Continuous supply of adequate and nutritious green forage is essential for
the promotion and development of livestock, which plays a significant role in
the economy of Pakistan. Livestock sector accounts for 38% of the agricultural
value added and about 10% of total G.D.P. (Anonymous, 1997).
Green forage not only meets the fodder requirement but also minimizes the cost of feeding. Though in Pakistan, it is available during most port of the year, yet it is difficult to maintain its regular supply. Due to scarcity of green fodder in May-June and October-November, the animals are subjected to low productivity, which in turn, results in heavy monetary losses to the owners of livestock. Against the estimated requirement of 358.11 million tones, only 165.76 million tones of green forage is available for livestock in Pakistan, which presents 53.71% forage deficiency (Anonymous, 1998).
In Pakistan, about 16 per cent of the total cropped area is put under forage crops annually, even then regular supply of adequate and quality forage is not being ensured (Hanjra et al., 1995). The present trend to bring more of the cultivated area under cash crops at the expense of forage crops may further deteriorate the green forage supply to livestock.
Shortage of green forage can be alleviated either by shifting growing seasons of the conventional forage crops or by the introduction of high yielding new multicut forages which can supply green herbage in adequate quantities during the scarcity periods (Ahmad et al., 1993). Recently a number of high yielding forage crop varieties have been introduced in Pakistan and Mott elephantgrass (Pennisetum purpursum Schum) is one of the promising forages, which have the potential to meet the challenges, at it not only provides more herbage per unit area but also ensures regular green forages supply due to its multicast nature.
Since the grass is heterozygous and does not breed true from seed, it must be propagated vegetatively to obtain true to type population (Hanna and Monson, 1988), using stem cuttings or root stocks. It is best adopted to moderately well drained soils. Cold tolerance is comparable to that observed for Merkeron, one of the most cold tolerant elephantgrass cultivars.
Mott grass was introduced to Pakistan in 1988. Although some of the farmers have started its cultivation yet its success will depend upon the evolution of a comprehensive package of agro-technology compatible with the local agro-climatic conditions. One vital component of agro-technology for Mott grass is proper plant spacing which play a key role in the development of quick growing grasses like Mott that tillers profusely (Bilal et al., 2000).
The row spacing chosen may depend on the intended use for the crop stand. Plant spacings of 24 to 30 inches in the row results in a full stand of Mott elephantgrass by early summer of the year after planting (Woodard et al., 1985). Increasing plant density compensates, at least partially, for stems of low propagation quality (Sollenberger et al., 1990). Close spacings gives significantly higher forage productivity than wide plant spacing at least during the first year of plant stand establishment of Mott grass (Saeed et al., 1996).
Materials and Methods
A field experiment was conducted on Mott grass at the Research Area of Agronomy,
Forage Production Section, Ayub Agricultural Research Institute, Faisalabad.
Soil samples were analysed for physical and chemical properties. A randomized
complete block design (RCBD) was used. The experiment was replicated four times.
Net plot size was 2.7x13 m, 3.6 m x 13 m, 4.5x13 m, 6.3x13 m and 7.2x13 m for
plant spacings S1 = 45x45 cm, S2 = 60 x 60 cm, S3=75x75
cm, S4=90x90 cm, S5=105x105 cm and S6=120x120
cm, respectively. In each plot there were 6 rows of the crop. Mott elephantgrass
was planted manually in the 2nd week of March on a well prepared seed bed as
per spacing treatments using root stock of uniform size. The crop was fertilized
@ 100 kg N2 and 100 kg P2O5 ha-1.
All of the phosphorus and half of N2 were applied at the time of
planting as a basal dose. while the remaining half of N2 was applied
five weeks after planting. Whereas in subsequent two cuttings the full dose
of N2 was applied in two equal splits each at the time of 1st irrigation
after cutting and five weeks after the 1st application. All other agronomic
practices were kept uniform and normal for all the treatments.
The height of the five randomly selected plants from each plot was measured with a meter and from the base of a plant to its highest growing point at harvest and averaged thereafter. At harvest, number of tillers of five randomly selected and tagged plants in each plot was counted and averaged.
Fresh weight stored was determined by weighing five randomly selected plants from each plot at harvest an a spring balance and averaged. For determining forage yield at harvest, all the plants were cut at an appropriate stubble height and weighed with the help of spring balance. Thereafter the green forage yield per plot (kg) was converted into tones ha-1.
The dried and ground samples were preserved in labeled air tight containers for analysis of various components such as Fat contents, crude protein content and in vitro dry matter digestibility.
The data collected on various parameters were tabulated and subjected to statistical analysis by using Fishers analysis of variance technique and the treatment means were compared by using least significant difference (LSD) test at 0.05 % level of significance (Steel and Torrie, 1984).
Results and Discussion
Plant height Plant-1
Plant height is an important yield contributing parameter in forage
crops. The data in plant height indicated that different spatial arrangements
affected the plant height significantly. In three cuttings, the crop planted
at 45x45, 60x60 and 75x75 cm although produced at 105x105 and 120x120 cm but
were at a par with 90x90 cm spacing pattern. However, the minimum plant height
in all the three cuttings were recorded in the planting pattern of 120x120 cm.
The more plant height recorded in narrow spacings might partly be attributed
to more plants to develop tendency to get increased internodal distance. Similar
results were reported by Scurtu (1982) who noted that increasing plant population
of maize from 40, 000 to 90, 000 plants ha-1 increased plant height
from 196 to 215 cm. Nazir et al. (1997) also reported that plant height
of multicut hybrid sorghum decreased progressively with an increase in plant
Number of tillers stool-1 at harvest
Plant density per unit area at harvest is the major yield component in forage
crops. It is evident from data that there were significant differences among
the spacing patterns in all the three cuttings. In three cuttings, the number
of tillers stool-1 although increased in a linear fashion with an
increase in the size of spacing area from 45x45 cm to 120x120 cm, but the difference
between each of 45x45, 60x60, 75x75, 90x90 cm and that of 105x105 cm and 120x120
cm spacing treatments was non-significant. However, the maximum tillers were
recorded in a spacing pattern of 120x120 cm followed by 105x105 cm against the
minimum of 11.50 tillers stool-1 in a spacing pattern of 45x45 cm.
Significant variation among the different spacing patterns was ascribed to their
variable nutritional area and ecosystem. In general number of tillers stool-1
increased progressively with an increase in the size of spacing. These findings
are in agreement with those of Khan and Manghatt (1965) who reported that Bajra
Napiergrass produced a greater number of tillers stool-1 at wider
row spacing. Similar Siddiqui (1994) also reported that number of tillers stool-1
in Mott grass increased consistently with an increase in plant spacing.
Fresh weight stool-1
Fresh weight stool-1 was affected significantly by different spatial
arrangements in all the three cuttings. The crop planted at 120x120 cm produced
significantly the highest fresh weight stool-1 followed by 105x105
cm spacing which differed significantly from rest of the spacing treatments.
The minimum fresh weight stool-1 was recorded in the spacing pattern
of 45x45 cm which amounted to be 2.44 kg stool-1, respectively against
significantly the maximum of 5.17 kg stool-1 respectively (Table
1). However, the data in fresh weight stool-1 revealed that there
was a linear increase in fresh weight stool-1 with an increase in
spacing size from 45x45 cm to 120x120 cm. Similar results were reported by Patil
and Jawala (1977). Who reported that there was a progressive increase in fresh
weight plant-1 of sorghum (Sorghum vulgare) with increase
in plant spacing.
Siddiqui (1994) also reported that fresh weight stool-1 of Mott grass increased with the increase in plant spacing.
Forage yield (t ha-1)
There was a significant variation in forage yield among the different spatial
arrangements. The crop planted in the pattern of 45x45 cm yielded significantly
higher than all other treatments. There was a consistent decrease in forage
yield with an increase in the size of spacing from 45x45 cm to 120x120 cm in
all the three cuttings. The total forage yield of 387.0 t ha-1 for
the three cuttings was recorded at 45x45 cm against the minimum yield of 100.19
t ha-1 at 120x120 cm spacing.
||Ave. Plant height, number of tillers stool-1, fresh
weight stool-1, fat contents, protein % and digestibility % in
leaves and stem as affected by different spatial arrangements
The highest forage yield at 45x45 cm was attributed to more number of stools
unit-1 area which ultimately contributed to increased forage yield
as compared to wider spacing. These results are in line with those of Khan and
Manghatt (1965), Siddiqui (1994) and Saeed et al. (1996), who reported
that green fodder yield of Mott grass decreased as plant spacing was increased.
These results further indicated that favorable effect of wider spacing on fresh
weight stool-1 did not compensate the yield reduction caused by less
number of stools at wider spacing.
Fat contents in leaf and stem
Fat content in leaves as well as in stem varied significantly among the
different spatial arrangements. The crop planted in the pattern of 45x45 cm
being at par with that of 60x60 cm accumulated significantly higher fat content
in leaves than at rest of the spacing patterns. The differences among 90x90,
105x105 and 120x120 cm spacing patterns were also non-significant showing a
range of 2.03 to 2.15% fat content in leaf (Table 1).
Similarly fat content in stem was recorded significantly the highest in the crop spaced at 45x45 cm which was on a par at 120x120 cm spacing which was at par with that recorded at 105x105 cm or 90x90 cm spacing pattern. Overall, the maximum fat content in plant (leaves & stem) was recorded at narrow spacing of 45x45 cm against the minimum for the crop spaced at 120x120 cm. In general it was observed that the maximum value for ether extract was recorded in leaf fraction and minimum was found in case of stem fraction. These results are in line with those of Gennari and De-Mattos (1977).
Protein content (%)
There was a significant variation among the different spacing treatments
with regards to protein content in leaves and stem. Significantly the highest
protein content in leaves was recorded in the crop spaced at 45x45 cm against
the lowest of 11.50% at 120x120 cm spacing which was at par with that spaced
at 105x105 cm or 90x90 cm spacing pattern. Similarly the difference between
75x75 cm and 60x60 cm spacing pattern was non-significant. The higher protein
content in leaves at 45x45 cm might be attributed to narrow spacing as a result
of which plant absorbed more nitrogen from the soil as compared to wider spacing.
It was also due to higher Net assimilation rate at 45x45 cm spacing which resulted
in higher protein content.
Similarly protein content in the stem varied significantly among the spacing patterns. Statistically the less protein contents were recorded at 120x120 cm, 105x105 and 90x90 cm spacings with a range of 6.55 to 7.05% which was significantly lower than that recorded at 75x75, 60x60 and 45x45 cm spacing which in turn were at par with one another showing a range of 7.78 to 8.18%. However, the maximum protein content in stem was recorded at 45x45 cm closely followed by 60x60 against the minimum 6.55% at 120x120 cm spacing patterns. These findings are in contrary with those of Singh et al. (1985) who reported that CP content was the highest (21.0%) in the blue panic grass (Panicum antidotale) at the widest row spacing. Gupta et al. (1976) Gupta and Sagar also reported that leaf has more crude protein than stem.
The digestibility of leaves and stem among the different spacing treatments
differed significantly. The crop planted in the pattern of 45x45 cm although
had significantly higher digestibility percentage in leaves than rest of the
spacing treatments but was on a par with that recorded at 60x60 cm and 75x75
cm spacing patterns which showed the digestibility of 72.41 and 72.43% respectively.
The lowest digestibility percentage was recorded at 120x120 cm which was at
par with that recorded at 105x105 cm. However, the differences among 90x90,
75x75 and 60x60 cm spacing treatments were non-significant.
Similarly the highest digestibility of stem was recorded at a spacing pattern of 45x45 cm against significantly the lowest at 120x120 cm. The differences between 60x60 cm and 75x75 cm spacing patterns was also non-significant. It was observed that leaf fraction of plant had the highest digestibility whereas it was the lowest in the stem i.e., 61.16%. These results coincide with Sabitti (1985) who reported that mean; In vitro Dry matter digestibility (IVDMD) was 52% for the whole plant, 56.2% for leaves and 43.3% for stem indigofera.
Wilson et al. (1989) also reported that IVDMD of buffer grass (Cenchrus cillaris) leaves ranged from 64 to 73.4% and that of stems from 47.7 to 61.7%. However, the differences in digestibility was related to morphological and anatomical characteristics of the tissues.