Effect of Treated Municipal Wastewater on Forage Yield, Quantitative and Qualitative Properties of Sorghum (S. bicolor Speed feed)
This study was carried out to investigate the effect of treated wastewater on yield quantitative and qualitative properties in fresh forage of sorghum. The experiment was conducted at the University of Zabol in Iran during 2007 growing season by using a randomized complete block design and four replications. The treatments were managed for irrigation; with well water during entire period of growing season as control (T1); well water during entire period of growing season along with NPK (T2); wastewater during the first half of growing season (T3); wastewater during the second half of growing season (T4); wastewater and well water alternately (T5) and wastewater during entire period of growing season (T6). Results showed irrigation with wastewater lead to significant increase (p≤0.01) on total yield, leaf fresh and dry weight, stem fresh and dry weight, stem diameter and leaf number in plant based on Duncan test for comparing, maximum yield (13 ton ha-1) was obtained by irrigation with wastewater and well water alternately, also significant increase in forage qualitative indexes such as WSC, CP, ASH and significant decrease in NDF and ADF. Irrigation with wastewater and well water alternately has shown lower NDF, ADF and favorite CP in comparison with usage of wastewater during the whole growth period.
Nowadays the water crisis is one of the challenges that world is faced with.
The lack of water resources have encouraged the researchers to use of non ordinary
waters including salinity waters, municipal and industrial wastewater. By increasing
population, water consumption increases wastewater production as well. Positive
use of this new huge resource in agriculture may increase cultivate land, yield
and also may decrease the environmental pollution. As FAO has reported, application
of wastewater in agricultural context is its best applicability (Pescod,
1992). The plant suitable nutrition and using of sufficient and suitable
manure resources lead to increasing the forage quality. This rich resource from
nutrient elemental especially nitrate, moreover economic advantage because of
decrease chemical manure consume, can improve the forage quality (Shanechi,
2004; Ghanbari et al., 2007). Recently, about
300 hectares of wheat, barley, alfalfa and sorghum farms being irrigated by
treated wastewater, just around Zabol in Iran. But some deficiencies such as
weak drainage, wastewater salinity (EC>3 dS m-1), low annual rainfall
(50 mm) and very high annual evaporation (more than 4500 mm), lead to worry
in salinity, sodification and destruction of region soils (Lone
et al., 2003). One of the solutions to this problem is to irrigate
plant with wastewater and well water alternately at developed stage of growth
(Ghanbari et al., 2007). This method could be
an appropriate way to put a stop to salt accumulation and to increase the accumulated
salt leaching in soil. Generally, in attention to poor pastures of Zabol region
and high forage requirement for animal feeding, a proper choice to overcome
this deficiency is to utilize these non ordinary water resources. Irrigation
with wastewater leads to increasing in forage qualitative yield, about 3 to
3.5 times more than irrigation with well water. Also, it increased the stem
length, chlorophyll and flowering rate (Asgari et al.,
2007). Irrigating tomato with municipal treated wastewater has increased
the total fresh and dry weight of subterranean organ and upper organ in compare
with the rest treatments (Erfani et al., 2001).
Ghanbari et al. (2007) reported that irrigation
with wastewater increased the wheat yield, as well. Day
and Tucker (1977) reported that irrigation with wastewater increased the
leaf width, grain yield and postponed the sorghum maturity. Although, it had
no efficacy on protein contain but it decreased some of amino acids and plant
fiber (NDF and ADF). Marten et al. (1980) in
a research on yield of corn and canary grass have perceived that irrigation
with wastewater has significant increase on digestibility and dry matter of
corn in comparison with canary grass, although amount of protein in canary grass
is more than corn. Crude protein increase in wheat grain has been reported by
irrigation with wastewater (Ghanbari et al., 2007).
The effect of treated municipal wastewater on growth and chemical compound of
canola has no significant effects on protein and fat percentage; however the
protein percentage in the treats with low wastewater quantity and fat percentage
in the treats with high wastewater quantity were more than the rest (Kiziloglu
et al., 2007). Wastewater because of high nitrate and other nutrient
elements lead to increase the leaf to stem ratio. Eventually protein and stem
fiber percentage will increase and decrease respectively, because of enhancement
in water contains and WSC; Consequently NDF decrease in forage and silage is
resulted. It has been shown that nitrogen fertilizer lead to increase in CP,
crude fat and Ash and also decrease in celluloses, hemicelluloses, K, P, Ca,
Mg, S in grasses; in addition, little decrease in Zn, B and increases of Cu,
Co, NO3 attraction is reported (Vuckovic et
Fateh et al. (2009) in study of organic and
chemical fertilizers effects on forage yield and quality of globe artichoke
has illustrated that the fertilizers such as N, Zn, Ca and Fe increased CP,
WSC. Increase of CP, WSC and decrease of plant fiber is a result of nitrogen
fertilizer application. The present study is an investigation of treated municipal
wastewater effects on quality and quantity attributes in forage Sorghum. moreover,
acquiring the most suitable application of wastewater and well water jointly
to achieve desired qualitative and quantitative yield and to put a stop to pollution
accumulation in plant and soil is the another objective of this study.
MATERIALS AND METHODS
The study was conducted in the Agricultural Institute of Zabol University Sistan
and Baluchistan Province, Iran (30° 55 N, 61°31E). The region has
an arid climate with 483 m altitude from sea level. Annual mean precipitation
and temperature are 55 mm and 21.7°C, respectively. The soil (sandy-loam)
properties prior to the experiment are shown in Table 1.
During the 2007 growing season (120 Day), the experiment was conducted out in a randomized complete block design and four replications. The irrigation treatments were well water in all growing stages as a first treatment control (T1); well water for all growing stages along with NPK application (NPK: 100, 120, 90 kg ha-1) as a second control (T2); wastewater during the first half of growing period (The stage before flag leaf visible) (T3); wastewater during the second half of growing period (The stage after flag leaf visible) (T4); wastewater and well water alternately (T5) and wastewater during the whole growing period (T6). The chemical fertilizers, ½ N, total of P and K were applied before sorghum sowing. Each plot was constructed in 3x2.5 m with 1 m distance between plots and 2 m distances between replications. Sorghum was seeded by 25 kg ha-1, 20 cm row distance, 15 cm between plants and 3-5 cm planting depth. Seeds were planted manually using two seeds per hole in May 2007. The forage was harvested at soft dough stage of grain maturity in August 2007.
Collected data include: Yield was obtained by combining the five center
rows in 1 m2 in each plots, number of leaf, stem diameter, stem length
and fresh weight of stem and leaf were measured in 10 sample plants per plots.
The dry weight of stem and leaf were measured after drying samples at 60°c
for 48 h in an air oven (Horwitz, 2005), qualitative characteristics
are DM content (at 105°C for 24 h), residual ash (4 h at 600°C) and
OM were measured from difference of DM and Ash. One portion of these samples
was dried in an oven at 60°C for 96 h and also it ground through a 1mm sieve,
then, it was analyzed for N (Kjeldahl method; 7.021 procedure at Horwitz,
2005), content of cell wall components and content of NDF was determined
without sodium sulfite and with a heat-stable amylase (Van
soest and Wine, 1967). Acid Detergent Fiber (ADF) was determined by sequential
analysis for the residual NDF and expressed exclusive of residual Ash (Van
soest and Wine, 1967). Also WSC was analyzed by Spectrophotometer (Deriaz,
The results of analysis well water and wastewater quality are shown in Table
2 and they have been compared by suggested standards of Iran environment
conservation structure (E.C.O of Iran, 1999) and FAO water qualitative standard
has been used (Pescod, 1992).
||Soil analysis result for chemical characteristic
||Quality of well water and treated wastewater (mg L-1)
According to this standard, available water had no deficiency for irrigation
and evaluation of wastewater pollution (Table 2) showed that
magnitude of sulfate, NO3, PO4, Ca, Mg and heavy metal
concentrations were lower than critical limit (E.C.O. of Iran, 1999). For evaluation
of wastewater microbial pollution has used from determinate critical limit (E.C.O.
of Iran, 1999).
Concentration of sodium, chloride, Boron and sulfate was higher than optimum
limit which it is demonstrate the soil pollution possibility in continuously
use of wastewater. Based on FAO standards, Electrical Conductivity (EC) and
concentration of Sodium, Chloride and Boron were higher than optimum limit which
it may cause toxic outbreak in sensitive plant (Ensink et
al., 2007). Due to the high concentration of chloride, rainy irrigation
system can not be admissible. Sodium absorption ratio (SAR = 13) in wastewater
has measured to determine the existent sodium efficacy of wastewater on soil
penetration and structure. Due to low salinity (5>EC>3 dS m-1)
of wastewater the possibility of soil sodification would be low, but some long
term studies have shown that in this case also it might happen (Kiziloglu
et al., 2007).
Collected data were analyzed via SAS Institute Inc. 6.12. First of all data were analyzed by ANOVA to determine significant (p≤0.05) treatment effect. The significant difference between individual means was determined by Duncan Multiple Comparison Test.
RESULTS AND DISCUSSION
Effect of wastewater on quantitative properties
Yield: The results in Table 4 show that T5
and T6 had the highest yield, but there is no significant difference
between them. Whereas they had significant difference (p<0.05) with the rest;
Nadia (2005) have reported increase in sorghum yield
at irrigation with wastewater in whole growth period rather than well water
and it might be owing to high nitrate amount in municipal treated wastewater.
The lowest yield was belonging to T1 and T2 treatments.
As it was anticipated, the analysis of soil and water showed (Table
1, 2) that the application of NPK fertilizer in this study
have led to increase in yield. Since, applying wastewater in different amount
and times has led to significant increase in yield, so it shows that NPK application
is not the only solution to get maximum yield and there is need to apply other
macro and micro elements. It has been reported by some researchers that applying
macro and micro chemical fertilizer lead to increase in corn and sorghum yield
(Ghanbari et al., 2007).
Leaf fresh and dry weight: Leaf fresh and dry weight were significantly
affected by irrigation treatments (Table 3) the comparison
of average of fresh leaf weight showed that there is no significant difference
between T6, T5, T3 and T4, but there
is significant difference between each of them and control treatment. The lowest
fresh weight was belong to control treatment and after that T4 had
lower fresh leaf weight than the rest (Table 4). The sixth
and fifth treatments had highest dried leaf weight and T4 and T3
treatments had no significant difference and it is in accordance with other
researchers result (Ghanbari et al., 2007;
Stem fresh and dry weight: The highest fresh stem weigh was achieved
at treatments which use wastewater and there was no significant difference between
them. On the other hand, the lowest fresh stem weight was achieved at T1
and after that T2 had the lower fresh stem weight than other with
significant difference (p<0.05). Also, there was no significant difference
between T2 and T4 (Table 4) and these
results imply that irrigation with wastewater in last growth stages could not
recover the cells growth reduction and consequently plant growth and stem fresh
||ANOVA of the effect of irrigation treatments on sorghum quantitative
and qualitative yield
|ns: Non significant, **p<0.01 and *p<0.05
||Averages comparison for forage yield and other quantitative
characteristics in sorghum
|1Row means followed by the same letter are not
significantly different at 0.05 probability level
Whereas, T5 and T6 treatments led to significant enhancement
in fresh stem weight (p<0.05), applying chemical fertilizer (NPK) also have
caused to increase in fresh stem weight although it was less effective in compare
with irrigation with wastewater. The results in dry weight have followed the
fresh weight process (Table 4) and in case of increase in
stem diameter and dry stem weight of sorghum there was in accordance with results
attained by Day and Tucker (1977).
Stem diameter: The results of average comparison (Table
4) showed that wastewater treatments have statistical significant difference
(p<0.05) in comparison with control. T6 and T5 had
the most stem diameter (1.47 and 1.42 cm, respectively) than other treatments.
The lowest stem diameter was pertain to T1 (control) and T2
and in addition, no significant difference was found between T3 and
T4, therefore it could be said that stem diameter during plant growth
is affected by environmental factors. Such that, the existence of specific nitrogen
and potassium in wastewater will improve the plant growth, cell reproduction
and plant resistance (Emam, 1995) and eventually stem
diameter increases (Day and Tucker, 1977).
Leaf number in plant: The highest number of leaf was found in T5
and T6 and on the other hand the smallest number of leaf was pertained
to control treatment. Variations between T3 and T4 and
between T4 and T2 were no statistically significants (Table
3). The shortage of nutrient, inclusive of macro and micro nutrients in
control treatment may cause to decrease in plant height and number of leaf.
||Averages comparison for forage properties in sorghum
|1Row means followed by the same letter are not
significantly different at 0.01 probability level
The leaf number or leafy index is one of the important factors in forage plants.
A researcher has reported increase in leaf number by application of manure and
chemical fertilizer in sorghum (AL-Jaloud et al.,
Effect of wastewater on qualitative properties
Crude protein: Results show that there is a very significant increase (p<0.01)
in protein percentage in sorghum forage due to wastewater application (Table
3). Moreover, well vegetative growth, yield and yield components increase,
leaf number increase, specifically increase of leaf to stem ratio which is strong
evidence on presence of nitrogen in plant disposal and it is certainly due to
wastewater application such that lead to protein increase (Table
4). We should be noted that increasing of leaf to stem ratio lead to protein
increasing because of the higher leaf protein than stem (Shanechi,
The highest protein percentage was found at T6 treatment up to 26%
more that control treatment (Table 5). In fact, it was anticipated
since wastewater is full of nutrient and specifically nitrogen with basis role
on protein making in plants (Table 2) (Jacobs
et al., 1998). Several studies have shown significant increase of
crude protein in sorghum and corn by wastewater application (Mohammad
and Rusan, 2007; Ghanbari et al., 2007;
Day and Tucker, 1977). Presence of nutrient elements
in wastewater can have an important role in nitrogen uptake increase. Possibly,
existence of micro nutrients in rizospher causes to more nitrogen uptake and
eventually may enhance protein production, on the other hand some elements namely
Cu and Zn associate with protein structure and nitrogen metabolism (Jacobs
et al., 1998).
Water soluble carbohydrate: Wastewater application increased WSC in
sorghum (Table 5). The increase of structural and non-structural
carbohydrate have correlation with yield increase and high vegetative growth
(Table 4). Day and Tucker (1977) have
reported similar result about wastewater efficacy on WSC increase in sorghum.
Wastewater treatments had significant efficacy (p<0.01) on WSC in forage
sorghum (Table 5) and treatment of T6 had highest
WSC. According to inverse relationship between WSC and NDF, the decrease of
NDF due to wastewater application may increase WSC in this treatment (Smith
et al., 2002). No significant difference between T2, T3,
T4 and T5 was found in term of WSC amount but they had
increase in compare with control treatment. The lack of required nutrition for
carbohydrate production could be a reason for small amount of WSC in control
treatment (Jacobs et al., 1998; Smith
et al., 2002).
Neutral detergent fiber: Irrigation with wastewater has caused a significant
decrease (p<0.01) in NDF. Wastewater because of high nitrogen and other nutrient
has caused to increase in leaf to stem ratio and consequently, forage protein
enlargement also decrease in stem fiber because of the water content and solution
carbohydrate enlargement and eventually result in the NDF decrease on forage.
The similar result about the reduction of plant fiber in sorghum and forage
crops with wastewater application is reported by some researchers (Mohammad
Rusan, 2007; Day and Tucker, 1977). The treatment
of T1, T2 and T4 had highest NDF (46.68, 46.03,
47 and 37%, respectively), the treatment of T3, T5 and T6 had significant decrease
(p<0.01) than the rest of treatments (Table 5). It seems
that, high nitrogen percentage and potassium in wastewater which they have positive
role in nitrogen uptake and protein structure, may increase the protein and
decrease the structural carbohydrate (cellulose and hemi cellulose) in forage
sorghum. The other researchers have reported that wastewater decrease the plant
fiber percentage, as well (Tas, 2005; Smith
et al., 2002).
Acid detergent fiber: Results showed that wastewater application decreased
the ADF in the plant (Table 5). Raise in vegetative growth
specifically stem and leaf dry weight and stem diameter in result of wastewater
application may led to ADF decrease (Table 4). Vuckovic
et al. (2005) in a research have shown that application of nitrogen
fertilizers led to decrease of cellulose and hemi cellulose in pasture grasses.
Ash: The results showed that wastewater application led to significant
increase (p<0.01) in forage Ash percentage (Table 5). There
is no doubt that, existence of nutrients in wastewater has caused to vegetative
growth raise and consequently increases mineral and organic mater in plants
(Table 2 and 4). Ash enlargement at T5
and T6 demonstrate that plant have used the wastewater nutrient (Table
5). The control treatment had lowest ash percentage than other treatments.
Wastewater application has led to increase in mineral elements up to 25.2% than
control treatment. The treatment of T2 and T4 had no significant
difference in ash percentage. In fact, it was found that T4 and T2
treatments have provided the same value of nutrient for plant requirement.
Irrigation with wastewater because of high nutrient content increases the quantitative and qualitative properties in forage sorghum. Wastewater application has caused to increase in WSC, CP, Ash and also decrease in NDF and ADF which is favorite property of forage and in consequence of that the forage digestibility increase because of low cellulose and hemi cellulose. Wastewater application led to more forage quality than control and T2 treatment. Irrigation with wastewater and well water alternately (T5) and wastewater during the whole growth period (T6) had highest forage qualitative. Based on this study, for municipal wastewater application project, increasing forage quality yield, soil and environmental conservation, we recommend utilize the municipal wastewater of Zabol in the form that sorghum was irrigated with wastewater and well water alternately.
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