Effect of Tillage Methods and Fertilizer Applications on Amaranthus curentus in Nigeria
Christopher O. Akinbile
Mohd Suffian Yusoff
The response of Amaranthus to varying fertilizers application and different tillage practices for optimum vegetable production were investigated. This was to increase productivity for food security and reduced growing insecurity to achievable minimum. The optimum level of fertilizer applications and best tillage methods for improved productivity is unknown hence this study. Four treatments based on fertilizer applications viz; nitrogen, phosphorus and potassium, (N-P-K, 15-15-15), manure, peat and urea were administered on the vegetable in four different tillage methods namely: zero, bed, heap and ridge using standard procedures. The treatments were replicated using Randomized Complete Block Design (RCBD). Agronomic and soil parameters were determined and subjected to statistical analysis. From the study, responses of measured agronomic parameters showed that the ridge tillage method with N.P.K fertilizer application gave optimum yield among the treatments. The vegetables in this treatment had average leave length, root depth, plant height and Leaf Area Index (LAI) values of 29.8, 9.9, 143 and 13.8, respectively all at 8 Weeks After Planting (WAP). These were highest when compared with results from other treatments. Values of soils nitrogen, phosphorus and potassium were 0.29, 8.66 and 0.22 mg kg-1, respectively while calcium and magnesium were within acceptable limits for crop development with values ranging from 2.9 to 8 mol kg-1 and from 2 to 5 mol kg-1, respectively. Statistical analysis among agronomic parameters showed significant difference (p<0.05). Ridge tillage and N.P.K application affected biomass yield and growth of Amaranthus cruentus considerably and is therefore suggested for increased vegetable productivity in Nigeria.
Received: November 07, 2010;
Accepted: January 01, 2011;
Published: March 28, 2011
Amaranths cruentus belong to the family of vegetable call Amaranthaceous
and it is grown as a vegetable in western Africa and especially in Nigeria.
Amaranth species is rich in proteins minerals, containing 15-22% protein,
3.0-11.5% fat and 9-16% dietary fibre depending on cultivation techniques and
environmental effects (Tosi et al., 2001). Other
major consumers, according to Abu Ziada et al. (2008)
come from other parts of Africa, China, India and Italy. Amaranths is
also of significant importance to the Asian region because of the taste, colour
and textures, they provide in meal however, the main constituent is starch 48-62%
with small granule size which can easily be dispersed (Colla
et al., 2006). It was also reported by Abu Ziada
et al. (2008) that the green leaves of Amaranthus were rich
in water, energy, fats, proteins, minerals, amino acids and carotenoids. Protein
deficiency is one of the major problems confronting the developing countries
of the world. This may be due to the fact that animal source of protein is by
far too expensive for an average household in the developing nation. Vegetable
which would have being grown throughout the year, was not as a result of shortage
of water supply during the dry season. Vegetable contains 80 to 95% of water
and because of this, its yield and quality deteriorates rapidly when subjected
to water stress. Hence, for a good yield and high quality, irrigation is essential
to the production of most vegetables (Kemble and Sanders,
2000). If water shortages occur early in the crop development, maturity
may be delayed and yield reduced. However, if moisture shortage occurs late
in growing season, quantity is often reduce but the overall biomass yield may
not be affected (Allen et al., 1998). Tillage practices
have been reported to have significant impact on crop production (Awe
and Abegunrin, 2009). Tillage and crop can play a role in creating or removing
environmental stimuli that regulates germination of seeds (Steckel
et al., 2007; Lal, 1991). Producing early
maturing vegetables in commercial quantities in Nigeria required among other
factors, fertilizer application in sufficient quantities and in accordance with
tillage preparations. The use of soil amendments is mainly to improve crop yields
while improved yields results from improved nutrient status in soil and other
soil properties such as organic matter (Mungai et al.,
2009). The response of ground vegetation to fertilization has received less
attention especially in the tropics although their contribution to the annual
nutrients cycling is great (Ong et al., 2008).
Olaniyi et al. (2008) reported that there is
limited preliminary information on fertility requirements of Amaranths. The
effects of different types of fertilizers and tillage operations have on the
development and growth of amaranths is unknown hence this study. This is a clear
indication that there exists paucity of information on the effects of tillage
practices and fertilizer application on the vegetable performance. Therefore,
the objectives of the study were to determine the responses of Amaranthus
to various types of fertilizer application and at different growth stages, determine
its response to different tillage methods under standard and environmental conditions
and to make recommendations to farmers and other end users about the effects
of these findings on the vegetable yield in Nigeria for optimum production.
MATERIALS AND METHODS
Description of the project site: The study was conducted from March
through June, 2010 at the teaching and research farm of the Department of Agricultural
Engineering, Federal University of Technology, Akure, Ondo State, Nigeria. Akure,
the capital of Ondo State which lies between latitude 5°45 and 8°15
North and longitudes 4°30 and 6° East in the rain forest belt
of the tropics. Akure has a tropical climate with distinct wet and dry seasons.
A warm rainy season spans April to October followed by a hot dry period from
November to March. The annual rainfall ranges from 1405 to 2400 mm with August
as the wettest month and November as the driest month. The average monthly temperature
is 26.5°C; a maximum temperature of 36°C is recorded during the dry
season while the minimum temperature is about 27°C. The city has humidity
range of 56 and 59% during the dry season and about 51-82% during the wet season
with average sunshine hours of 4.5 h which varies between 1.8 hours and 5.9
hours. The shortest hours are in August while the longest is in September. Generally,
the topsoil is composed of sand varying from 76-85%. Profile (0-40 cm) analysis
from a number of locations within the study is clay loam (Akinbile,
Land preparation and experimentation: The site was prepared using conventional
equipment for the experiment. An area of 5x5 m2 was selected and
four treatments and four replicates using Randomized Complete Block Design (RCBD)
were adopted. The distinction between the treatments was due to tillage practices
while each of the four replicates in each treatment contained the four fertilizers
administered in pre-determined quantities. Treatment A (zero or no till), B
(bed), C (heap) and D (ridge) were replicated in four plots with each plot having
NPK, manure, peat and urea administered to them in 2.0 kg ha-1 and
in line with convectional practices (Olaniyi et al.,
2008). Normal irrigation (in form of rainfall) was applied to each of the
treatments in the same quantities to observe its effects on varying soil and
fertilizer applications. Amaranthus cruentus seeds were obtained from
the Agricultural Development Project (ADP) office Akure, Ondo state and the
seedlings were air-dried and treated before planting by broadcast method. Seed
germination took place within one week after planting and thinning was done
2 Weeks After Planting (WAP). Soil analysis was performed to determine the percentage
of residual constituents of some of the ions such as Nitrogen (N), Phosphorus
(P), Potassium (K), Magnesium (Mg) and Calcium (Ca) organic matter and the pH.
Also, soils classification was determined while its moisture content was
monitored from 3 WAP and measurements taken. Agronomic parameters such as plant
height, root depth, Leaf Area Index (LAI), number of leaves, leaves length and
width were measured throughout the growing season of Amaranthus using
standard and convectional procedures.
Statistical analysis: All the agronomic parameters were measured from 3 Weeks After Planting (WAP)and the results were subjected to statistical analyses using ANOVAt test procedure on Excel software spreadsheet considered at 95% level of significance (p<0.05).
RESULTS AND DISCUSSION
Soil moisture regimes: The average soil moisture content in all the
four treatments from 3 Weeks After Planting (WAP) was presented in Table
1. There were noticeable soil moisture increased from 10 to 40 cm depth
in all the treatments indicating a well-watered scenario throughout the experiment.
In 3 WAP, soil moisture ranged between 0.98 and 1.42 cm down the profile but
there was a reduction a week later down the profile. This may be due to the
metabolic activities picking up at the vegetative stage of crop development
and since the roots will have to access water and nutrients, reduction in soil
moisture was probable. This was similar to the observations of Akparobi
(2009). From 5 WAP through 8 WAP, a relative water balance in the profile
was maintained, an indication of saturation and field capacity status of the
soil. Since water applied was not regulated, availability of more moisture for
the vegetable metabolic activities was possible. This was similar to the opinions
of Steckel et al. (2007) in one of his studies.
Having more quantities of water as the depth increases was also an indication
of the fine soil aggregates down the profile which permitted smooth infiltration
and appreciable retention of water as soil depth increases. Akande
(2006) showed similar observations in his findings. Lack of water on soil
surface as runoff and low volume in the 10 cm profile also indicated suspected
presence of sandy loam soil which permits free flow of water and supports enhanced
crop development due to presence of nutrients from remains of dead leaves. Sandy
loam is known for it good aeration and porosity capacities hence its ability
to permit free water movement within the profile (Allen et
Soil physical and chemical properties: Results of the soils physical
and chemical properties of the study area were as shown in Table
2. The pH values ranged from 5.66 to 5.82 indicating that the soil was acidic.
This promoted good crop development and growth as vegetables generally thrives
well on mildly acidic soil. Below this range poses severe danger for the crop
development and above may not be too harmful but definitely takes its toll on
its optimum yield.
Several researchers including Mungai et al. (2009)
have reported the beneficial effect of soil acidity on shallow-rooted crops
such as vegetables for optimum growth and development. Organic matter was within
the range 3.00 and 3.65 acceptable for excellent vegetable growth. The remains
of dead leaves, earthworms and other animals may have enriched the soils
organic matter. The area was also allowed to fallow for four years which may
also be responsible for high organic content. This increased the soil nutrient
and promoted good crop development with the different types of fertilizer administered
to the soil. Buah and Mwinkaara (2009) reported the
influence of nitrogen-composed fertilizer on the organic content of the soil
as to promote germination and plants development. While the soils
nutrients such as phosphorus (P), potassium (K) and calcium (Ca) which had values
ranging between 6.29 to 10.15, 0.19 to 0.27 and 2.90 to 8.0 mol kg-1,
respectively were expectedly within acceptable limits for crop growth, the soils
profile was also good for genuine crop growth. N ranged between 0.26 and 0.32
mg kg-1 was also within desirable limit in soil for optimum crop
production. Ong et al. (2008) remarked that under
repeated short rotations of fast growing spieces such as vegetables, N and P
are the two most important nutrient elements determining the productivity of
most tropical plantations as base cations are important in highly acidic soils.
The results using the United States Department of Agriculture (USDA) textural
triangle indicated a sandy clayey soil with the average sand composition of
62%, clay 27% and silt 12%. This soil class have high porosity and permeability
profiles in the aggregates thereby enabling easy access of roots, especially
shallow roots of vegetables to quick water and nutrient uptake, good aeration
and also excellent drainage possibilities. Polthanee and
Changdee (2008) reported that significant interaction effects was mostly
probable between root management and fertilizer application in a soil constituents
such as this due to the porosity and degree of aggregates present due to its
Plant height: Figure 1 showed the average plant
height with weeks after planting in all the treatments. The same growth was
observed in all the treatment in the 3rd and 4th week after planting. After
5 WAP, the effect of fertilizer application and tillage practises was visible
as the weeks progressed. It was evident that treatment D (ridge tillage) had
the pronounced response to crop growth. The distinction in its height was visible
despite its initial slow start especially within the first 4 WAP. This may be
due to the effect of tillage which enabled the roots reach out to nutrients
and water for development when compared with other treatments. The distinction
began to manifest just after the 4 WAP when the height reached 17 cm compared
with the ones in other treatments that was 20 cm (Fig. 1).
|| Average plant height and Weeks After Planting (WAP) in all
the four treatments
By the time it was 8 WAP, the distinction was very obvious with more than
20 cm difference in height. At 8 WAP, average plant height in D was 143 cm while
the average plant heights in treatments A, B and C was 120 cm. Similar observations
were made by Makinde et al. (2010), Olaniyi
et al. (2008) and Akande (2006) all of whom
reported that the application of each of N and P significantly increased the
plant height, number of leaves and fresh shoots. Fertilizer and its interaction
with proper tillage have significant effect on total plant height, root depth
and length of leaf. Awe and Abegunrin (2009) and Steckel
et al. (2007) also agreed that tillage played a role in the behaviour
of the agronomic parameters, especially the plant height development. This was
also an indication that degree of soil aggregates, pulverisation, porosity and
pore spaces within the soil profile have tremendous effect on roots accessibility
to water and nutrients uptake hence pronounced and noticeable development. It
was reported by Oryokot et al. (1997) that Amaranthus
densities were much higher in till environments compared with no-till environments
due to the roots easy accessibility to water and nutrients uptake
from the soil. Though urea, manure and peat also supported plant height development
(Fig. 1), the effect of NPK was mostly distinct on the overall.
Modisane et al. (2009) reported the considerable
influence of NPK on Amaranthus in their studies which were similar to
the findings of this study thereby justifying the visible effect of NPK on the
vegetable from this study.
Root depth: Figure 2 showed the average root depth
compared with the weeks after planting during the experiment. Treatment D was
clearly distinct as the depths of roots were obviously the deepest when compared
with the remaining treatments. From 3 WAP, all through than growing season,
roots in D were deeper than in other treatments. It was 4 cm in 4 WAP while
others were lower with the exception of C which was closer (3.6 cm) perhaps
due to tillage method (heap). The tendency to reach out to higher quantities
of nutrient and water was more in treatment D compared to others hence the root
elongation. It was also inferred that the ridge tillage method may have affected
the crop greatly, having responsible for the roots deep penetration into the
soil. Similar observation was observed by Afolayan et
al. (2004) in their study. The maximum root depth of 9.9 cm was recorded
in D while the least of 8 cm was recorded in A at 8 WAP. This was unexpected
due to the fact that the tillage method in A was zero tillage and so the root
encountered greater difficulty in accessing nutrients and water for optimum
sustainability. However, getting to 8 cm depth may be due to the nature of the
soil (sandy clay loam) which still supported crop development due to the loosely-packed
nature of the topsoil. Aon et al. (2001) disagreed
with the observations but Haque et al. (2001)
reported similar results.
|| Average root depth of Amaranthus with Weeks After
Planting (WAP) in all the treatments
Leave length: From Fig. 3, it was evident that treatment
D had the averagely longest leaves when compared with other treatments. The
ridge tillage method allowed the roots access to the fertilizer applied (NPK)
which take up nitrogen, phosphorus and potassium necessary for crops photosythesis
which gave the green colouration and elongation to the leaves. The maximum leave
length was 27.8 cm found in D while the minimum was recorded in B, treatment
with bed tilage method with the value 24.8 cm at 8 WAP. Treatment B was particularly
neagatively dinstict from the rest despite being bed tillage method. This may
be due to the unhealthy competiton and demand for nutrients by the Amaranthus
planted on bed hence the manifestations on the length of the leaves. This was
however, in sharp contrast with other treatment, particularly in D where the
crops were planted in rows along each ridge, each plant stand accessing basic
needs with minimal competiton from other crops other than weeds which were being
removed periodically. The pronounced effect of soil macroporosity was evident
in the development of leave length. Hearda et al.
(1988) reported that increased access to the soil nutrients by the roots
was evident on the leaves development in a tilled environment.
Leaf Area Index (LAI): Figure 4 showed the relationship
between the leaf area index (LAI) and the weeks after planting (WAP) in all
the four treatments. The LAI values in treatment D were disntict throughout
the experiment due to the high values of LAI from 5 WAP till the end of the
study. LAI values in 5 WAP was 13.8, about 2.1 over other values in other treatments
in the same WAP. The development increased and maximum LAI values was reported
in 8 WAP (34.5) and still remained the highest during the study. Since other
agronomic parameters such as plant height, no of leaves, root depths were greater
in D as compared with other treatments, it could be inferred that LAI should
not be an exception as the nutrients from soil through the roots were accessed
by plant shoot for development. The formation of canopy shading for denser foliage
cover is a function of well developed foliages (leaves) which is also dependent
on the accessability of the plant to water and nutrient uptake in sufficient
quantities. Akinbile (2010) reported similar results
in NERICA rice (New Rice for Africa) under similar conditions. Amaranthus
currentus in treatment D were planted on ridge and applied with NPK fertilizer
and when compared with other treatment methods, it proved to be the best in
response to tillage methods and fertilizer application during the growing season
of the crop. Apart from tillage practises and fertilizer applications, other
factors that may be responsible for the high LAI values according to Akinbile
et al. (2007) included; photosynthesis, direct incidences of solar
radiation, weed control, water application, seed variety and cultural practises.
|| Average leave length with Weeks After Planting (WAP) in all
|| Leaf Area Index (LAI) vs weeks after planting in all the
The results from this study have shown that the type of tillage method and
type of fertilizer applications has direct implications on plant height, root
depth and leaves length of Amaranthus currentus. At 2 WAP, there were
significant differences in stem girth between ridge and other tillage methods
but difference seems to be not significant when compared with others tillage
methods. For other weeks (3 to 8 WAP), similar trend was observed indicating
that ridge tillage method and N.P.K application gave optimum and desirable results
in the production of Amaranthus cruentus. This showed clearly that ridge
method was the best in the given circumstance for producing vegetables such
as Amaranthus and may be due to the fact that ridging reduces soil density,
increased soil macro porosity thereby reducing conduction of heat into the soil
during the day. Although in other tilled plots (bed and heap), considerable
good performances were observed on the total parameters, the crop arrangement,
leaves overlay and competing demand for nutritients and food denied them improved
performance as in ridge method. This is because there was a better uptake of
nutrient especially phosphorus which resulted due to mineralization and organic
matter when mixed with soil during tillage (Lal, 1991).
However, loosening of soil enabled root elongation and better uptake of nutrient
below the surface due to downward movement of the absorbing roots. Afolayan
et al. (2004) and Guerif et al. (2001)
reported similar results that was observed that plants in tilled plots performed
better than untilled plots, especially with respect to leaf area, root density
and shoot yield. Also, the composition of nutrients needed for increased development
was more in NPK, due to its organic nature when compared with other types of
fertilizer used such as manure, peat and urea (Olaniyi et
al., 2008). Peat is the accumulation of partially decayed vegetative
matter and since it store nutrients although not itself fertile hence its effect
in catalyzing crop development may not be visible as compared with other fertilizers.
Urea on the other hand, had highest nitrogen content of all solid nitrogenous
fertilizers in common use but its addition failed to improve the enhancement
of already-degraded soil, particularly in an area prone to continuous cropping
due to limited land availability, hence its limitation (Akparobi,
|| Correlation coefficient of different physiochemical variables
from the study data
|Significant at *p<0.05; LL = Leaf length, RD = Root depth,
PH = Plant height, LAI = Leaf area index
However, as the latter (peat and urea) would not leave residue behind in the
soil due to their inorganic nature, NPK residue in form of salts causes injuries
to the soil, hasten depletion and on the long run cause severe injuries to the
crops. Over irrigation to dissolve the salts residue and flush away from farmlands
has been done over the years to mitigate this.
Test of significance of the observed correlation coefficients: The significance of the observed correlation coefficients has been tested and the results were as shown in Table 3. Out of the total 6 correlations found between two parameters, 2 were found to have significant at 5% level, (r>0.7). However, there was no negative correlation. The correlations observed existed between Plant Height (PH) and Leaf Area Index (LAI) (0.72), Root Depth (RD) and (PH) (0.68) and Leaf Length (LL) and RD (0.51), respectively. Others were between LL and PH (0.69) and LL and LAI (0.48). The only highly significant correlation was between RD and the LAI (r = 1). In all the parameters tested using t-test correlation analysis, there were significant differences in all the parameters considered at 95% confidence interval also confirming the influence of tillage methods and fertilizer type application on growth and yield of Amaranthus curentus.
The pronounced effects of tillage practices and fertilizer application on the growth, development and yield of Amaranthus were visible in the study as shown in the results. From the study, it was evident that ridge tillage method and NPK fertilizer applications were most suitable for the optimum production of the vegetable both as food crop and also for economic considerations. The responses of plant height, leaves numbers and length pointed to this fact. These signs were clearly distinct as from 8 WAP and throughout the experiment when compared with the responses of the crop in other treatments and replicates. This may be attributed to the fact that ridging reduces soil density, increases soil macro porosity thereby reducing conduction of heat in the soil during the day. Ridging facilitated uptake of nutrients especially phosphorus which resulted due to mineralization or organic matter when mixed with soil during tillage, loosening of soil enables root elongation and better uptake of nutrient by absorbing roots. It could be concluded that the use of ridge tillage and with NPK fertilizer has proved to be most effective because it stimulated profuse shoot growth and massive root development of Amaranthus. Consequently, it increased nutrients composition of plant hence, increases crop growth and yield.
The authors are grateful to Mr. A.A. Akinbanjo for his assistance in data collection and to Third World Academy of Science (TWAS) for the provision of one year Post-Doctoral fellowship (FR Number: 3240223476) and the Universiti Sains Malaysia (USM) that enabled him utilize the fellowship for research study.
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