column are not significantly different at p = 0.05
Figure 2: Effect of some leguminous fallow crops on maize yield.
L S O ( 00 5 )
Bush
Cenfos€ma
Canavalia
3.4 Nutritional Values
In some parts of Nigeria, the seedsof cajanusare edible and serve as proteia
supplementin humanand livestocknutrition. However,the nutritional value of mucuna
seedshas not beenfully investigated.Mucuna seedscontail high value of oil and
protein,which would makethe crop to be useful in humanatrdanimalnutrition and
would probablybe of medicinalvalues.From our own investigationmucunacontains
potassiumandlessthan 7o/o
total ash,2.6Vo
aboü 2IVoprotein,3.8%crudefibre,4.2%o
of other important elements.Canavaliaon the other hand, contains abont ll.3%;o
protern,9.6Yocrudefibre, 40Ätotalash.Further investigationson the nutritional values
ofthe two cropswouldbe required.
1t4
3.5 MicrobialPopulation
Effect ofsome ofthe fallow cropson the populationofsoil microbesis presentedin
populationcountswereobserved
figure 3. The leastfungi, bacteriaandactinomycetes
in soilsfrom the bushfallow plot. Fungipopulationdueto canavaliawastwice ofthat
from mucuna and cajanuswhen addedtogether. Cajanuscajan gave the highest
(108 * 16s;andwas followed by that from
populationofbacteria and actinomycetes
canavalia(90.5x 105).
Figure 3: Effectoffallow cropson microbialpopulationin the soil.
12
3s
e^
2
8on
3 1oo
e80
9-^
E
E4A
Em
E0
Bush
4
Discussions
The natural bush fallow comprised of heterogenous plant population predominantly
occupied by Pannicum mmimum. Although, Centrosema brasiliensis is a leguminous
crop, it produced the least biomass (2.3 1 - 2.98 kglmz) and could not regeneratewell in
the following season,Cajanus fallow was most convenient to handle as a fallow crop. It
could even regenerate if it was cut back in the following growing season. It provided a
dense and wide canopy and produced high amount of biomass (4.5-6.8 kg/mz). It
completely formed 70%ogroundcover in the first year and about 95Vo groundcover in
the second year while, the canopy and leaf falls (serving as mulch) smothered the
weeds effectively at the end ofthe second year. The crop suppressedweed biomass and
reduced it to about 40%;oand 15% when compared with centrosema and canavalia,
resoectivelv.
115
The canavaliaalsohas ahnostsimilar characteristics
as for the cajanus.However,it
was more difficult to managethan cajanuswhen put to fallow. The crop is not as
popularwith farmersascajanusandthe seedshavenot yet beenintroducedto Nigerian
farming communities.Mucuna,like cajanus,was highly effectivein improving soil
fertility and increasingcrop yield. It producedhigh amountofbiomass (4.S - 5.6
kg/mz).It is an arurualcrop but would regeneratein subsequent
yearsand would be
adaptedas fallow crop if well managed.However, it createda great difficulty in
managingit for threeyems.Mucunawas ableto form an effectivegroundcoverasfrom
10 weeksafter planting.It effectivelysuppressed
weedsevenbetterthan cajanusand
canavaliain the first year fallow period.
The generalattributesofthe fallow cropsasdiscussed
abovecontributedprincipallyto
their effectiveness
whenusedas sourceofsoil fertility enhancement.
Cajanuswasable
to add more organic matter to the soil than other fallow crops whereas,mucuna
improvedthe CECofthe soil betterthantherestfallow crops.
5
Conclusions
Plantingofimprovedfallow cropsenlancedsoil propertiesandyield ofmaize. In term
ofeffectiveness,the fallow cropscouldbe arrangedin the ascendingorder- cajanus,
mucuna,canavalia,centrosemaandbush.Cajanusfallow was easierto maintainand
could be left fallow for three or more years.In order to obtain optimum crop yield,
cropping of land left fallow for three yearswith natural bush and centrosemarequted
more fertilizer input than when cajanus,mucunaand canavaliawereplanted.
6
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