Tropical Grasslands-Forrajes Tropicales (2018) Vol. 6(1):34–41 34
Research Paper
Evaluation of growth parameters and forage yield of Sugar Graze
and Jumbo Plus sorghum hybrids under three different spacings
during the maha season in the dry zone of Sri Lanka
Efecto de distancia de siembra en el desarrollo y rendimiento de dos
híbridos de sorgo forrajero (Sugar Graze y Jumbo Plus) durante la
temporada de maha en la zona seca de Sri Lanka
HAJAROOBA GNANAGOBAL AND JEYALINGAWATHANI SINNIAH
Faculty of Agriculture, University of Jaffna, Ariviyal Nagar, Kilinochchi, Sri Lanka. www.agri.jfn.ac.lk
Abstract
A field experiment to evaluate the growth parameters and fodder yields of Sugar Graze and Jumbo Plus under occasional irrigation was conducted at 3 different plant spacings (30 × 15, 30 × 45 and 30 × 60 cm) on a red-yellow latosol in the dry zone of Sri Lanka from August 2015 to January 2016. The design was a randomized block with 3 replications. Initial harvesting of fodder was done 60 days after planting and 2 ratoon yields were assessed at successive 60-day intervals.
Plant spacing was inversely related (P<0.05) to dry matter (DM) yield with the narrowest spacing (30 × 15 cm) producing yields of 14.1 t DM/ha for Sugar Graze and 12.6 t DM/ha for Jumbo Plus at the initial harvest. Plant spacing also influenced leaf area, stem girth, root length and plant height in the initial harvest. Sugar Graze produced higher yields than Jumbo Plus at the initial and second ratoon harvests. Yields from ratoon crops were about 30% of those for the initial harvest. Further studies are needed to determine how these findings apply under the low-rainfall conditions of the yala season, and chemical analyses and animal feeding studies would provide valuable information on the nutritional value of the different forages.
Keywords: Dry matter yield, forage sorghum, ratoon crop, red yellow latosol, row width.
Resumen
En un latosol rojo-amarillo de la zona seca al norte de Sri Lanka entre agosto de 2015 y enero de 2016 se evaluaron algunas características de crecimiento y los rendimientos de forraje de los cultivares Sugar Graze y Jumbo Plus bajo riego ocasional usando 3 distancias de siembra (30 × 15, 30 × 45 y 30 × 60 cm). Los tratamientos se dispusieron en un diseño de bloque al azar con 3 repeticiones. La primera cosecha de forraje se realizó 60 días después de la siembra, seguida por 2 cosechas de rebrote a un intervalo de 60 días cada una. Los resultados mostraron que la distancia de siembra se relacionó de manera inversa (P<0.05) con el rendimiento de materia seca (MS), siendo este más alto (14.1 t MS/ha) en la distancia 30 × 15 cm en la primera cosecha para el cv. Sugar Graze en comparación con el cv. Jumbo Plus (12.6 t MS/ha). La distancia de siembra también influyó en el área foliar, el grosor del tallo, la longitud de las raíces y la altura de la planta en la primera cosecha. Sugar Graze produjo mayores rendimientos que Jumbo Plus en la primera cosecha y en la segunda cosecha de rebrote. Los rendimientos en las dos cosechas de rebrote fueron de alrededor del 30% de la primera cosecha. Se requieren estudios adicionales para determinar cómo se comparan estos resultados con los que se puedan obtener en época seca (temporada yala). Además, análisis químicos y estudios nutricionales con animales proporcionarían información valiosa sobre el valor nutritivo de los diferentes forrajes.
Palabras clave : Distancia entre surcos, latosol amarillo-rojo, rebrote, rendimiento de materia seca.
___________
Correspondence: Dr. (Ms.) Jeyalingawathani Sinniah, Department of
Animal Science, Faculty of Agriculture, University of Jaffna, Ariviyal
Nagar, Kilinochchi, 44000, Sri Lanka.
E-mail: jeyalingawathani@gmail.com
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Yield parameters of forage sorghum hybrids 35
Introduction
cultivars in the dry zone of Sri Lanka are limited. There is
a need to assess the growth of these cultivars and how
High performance of farm animals, especially dairy cows,
varying the plant spacing affects both yield and quality of
depends on the availability of adequate amounts of quality
forage so that the growing demand for forage by livestock
fodder and in developing countries, inadequacy of quality
can be met.
forage is the critical limitation to profitable animal
The present study was designed to determine the crop
production (Sarwar et al. 2002). Among the many options
morphology, growth parameters and forage yield of Sugar
for overcoming the shortage of forage, the introduction of
Graze and Jumbo Plus under irrigation in the dry zone of
high-yielding crop varieties ranks highly (Bilal et al.
Sri Lanka under 3 different plant spacings (30 × 15, 30 ×
2001). However, in many developing countries, because
45 and 30 × 60 cm).
of the ever-growing need for food for humans, only
limited cultivated land can be allocated to produce fodder
Materials and Methods
for livestock. Douglas (1980) recommended annual
summer crops such as forage sorghum hybrids ( Sorghum
This experiment was carried out at the livestock farm,
spp.) for use as alternative forage crops in drier areas in
Department of Animal Science, Faculty of Agriculture,
order to bridge the feed shortage gap.
University of Jaffna, Ariviyal Nagar, Kilinochchi (Figure
Sugar Graze, a sweet sorghum × sweet sorghum
1), from August 2015 to January 2016. These months fall
hybrid , is a popular forage source among the livestock
into Sri Lanka’s maha season, i.e. the period September –
farmers of Sri Lanka and Jumbo Plus, a sweet sorghum ×
February which experiences rainfall through the
Sudan grass hybrid, is still in the initial stages of
Northeast monsoon.
introduction. Sugar Graze is a late-flowering cultivar with
high yields, a crude protein (CP) concentration of 12‒
18% and a high sugar content that boosts feed quality and
palatability, resulting in minimal feed wastage. In
addition, the crop is resistant to a wide range of diseases.
Mature Sugar Graze promotes good weight gains and
provides adequate energy for livestock (Pacific Seeds
2009). Jumbo Plus, a forage sorghum hybrid cultivar, has
excellent re-growth potential and high productivity and is
adapted to both dryland and irrigated situations. It has
similar CP concentration to Sugar Graze with 56‒64% dry
matter (DM) digestibility when the plant is 55‒60 days
old or at 5‒10% flowering stage and can be used for
grazing, silage making and rotational cropping (Forage
These crops have the potential to compete favorably
with maize silage in terms of yield and nutritive value
(Ketterings et al. 2005) and may be an appropriate
alternative to maize for utilizing irrigation water in
drought-prone areas. The shortage of ground water is the
primary limitation to cultivating grass in the dry zone. As
such, it is essential to select a drought-tolerant grass/fodder
species, and Sri Lankan farmers cultivate fodder sorghum.
In an initial study 7 cuttings were achieved from a single
planting yielding 24 kg of fresh fodder/m2 from a single
cutting with plant spacing of 45 × 15 cm (Sivayoganathan
2016). While research on sorghum cultivars in Pakistan has
shown marked differences between cultivars in green
fodder yield and morphology under 30 cm row spacing
Figure 1. The experimental site, Kilinochchi District, in the
(Bakhsh et al. 2015), similar data on forage sorghum hybrid
dry zone of Sri Lanka.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
36 H. Gnanagobal and J. Sinniah
The remaining period of the year is dry with the driest
done at weekly intervals. Plots were manually weeded at
period being June to August. During the study period
30 days after planting to reduce competition from weeds.
(August 2015‒January 2016), rainfall in individual
Five plants were randomly selected from each plot for
months varied greatly (Figure 2) and due to the extremely
recording of leaf length and width, leaf area [leaf area
low water retention capacity irrigation had to be applied
factor (0.72 for forage sorghum) × length × width] (Arkel
in some months.
1978), number of leaves per plant, stem girth, root length
According to Vavuniya meteorological data, the
from the base of the plant to tip of the selected average
average monthly temperature in the region is 28.4 °C
lengthier rootlet, internodal elongation and plant height at
(range 25.6‒30.0 °C), while maximum and minimum
weekly intervals. At 60 days after planting, on 3 October
averages are 35.0 and 21.3 °C, respectively (Jaffna and
2015, the crops were cut 15 cm from ground level and
Kilinochchi Water Supply and Sanitation Project 2010).
allowed to ratoon. Two ratoon cuts were made at 60-day
Soils of the area are red-yellow latosols (Haplustox),
intervals, on 1 December 2015 and 29 January 2016.
which are the most intensively cultivated soils of Jaffna
Immediately after harvesting, fresh forage was weighed
Peninsula and have very low inherent fertility. Extremely
using a spring balance. Samples (approximately 2 kg) of
poor water retention properties mean that dryland cropping
the harvested forage from each experimental plot were
is inappropriate, while conventional flood irrigation is
selected and air-dried for 24 hours, followed by oven-
impractical owing to very rapid infiltration and soil drying.
drying at 75 °C for 72 h to constant weight for dry matter
The experiment was laid out in a completely
yield determination. Data were subjected to Analysis of
randomized design (CRD) in a factorial arrangement of 3
Variance and mean separation was done with Duncan’s
plant spacings (30 × 15, 30 × 45 and 30 × 60 cm) and 2
multiple range test (P≤0.05) (Duncan 1955) with SPSS
cultivars (Sugar Graze and Jumbo Plus) with 3
(Statistical Package for Social Science) version 16.0 for
replications. Sowing was on 5 August 2015.
Windows.
Results
Initial harvest
For the initial harvest the 2 cultivars generally responded
differently to variation in plant spacing in terms of plant
morphology (Table 1).
While leaf length, leaf width and leaf area were
unaffected by plant spacing for Jumbo Plus, the narrow
spacing (30 × 15 cm) produced narrower leaves with
smaller area than the medium (30 × 45 cm) and wide (30
× 60 cm) spacings for Sugar Graze. Similarly, the narrow
Figure 2. Monthly rainfall of Kilinochchi District from
and wide spacings for Jumbo Plus produced more leaves
January 2015 to February 2016. Source: Department of Census
per plant than the medium spacing, while the medium
and Statistics of Sri Lanka (2015); Kilinochchi District (2016).
spacing for Sugar Graze produced more leaves than the
narrow spacing. In general, the thickest stems were
Within rows spacing was kept constant at 30 cm and
produced at the wide spacing and the thinnest at the
the spacing between rows was varied. Seeds were sown at
narrow spacing.
the rate of 2 seeds per hill and seedlings were thinned to
A similar trend occurred with root length with longer
a single plant per hill 2 weeks after sowing resulting in
root lengths generally being associated with wide plant
plant populations of approximately 222,000, 74,000 and
spacing and shorter root lengths with narrow spacing.
55,000 plants/ha for inter-row spacings of 15, 45 and 60
Plant height was unaffected by spacing for Jumbo Plus,
cm, respectively. Cattle manure was applied at planting at
while the wide spacing for Sugar Graze produced the
the rate of 100 kg/ha (N: 1.2‒1.9%, P: 0.2‒0.5%, K: 0.5‒
tallest plants.
1.1%) and inorganic fertilizers were applied 1 week after
Overall, Sugar Graze displayed slightly longer, wider
establishment of plants at the rate of 50 kg urea, 25 kg
leaves with much greater area than Jumbo Plus but
triple superphosphate and 12.5 kg muriate of potash/ha.
produced fewer leaves, though differences were not
During the dry spell of the study period, irrigation was
significant. This cultivar also produced longer roots than
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Yield parameters of forage sorghum hybrids 37
Table 1. Effects of row spacing (30 x 15, 30 x 45, 30 x 60 cm) on growth parameters and yields of Sugar Graze and Jumbo Plus 60
days after planting (initial harvest).
Parameter
Sugar Graze
Jumbo Plus
30 × 15
30 × 45
30 × 60
30 × 15
30 × 45
30 × 60
Leaf length (cm)
90.6 ± 4.92a
91.4 ± 2.17a
92.8 ± 2.69a
86.5 ± 3.52a
89.5 ± 2.19a
87.6 ± 3.11a
Leaf width (cm)
8.6 ± 0.86b
9.2 ± 0.80a
9.2 ± 0.67a
7.27 ± 0.64a
7.37 ± 0.83a
7.15 ± 0.91a
Leaf area (cm2)
560 ± 64.5b
608 ± 61.1a
616 ± 48.8a
443 ± 36.6a
463 ± 66.7a
473 ± 67.9a
Number of leaves/plant
13.0 ± 0.93b
13.9 ± 0.83a
13.3 ± 0.96ab
15.0 ± 0.93a
13.7 ± 0.90b
15.1 ± 1.68a
Stem girth (cm)
5.50 ± 0.38b
6.23 ± 0.86a
6.65 ± 0.62a
5.65 ± 0.52b
6.03± 0.77b
6.57 ± 0.46a
Root length (cm)
23.5 ± 0.01c
28.3 ± 0.01a
26.0 ± 0.01b
22.3 ± 0.01c
24.3 ± 0.01b
25.6 ± 0.01a
Internodal elongation (cm)
21.9 ± 2.54a
20.6 ± 1.95a
21.4 ± 2.41a
20.8 ± 1.77a
22.7 ± 1.16a
23.2 ± 1.95a
Plant height (cm)
227 ± 22.7b
239 ± 40.6b
278 ± 18.5a
290 ± 14.8a
292 ± 14.3a
297 ± 25.4a
Dry matter yield (t/ha)
14.1 ± 2.60a
11.4 ± 1.94b
11.3 ± 1.80b
12.6 ± 2.77a
9.2 ± 2.81ab
6.3 ± 1.71b
Each value is a mean ± SD for 3 replicates.
Within rows and cultivars, means without a common letter differ (P≤0.05).
Jumbo Plus but internodal elongation was greater for
Dry matter yields followed similar trends in both
Jumbo Plus, resulting in taller plants.
cultivars with declining yields as plant spacing increased,
Dry matter (DM) yields were inversely related to plant
but differences were not always significant (Table 2).
spacing with yield decreasing progressively as plant
Varietal differences in DM yield were small.
spacing increased, although differences were not always
significant. Sugar Graze produced higher DM yields than
Second ratoon crop
Jumbo Plus (Table 1).
As for the first ratoon crop, row spacing had no significant
First ratoon crop
effect on leaf width, leaf area and stem girth in either
cultivar, while inconsistent responses occurred for the
In the first ratoon crop some parameters, viz. leaf length,
remaining morphological parameters (Table 3). There were
number of leaves and plant height, were not influenced by
consistent effects of row spacing on DM yields in both
spacing in either cultivar, while leaf width, leaf area,
cultivars with yields declining as plant spacing increased,
internodal elongation and stem girth varied inconsistently
but differences were significant (P<0.05) only for Jumbo
with row spacing in the 2 cultivars (Table 2). Varietal
Plus. Dry matter yields for Jumbo Plus at the medium and
differences also were noted among the morphological
wide spacings declined dramatically to about half those for
parameters of the first ratoon crop, where generally leaf length
Sugar Graze. Overall, increases in row spacing resulted in
and width, leaf area, number of leaves per plant and stem girth
greater percentage yield decreases in Jumbo Plus than in
were greater for Sugar Graze, while Jumbo Plus showed
Sugar Graze. Yields for both ratoon crops were generally
higher values for internodal elongation and plant height.
about 25‒35% of those obtained at the initial harvest.
Table 2. Effects of row spacing (30 x 15, 30 x 45, 30 x 60 cm) on growth parameters and yields of first ratoon crop of Sugar Graze and Jumbo Plus.
Parameter
Sugar Graze
Jumbo Plus
30 × 15
30 × 45
30 × 60
30 × 15
30 × 45
30 × 60
Leaf length (cm)
78.3 ± 5.07a
72.7 ± 20.2a
78.1 ± 3.93a
71.3 ± 4.78a
71.4 ± 5.28a
70.0 ± 5.49a
Leaf width (cm)
6.79 ± 0.70a
6.01 ± 0.66b
6.37 ± 0.52ab
4.19 ± 0.41b
4.57 ± 0.34a
4.45 ± 0.49ab
Leaf area (cm2)
382 ± 50.7a
317 ± 100b
358 ± 39.1ab
215 ± 29.4a
234 ± 22.8a
224 ± 35.6a
Number of leaves/plant
9.87 ± 0.83a
9.53 ± 1.25a
10.3 ± 1.03a
9.33 ± 1.18a
9.53 ± 1.13a
8.67 ± 1.50a
Stem girth (cm)
5.15 ± 0.36a
4.45 ± 0.34b
4.63 ± 0.45b
3.83 ± 0.37a
3.88 ± 0.15a
3.63 ± 0.21b
Internodal elongation (cm)
16.1 ± 4.07a
17.8 ± 2.62a
17.5 ± 2.17a
16.9 ± 3.32b
19.6 ± 2.16a
21.1 ± 1.18a
Plant height (cm)
115 ± 19.9a
115 ± 13.0a
119 ± 14.6a
131 ± 15.8a
138 ± 11.6a
139 ± 17.4a
Dry matter yield (t/ha)
3.36 ± 0.531a 2.95 ± 0.614a 2.36 ± 0.416a 3.84 ± 0.511a 3.27 ± 0.309a 2.13 ± 0.483b
Each value is a mean ± SD for 3 replicates.
Within rows and cultivars, means without a common letter differ (P≤0.05).
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
38 H. Gnanagobal and J. Sinniah
Table 3. Effects of row spacing (30 x 15, 30 x 45, 30 x 60 cm) on growth parameters and yields of second ratoon crop of Sugar Graze and Jumbo Plus.
Parameter
Sugar Graze
Jumbo Plus
30 × 15
30 × 45
30 × 60
30 × 15
30 × 45
30 × 60
Leaf length (cm)
62.7 ± 6.15a
59.0 ± 3.58a
57.5 ± 13.1a
60.7 ± 5.57a
51.5 ± 7.15b
54.5 ± 4.63ab
Leaf width (cm)
5.78 ± 0.78a
5.73 ± 0.82a
5.65 ± 0.98a
3.63 ± 0.47a
3.68 ± 0.62a
4.13 ± 0.38a
Leaf area (cm2)
262 ± 50.7a
244 ± 45.4a
239 ± 89.0a
158 ± 18.5a
137 ± 35.0a
162 ± 21.7a
Number of leaves/plant
7.00 ± 0.63b
7.00 ± 0.01b
8.33 ± 0.52a
6.00 ± 0.63a
6.00 ± 0.63a
6.66 ± 0.82a
Stem girth (cm)
4.50 ± 0.55a
4.25 ± 0.42a
4.08 ± 0.38a
3.17 ± 0.26a
3.20 ± 0.32a
3.36 ± 0.22a
Internodal elongation (cm)
20.0 ± 2.83a
22.1 ± 2.13a
19.0 ± 1.95b
25.2 ± 3.95a
26.7 ± 3.36a
24.4 ± 2.48a
Plant height (cm)
190 ± 17.2a
178 ± 10.2ab
167 ± 10.1b
191 ± 9.12a
182 ± 8.91a
168 ± 9.31b
Dry matter yield (t/ha)
4.47± 0.744a 3.29 ± 1.090a 2.85 ± 0.350a 4.33 ± 0.358a 1.77 ± 0.206b 1.42 ± 0.539b
Each value is a mean ± SD for 3 replicates.
Within rows and cultivars, means without a common letter differ (P≤0.05).
Discussion
(460 ± 58.9 cm2) may be due to differences in genetic
makeup of the cultivars. Musa et al. (1993), Naeem et al.
Leaf length and width
(2002), Mahmud et al. (2003) and Chohan et al. (2003;
2006) also observed variation in leaf area among various
Leaf development has been described extensively for
cultivars and varieties of forage sorghum.
fodders, as growth is mostly reflected in large increases in
leaf length as plants grow to maturity, accompanied by
Number of leaves per plant
relatively small increases in width and thickness (Skinner
and Nelson 1994). Large leaf lengths are also important
The general absence of any consistent effect of row spacing
for the survival of individual plants within a sward (Barre
on leaf number per plant is in agreement with the findings
et al. 2015). Leaf length and width values observed for
of Liu et al. (2004), who observed for maize that it did not
both cultivars during the present study were slightly
affect leaf number. In contrast Lamana (2007) reported that
greater than the values recorded by Singh et al. (2014) for
wider plant spacing in maize had a positive effect on
leaf length (45‒70 cm) and width (4‒7 cm) of sorghum
number of leaves. The values recorded for number of
hybrids. Leaf length of Sugar Graze was similar to the 95
leaves per plant for both cultivars in the present study were
± 2.0 cm reported by Pahuja et al. (2014) in India, for the
consistent with those of Monteiro et al. (2012), who
first cut at 50% flowering and a spacing of 15 × 45 cm,
reported that number of leaves in forage sorghum is
whereas leaf width was slightly higher than that recorded
generally between 14 and 17. Chohan et al. (2003) and
by the same authors (6 ± 0.58 cm).
Naeem et al. (2002) also reported variation among different
cultivars of sorghum for number of leaves per plant.
Leaf area
Stem girth
The results of the present study demonstrate that leaf area
increases as plant spacing increases as shown by Lamana
Stem girth recorded in the present study was similar to
(2007). This could be due to less competition among
that reported by Pahuja et al. (2014) in India for stem girth
plants for space and soil nutrients as the plant population
of Sugar Graze (5.9 ± 0.21 cm at 50% flowering stage and
per unit area decreased. Therefore, the lower population
15 × 45 cm spacing). While Yosef et al. (2009) and Ayub
density which resulted from the wider plant spacing gives
et al. (1999) found significant variation in stem diameter
better conditions for more accumulation of photosynthetic
among different cultivars of sorghum, cultivar differences
products, better growth and expansion of foliage, which
in our study were not statistically significant (P>0.05).
was in turn expressed in greater DM yields. The range of
values for leaf area (440‒615 cm2) for Sugar Graze and
Root length
Jumbo Plus in the present study were in agreement with
the values reported by Nabi et al. (2006) for advanced
The trend for root length to increase as row spacing
lines of forage sorghum cultivars. The higher mean leaf
increased would reflect greater competition between
area in Sugar Graze (595 ± 62.3 cm2) than in Jumbo Plus
plants at the narrower spacings. Despite the shorter root
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Yield parameters of forage sorghum hybrids 39
length per plant at the narrow spacing, the much greater
cultivars. Epasinghe et al . (2012) reported DM yields of
plant populations at this spacing would have resulted in
Sugar Graze in Sri Lanka of 5,230 kg/ha at 60 days after
substantially greater root length per unit area than at the
planting at 45 × 15 cm spacing and these lower yields
wider spacings. As a result plants at the narrow spacing
might be attributed to the differences in the spacing, soil
would have had better opportunity to utilize soil water and
fertility and environmental conditions. By contrast Nabi
nutrients than at wider spacing, resulting in higher DM
et al. (2006) recorded yields of 10,400‒13,100 kg DM/ha
yields.
for advanced lines of forage sorghums and Silungwe
(2011) recorded 13,262 kg DM/ha at 15 cm row spacing
Internodal elongation and plant height
78 days after sowing for Sugar Graze.
Forage yield is a function of growth parameters, viz.
Plant height as a growth parameter is a result of elongation
plant population, plant height, leaf:stem ratio, leaf area,
of the stem internodes, which is influenced by the
and leaf area index (Lamana 2007). The differences in
environment as suggested by Weston (1967). In the current
DM yield between the 2 cultivars could be attributed to
study taller plants were observed with wider spacing,
the fact that Sugar Graze exceeded Jumbo Plus in the
which contrasts with reports in the literature that narrower
growth parameters leaf length and width, leaf area and
spacing will give taller plants as a result of competition for
root length. Watson (1947) has shown that variation in
sunlight (Lamana 2007). However, the absence of any
total dry weight of plants is more dependent on variation
effect of plant spacing on plant height of Jumbo Plus
in leaf area. Light interception capacity of the leaf is
supports the finding of Roy and Biswas (1992) that plant
amplified with the increase in leaf area often leading to
height at maturity was not affected by plant spacing. The
increase in photosynthesis and DM yield. Therefore,
significant differences in plant height between the 2
higher DM yield recorded for Sugar Graze might be
cultivars may be due to genotypic variation, as differences
attributed to its higher leaf area than Jumbo Plus.
in internodal elongation between varieties can lead to
differences in height as reported by Evans (1975) and
First and second ratoon crops
Weston (1967). Nabi et al. (2006) and Silungwe (2011),
who worked with different forage sorghum cultivars, also
The most consistent findings with the ratoon crops were
reported plant heights (203‒230 cm) lower than those in
that there were fewer leaves per plant, leaves were
the present study (227‒298 cm), as did Pahuja et al. (2014)
smaller, height was less and DM yields were lower than
for Sugar Graze (189 ± 1.9 cm) in India.
for the initial harvest. However, DM yield remained a
factor of plant spacing with higher yields at narrower row
Dry matter yield
spacing, indicating that plants were still accessing
moisture and nutrients from the soil in sufficient
Plant spacing has a marked impact on the efficiency of
quantities to maintain acceptable growth levels. The
use of land, light, water and nutrients. By optimizing plant
reduced yields are possibly a function of nutrient supply
spacing, highest yield potential can be achieved from the
in the soil being depleted by the initial crop and a change
smallest possible area (Oseni and Fawusi 1986). The
in seasonal conditions over time. There were no
direct relationship between DM yield and plant
significant differences between Sugar Graze and Jumbo
population agrees with the findings of Fisher and Wilson
Plus in DM yields for the first ratoon crop, in contrast with
(1975), who reported greater DM yield with higher plant
the generally higher yields for Sugar Graze in the initial
populations than with lower plant populations. Wolf et al .
crop and second ratoon crop. Despite having smaller
(1993) and Graybill et al. (1991) also reported that DM
leaves and thinner stems than Sugar Graze, the greater
yield of forage maize responded positively to plant
height of Jumbo Plus ensured that yields in the 2 cultivars
density. This relationship would be affected by the
were similar. The success of the second crop is often a
availability of soil moisture, and the application of
function of how early the main crop was planted and
irrigation on a regular basis in this study would have
harvested, which determines the seasonal conditions
ensured that all row spacings/plant populations had
under which the first and second ratoon crops must grow.
adequate water. Dry matter yield recorded for Sugar
However, normally ratoon crops of sorghum are expected
Graze in the current study seemed to be less affected by
to yield from 25 to 35% of the main crop (Livingston and
differences in row spacing than Jumbo Plus, which
Coffman 1996), and our yields fall within this range.
appeared not to be related to root length as there were no
Significant differences in DM yield between main and
significant differences in root length between the
ratoon crops have been reported by Saberi and Aishah
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
40 H. Gnanagobal and J. Sinniah
(2014), when assessing yield responses of forage ratoon
Duncan DB. 1955. Multiple range and multiple F tests.
sorghum under varying salinity levels and irrigation
Biometrics 11:1–42. DOI: 10.2307/3001478
frequencies.
Epasinghe TM; Jayawardena VP; Premalal GGC. 2012.
Our findings suggest that both Sugar Graze and Jumbo
Comparison of growth, yield and nutritive value of maize,
multi-cut fodder sorghum and hybrid Napier (var. Co3) grown
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