ABSTRACT
Three field experiments were conducted at the Teaching and Research Farm of the
Department of Crop Science, Faculty of Agriculture, University of Nigeria, Nsukka. In the
first experiment, the effects of fertilizer-N application and cutting management on
establishment, growth and yield of guinea grass (Panicum maximum) were investigated.
The experiment was a 4 x 4 factorial laid out in a randomized complete block design with
three replications. Treatments comprised four levels of Nitrogen of 0, 150, 300, and 450
kg N ha-1 and four harvesting frequencies of 3-, 6-, 9- and 12-weekly intervals. A second
experiment was conducted using guinea grass/verano stylo (Stylosanthes hamata) mixed
swards. The experiment was a 3 x 3 x 2 factorial laid out in a randomized complete block
design with three replications. Treatments comprised three swards types (pure grass, pure
legume and grass-legume mixed swards), three harvesting frequencies of 4-, 8-, and 12-
weekly intervals and two levels of nitrogen at 0, and 300 kg N ha-1. The third experiment
was conducted to evaluate the effects of two cutting frequencies (4- and 8-weekly
intervals) on the growth and yield of four legumes (Lablab purpureus, Stylosanthes
hamata, Centrosema pascuorum and Stylosanthes guyanensis) and four grasses (Sorghum
almum, Panicum maximum, Chloris gayana and Andropogon gayanus). Basal applications
of muriate of potash (75 kg K ha-1) and single superphosphate (44 kg P ha-1) were also
made by broadcasting in all the experiments. In the first experiment, tiller number per
square metre, plant height and grass dry matter yield were increased by 44%, 6% and
53%, respectively, during the establishment year when fertilizer-N rate was increased from
0 to 450 kg N ha-1. Grass dry matter yield was increased by 41% and 149% when the
interval between cuts was increased from 3- to 12-weekly intervals at the first and fourth
harvest years, respectively. Plots cut at 3- or 6- weeks intervals exhibited much greater
weed proportion than those cut 9-, or 12-weekly intervals. Increasing the interval between
harvests from 3 to 12 weeks increased the proportion of stem relative to leaf blade in the
grass swards. The proportion of inflorescence, plant height and dry matter percentages,
were generally increased by increasing the interval between cuts. Tiller number decreased
with increasing interval of cut. The total annual herbage dry matter yield was increased by
32% and 48% in 2001 and 2004, respectively, when fertilizer-N was increased from 0 to
450 kg N ha-1. Increasing the N rate from 0 to 450 kg N ha-1 increased the proportion of
stem relative to the leaf blade in the grass swards. Plant height and tiller number were
increased with increase in N application while the dry matter percentage was generally
decreased with incremental application of nitrogen. A combination of 12-weekly interval
of cut with 300 kg N ha-1 gave a significantly higher forage grass herbage dry matter yield
compared with the values got from the 3- or 6-weekly interval combined with any N rate.
Fertilizing at 300 or 450 kg N ha-1 when combined with cutting at 9 or 12-weekly interval
between cuts was more effective in suppressing weed growth and weed dry matter as a
proportion of the total herbage dry matter. The N % and crude protein contents in the leaf,
stem and in total herbage dry matter decreased significantly with increasing interval
between cuts. Yield of crude protein in the total herbage was significantly higher when
cutting was done every 6 weeks compared with when done every 9 weeks. Nitrogen
fertilizer x cutting frequency interaction effects on N %, crude protein contents and crude
protein yields in the crop fractions and in total herbage dry matter were not statistically
significant. On the average, the crude protein and mineral contents were higher in the leaf
fraction than in the stem and inflorescence fractions. In the second experiment, herbage
production was 16% and 69% higher on guinea grass/stylo swards in 2006 and 2007,
respectively, compared with the yields for the pure guinea grass swards. Grass dry matter
yield as a proportion of the total herbage dry matter was significantly increased from 45%
vi
to 61% in 2007 with 12-weekly cutting interval compared with 4-weekly interval. The
weed proportion was significantly reduced from 28% to 19% with the infrequent cutting
interval of 8-weeks compared with the 4-weeks in 2007. Cutting frequency did not
influence the proportion of verano stylo in 2006 and 2007. However, the legume dry
matter yield was generally increased with longer intervals between cuts. The effects of
fertilizer-N rates on the proportions of grass, legume and weed in 2006 and 2007, were not
statistically significant. The total herbage dry matter yield was significantly higher in
guinea grass/stylo swards when cutting was done at 8-weekly interval compared with sole
guinea grass or verano stylo at any interval between cuts. Crude protein yield of the guinea
grass/stylo sward was higher than that of pure guinea grass sward by 8 %. In the third
experiment, Stylosanthes guyanensis had the highest dry matter yield among the four
legumes in 2007 when 8 weeks interval between cuts was employed. Among the four
grasses, Chloris gayana produced significantly greater dry matter yield than Sorghum
almum but had a similar yield value with Panicum maximum or with Andropogon gayanus
in 2006. Andropogon gayanus yielded more than Chloris gayana but had a similar yield
value with Sorghum almum or with Panicum maximum in the first harvest year. Cutting
interval did not influence the extent of legume cover. However, the extent of grass cover
was increased by 30% when the interval between cuts was increased from 4 to 8 weeks.
Weed cover in the legume plots was not influenced by cutting management. However,
weed cover in the grass plots was significantly depressed by 21% with increased interval
of cut from 4 to 8 weeks. The dry matter percentages among the grasses and the legumes
were generally increased by increasing the interval between cuts. In 2006, Stylosanthes
hamata had significantly higher dry matter content among the legumes than Lablab
purpureus and Stylosanthes guyanensis but did not differ with Centrosema pascuorum. In
2007, Lablab purpureum had significantly the least percentage dry matter compared with
the other legumes. Stylosathes hamata had higher percentage dry matter than Centrosema
pascuorum but did not differ with Stylosanthes guyanensis. Grass dry matter content did
not vary among the grass species in 2006. In 2007, Sorghum almum had higher (P<0.05)
dry matter content than Chloris gayana but had similar value with Panicum maximum or
with Andropogon gayanus.
TABLE OF CONTENTS
CERTIFICATION … … … … … … … …
… … … ii
DEDICATION … … … … … … … … …
… … … iii
ACKNOWLEDGEMENT … … … … … … …
… … … iv
ABSTRACT … … … … … … … … …
… … … v
TABLE OF CONTENTS … … … … … … …
… … … viii
LIST OF TABLES … … …. … … … … …
… … … xi
CHAPTER ONE: INTRODUCTION … … … …
… … … 1
CHAPTER TWO: LITERATURE REVIEW … … …
…
… … … 5
Guinea Grass (Panicum maximum Jacq.) … …
…
… … … 5
Verano Stylo (Stylosanthes hamata) … … … … … … 7
Lablab (Lablab purpureus) … … … … … … … … 9
Centrosema pascuorum … … … … … … … … 10
Stylsanthes guyanensis (Cook stylo) … … … … … … 10
Sorghum almum (Columbus grass) … … … … … … … 11
Rhodes grass (Chloris gayana) … … … … … … … 11
Gamba grass (Andropogon gayanus) … … … … … … 12
Potentials in the use of legumes for increasing
profitability and promoting sustainability in pasture
production systems
… … … 12
Pasture grass response to defoliation management
…
… … … 15
Pasture legume response to defoliation management
…
… … … 19
Pasture grass response to fertilizer-N application …
…
… … … 20
Pasture legume response to nitrogen fertilizer …
…
application
… … … 23
Pasture grass x legume response to nitrogen fertilizer
…
… … … 23
viii
Application
Pasture grass x legume response to cutting frequency
…
… … … 24
Pasture grass and legume response to cutting
management x nitrogen fertilizer interaction
… … … 25
CHAPTER THREE: MATERIALS AND METHODS …
…
… … … 27
Experimental site … … … … … … … … … … 27
Experiment 1: Effects of nitrogen fertilizer application and
cutting management on the establishment, growth
and
yield of guinea grass (Panicum maximum)
… … … 27
Land preparation … … … … … … … … … … 27
Planting and Treatment Allocation … … …
…
… … … 27
Data Collection … … … … … … … … … … 28
Experiment 2: Effects of nitrogen fertilizer application and
cutting management on the establishment, growth
and
yield of guinea grass-verano stylo mixed swards
… … … 30
Land preparation … … … … … …
…
… … … 30
Planting and Treatment Allocation … … …
…
… … … 30
Data collection … … … … … …
…
… … … 31
Experiment 3: Effect of cutting frequency on the growth
and
yield of four selected forage legumes and four forage
grasses
… … … 31
Statistical Analysis … … … … … … … … … 32
CHAPTER FOUR: RESULTS … … … … …
… … … 33
Experiment 1: Effects of nitrogen fertilizer application and
cutting management on the establishment, growth
and
yield of guinea grass (Panicum maximum)
… … … 33
Experiment 2: Effects of nitrogen fertilizer application and
cutting management on the establishment, growth
and
… … … 86
ix
yield of guinea grass-verano stylo mixed swards
Experiment 3: Effect of cutting frequency on the growth
and
yield of four selected forage legumes and four forage
grasses
… … … 133
CHAPTER FIVE: DISCUSSION … … … … …
…
… … … 157
CHAPTER SIX: SUMMARY AND CONCLUSION …
…
… … … 171
RECOMMENDATION … … … … … … … …
… … …
173
REFERENCES … … … … … …
… … … 175
APPENDICES … … … … … … … … … …
… … … 197
CHAPTER ONE
INTRODUCTION
In Nigeria, feed deficits and low quality of the available feed, particularly during 5
to 7 months of the dry season are major constraints for optimum livestock production from
the savanna rangelands (Omokanye, Kalla, Alawa and Otchere, 1998). Livestock
production depends closely on the availability of animal feed of high quality. Availability
of high quality feed is influenced by climatic conditions, plant species and stage of
maturity, soil, the level of inputs and by management (Muhammad, Hena, Agishi and
Olorunju, 2002; Enoh, Kijora, Peters and Yonkeu, 2005).
Smallholder producers of ruminants, particularly cattle, sheep and goats, in
Nigeria rely on unimproved natural pasture as the main feed source, backed up with crop
residues after harvest (Bamikole, Akinsoyinu, Ezenwa, Babayemi, Akinlade and
Adewumi, 2004). The animals in consequence grow slowly, produce little milk and
reproduce at long intervals. This problem of inadequate feeding stuff is further aggravated
particularly in the dry season when grassland productivity is low (Oloyo and IIelaboye,
2002). The present poor production potential of pastures could be attributed to poor soil
fertility and to poor management (Dev, 2001).
Most pastures in Nigeria lack proper management because of poor defoliation
frequency and lack of proper fertilization. Pastures are often subjected to burning and
extreme grazing which have been shown to result in serious deterioration of herbage (Dev,
2001). It has been noticed that economic factors make a viable commercial livestock
industry imperative, needing the establishment of suitable sown pasture and feed lots to
meet the higher nutritional needs of more productive animals (Bamikole et al., 2004).
Increments in fodder production can be achieved by expansion of land areas under natural
pastures or by increasing yields per unit land area. With the present trend of competitive
land use, increasing forage production through expansion of land area of natural pasture is
hardly feasible as a result of the demographic changes (Muhammad and Abubakar, 2004).
In the emerging shift in animal management systems towards confinement because of the
pressure on land, a strategic forage harvesting and management system suitable for
confined ruminant livestock and which will guarantee a regular supply of high-quality
forages to these livestock is required (Bamikole et al., 2004). Improvement of feed
availability for the future requires development of sown pastures that are to be sustained
under intensive systems of management. Intensive production system involves the use of
1
2
forage species that must prove their superiority in terms of their bulk productivity (dry
matter yield per unit area), palatability, chemical composition, nutrient availability,
persistence under defoliation regimes and inclement climatic conditions, competition and
compatibility with other forages in the pasture ecosystem (Muhammad and Abubakar,
2004). Improved grasses and legumes have been recommended for intensive livestock
production in Nigeria due to their high forage production and nutritive value (De Leeuw
and Brinckman, 1974; Olubajo, 1974). Various grass species at present exist in Nigeria
and the notable ones include Andropogon gayanus, Panicum maximum, Chloris gayana
and Sorghum almum (Agishi, 1979). The legumes, which include; Stylosanthes
guyanensis, Lablab purpureus, Stylosanthes hamata and Centrosema spp have proved
very valuable (Onifade and Agishi, 1988).
In the tropics, supply of herbage for livestock during the dry months of the year
declines substantially (Omaliko, 1983; Oloyo and IIelaboye, 2002). Enough herbage must
be produced during the production period through intensive management techniques in
order to make possible conservation for the lean season or off-season periods. Intensive
management practices include the use of fertilizers, choice of forage species, cutting
management, control of bushes and weeds and pasture establishment (Omaliko, 1983;
Dev, 2001). Attempts at enhancing the nutritive quality of the forage, particularly nitrogen
component have been through the use of nitrogen fertilizer or inclusion of legumes in
mixtures (Bamikole, 2003) The use of adapted, improved and high yielding pasture
legumes as sole crop or in mixture with grasses is one of the ways of achieving availability
of good quality forage (Omokanye, Kalla, Alawa and Otchere, 1998). It is generally
accepted that grasses normally have a competitive advantage over legumes (Wong and
Wilson, 2005); however, pasture management techniques such as fertilization and
defoliation management, are utilized in order to secure a desirable balance (Rhodes and
Stern, 1978; Keftasa, 1996).
Intensive management practices require many inputs, which are not commonly
used in natural grassland livestock production system. To be more readily adoptable and
acceptable to the resource poor farmers, the system must not be capital intensive and must
not require unduly sophisticated technology (Omaliko, 1983). The method of
establishment of a pasture should be cost effective and with minimum soil working (Dev,
2001). Some knowledge of the effects of management, such as fertilization and cutting
regimes on aspects of pasture establishment, growth and productivity could help to make
many tropical pastures more productive and efficient for animal production (Wilman,
3
Droushiotis, Koocheki, Lwoga and Shim, 1976a; Wilman, Koocheki and Lwoga, 1976b;
Wilman, Ojuederie and Asare, 1976c).
Some studies have been carried out to test the effects of cutting frequency and
initial cutting date on the production of Panicum maximum pasture sown under Nsukka
derived savanna zone of Nigeria conditions (Omaliko 1980; 1983). In those studies,
however, the effects of different nitrogen fertilizer application rates in combination with
cutting frequencies were not considered. Information is scanty on the effects of cutting
frequency and nitrogen fertilizer application on dry matter yield of Panicum maximum
sown pastures at different seasons of the year in Nigeria. There is paucity of information
on the effects of cutting frequency and fertilizer-N application on the dry matter yield and
quality of crop fractions in guinea grass (Panicum maximum) and verano stylo
(Stylosanthes hamata) mixed swards grown in Nigeria. The proportions of these crop
fractions have important bearing on digestibility (Terry and Tilley, 1964; Duru, Delprat,
Fabre and Feuillerac, 2000) and also on voluntary intake (Laredo and Minson, 1975).
Differences in habit, regrowth, and physiological growth requirements make
management of grass/legume mixtures difficult (Casler, 1988). These differences make it
difficult to maintain the proportions of each component in the grass/legume mixture. Many
recommendations for grass/legume mixtures were based on monocultures, which led to
errors in developing suitable mixtures (Casler and Walgenbach, 1990). Species that are
highly productive in monocultures are often incompatible in mixtures (Casler and
Drolsom, 1984). The influence of nitrogen fertilization is of interest, since guinea grass
has high yield potential and is responsive to nitrogen fertilization (FAO, 2003). However,
nitrogen fertilization has been found to reduce the legume content when in mixture with
grass (Guay, 2001), therefore, the influence of nitrogen application on the legume
component is of interest.
The maturity stage at cutting has been shown to be a major factor that determines
the quality of grass pastures (Keftasa, 1996). Optimum forage yields are achieved by
harvesting plants when they reach a height or growth stage corresponding to a high point
in the energy reserve cycle (Rayburn, 1993). Benefits from mixed stands of grass and
legume pastures can be efficiently exploited only if proper management strategies such as
optimum fertilization and accurate cutting frequencies are followed (Keftasa, 1996).
Some forage legumes and grasses are known to be productive and can complement
the low productivity of natural pastures in Nigeria (Njarui and Wandera, 2004). Notable
among the legumes are Stylosanthes hamata, Stylosanthes guyanensis, Centrosema
4
pascuorum and Lablab purpureus while the grasses include Chloris gayana, Panicum
maximum Sorghum almun and Andropogon gayanus. However, productivity of some of
these species has not been evaluated under varying cutting regimes in Nsukka derived
savannah area of Nigeria. There is a need to develop an appropriate management
harvesting strategy for these pasture species to maximize dry matter production.
Objectives
The objectives of the present research therefore are:
1. to study the effects of fertilizer N and cutting management on the establishment,
growth and yield of guinea grass (Panicum maximum) or guinea grass-verano stylo
mixed swards.
2. to evolve the best combination of fertilizer-N rate and cutting management for
optimization of herbage dry matter yield and herbage quality in guinea grass or
guinea grass-verano stylo mixed swards.
3. to investigate the effect of different cutting regimes on herbage dry matter
production of four sown grasses and four legumes under Nsukka ecological
conditions.
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