Wheat is one of the most demanded, valuable and strategic crop worldwide.
Apart from its use as food it has been used widely in industry especially
for alcohol production. For example, in Iran, it makes up to 66.5% of
seeds produced and meets 60-65% of required protein of the country (Amin,
1998). The planting area is about 145000 hectare with irrigation and 226000
hectare for rain-fed wheat according to the latest report (Agricultural
Jihad of Golestan Province in 2005). If it could be possible to make a
200 kg ha-1 improvement then we could make a considerable yield
increase of 75000 tones. Wheat is mostly used in supplying bread which
forms the most important food of the majority of the population of the
country. As a result of increasing population and essential needs of mankind
to this vital and strategic crop and by considering the lack of enough
resources of the production, making attempts to increase the production
per each single unit of planting area and decreasing the production costs
seem necessary. Most of the researches conducted in Iran have been in
the field of genetic issues and a few projects have been done on technical
and arable issues like cultivation density, application of tillage implements
and planting, while 60% of energy costs in agricultural practices is usually
allocated to tillage practice (Iqbal et al., 1994). Therefore,
to reach wheat production independence in Iran, conducting deeper studies
to pick out the best agricultural machines and practices that could be
used for rain-fed wheat, seem inevitable.
The purposes of tillage practices are to make an appropriate environment
for the germination of the seeds, growth of roots and for weeds control
as well as increasing the preservation of soil moisture or facilitating
the water penetration into soil. Apart from the items mentioned earlier,
soil softening and stability in order to increase seed contact with soil,
reduction of soil tolerance, cohesion and soil erosion are results of
a good tillage practice. It is important to consider moisture control,
burying vegetative remains, mixing fertilizers, pesticides and reforming
materials with soil and unsetting soil inappropriate capillaries to reduce
evaporation as other important desired consequents of good tillage programs
To achieve mentioned goals, special tillage implements could be applied
and each tillage implement has special usability and has its own advantages
and disadvantages and that`s why researchers have been trying to find
and use the appropriate ones by having the knowledge of the appropriate
purposes according to the farm situation.
In each climate and region, appropriate tillage implements should be
used concerning soil texture,precipitation, underground water depth, evaporation
amount and perspiration from soil and plant, or different tillage implements
should be compared and the most appropriate one should be determined in
Seed density (sowing rate) is an important factor on the final yield.
If it is less or more than the optimal amount, it leads to a yield reduction.
When it is more than the optimal amount, the grains become weak; consequently
fewer yields will be obtained. Among the three yield components, heads
per unit area and kernel per head considered more important than kernel
weight for determining wheat grain yield (Donaldson et al., 2001;
Shah et al., 1994; Schillinger et al., 2005). Heads per
unit area is generally the most important yield component for wheat (Garcia
del Moral et al., 2003) but under drought conditions, kernel per
head often has the greatest effect on grain yield (Arnon, 1972; Schillinger
and Young, 2004). High sowing rates often result in increased head per
unit (Guberac et al., 2000; Stougaard and Xue, 2004) with corresponding
reduction in kernel per head (Carr et al., 2003). In response to
increasing sowing rate, cereal grain yield will generally rise rapidly,
reach a broad plateau and then decline slowly (Carr et al., 2003;
The most widely recommended sowing rate for dry land spring wheat in
the northern Great Plains and the pacific North West is 200 seeds m-2
(Paulsen, 1987), but some farmers sow up to 350 seeds m-2.
Considerable variability in optimum sowing rate for cereals often involve
interactions with tillage, cultivar and environmental factors. The common
sowing rate for dry land spring cereals in the less than 300 mm annual
precipitation zone of the pacific North West is 195 seeds m-2.
Sowing rates as high as 800 seeds m-2 are reported for oat
production in Finland (Peltonensainio and Jarvinen, 1995).
So, concerning this issue and the fact that the cost of plantation rises
with increase of seed density, reaching the optimal seed density is one
of the purposes of the research.
Planting machines should also be based on the climate of each region
considering mainly soil texture and precipitation. If planting machine
doesn`t fit the regional conditions, it would lead to failures like, yield
reduction and earlier amortization of the planting machine.
One of tillage disadvantages is increasing soil compaction that leads
to a hardpan after a few years under the surface of arable soil that makes
researchers think of the possibility of reducing tillage practices because
the hardpan is not only preventing root growth deeply inside the soil
but also caused early amortization of the machinery. By reducing tillage
activities, mechanization expenditure is saved as well (Hargrave et
al., 1982). But in most of lands in Iran, plantation without tillage
practices does not have satisfactory results because soil of those regions
is too heavy (Hemat and Asadi, 1997).
In presented study the effect of different primary tillage methods (including
Moldboard Plow, Disc Plow, Chisel Plow and Offset Disc) and seed density
of Tajen wheat at the rate of 140, 150 and 160 kg ha-1 with
two planting machines (deep drill planting with press wheels and drill
planting with end wheels) on the yield of Tajen wheat cultivar was studied
in Gonbad rain-fed regions.
Touchton and Jonson (1982) conducted an experiment on the effect of 3
different methods of tillage and plantation on the yield of wheat and
soybean. The 3 tillage methods included chisel, Moldboard plow and no
tillage. The results were that the yield of soybean in the 2 mentioned
tillage methods didn`t differ, but yield of wheat in case of Plow with
Chisel Plow was less than Moldboard plow. It was indicated that when the
soil was plowed by Moldboard or Chisel Plow, before plantation, the yield
was better than no tillage.
Cox (1986) studied the effect of different methods of preparation of
soil and 2 different types of wheat seed on the amount of yield. In that
study, different methods of soil preparation included the conventional
method of the region with keeping the vegetative remains in the field
with plowing and tillage and without plowing or tillage. From the view
point of the amount of yield, no significant difference was observed between
Baloch et al. (1991) conducted a farm experiment in order to compare
the yield after using implements like Moldboard, Disc, Chisel Plow and
cultivator. These experiments were conducted in two types of soil, clay-loam
and loam-silt. The results showed that Disc plow needed more pulling power
in loam-clay soil compared to loam-silt. When comparing the yield (field
capacity) cultivators had increased the yield for 48.5 and 59.1% in comparison
with Moldboard Plow and compared with Disc plow, respectively.
MATERIALS AND METHODS
Farm characteristics and the used cultivar: The experiment was
conducted in research farm of Gonbad Agricultural faculty. Average annual
precipitation is more than 450 mm. Rain fall occurs mainly during autumn,
winter and early spring. The annual average temperature of the region
was 17.7°C. According to Ambrotermic meteorology records, this region
is considered as a Mediterranean climate. Soil texture was silt-clay-loam
(64 silt, 30 clay and 6% sand) with electrical conductivity of 1.5 mμ
m-1 and the acidity of 7.8. TAGEN; A domestic high producing
rain-fed cultivar was used in this experiment.
Machinery: Two types of planting machines (deep drill with press
wheels (Hussia) with 24 cm distance of plantation lines and drill planting
with end wheels (Danish) with 12 cm distance of plantation lines) were
used. A Tractor MF 285 was used to provide pulling power as well.
The primary tillage machinery used included Moldboard Plow with 3 bottoms
mounted and one way, Disc Plow with 3 bottoms mounted, Chisel Plow with
nine tines/shanks and Offset Disc 2 way 1 angle with 18 tensile discs.
Experimental design and conducting the experiment: A factorial
split blocks experimental design was conducted in 3 replications. Factors
including (A) Planting machines in two levels (B) Primary tillage machines
in four levels and (C) seed density in three levels 140, 150 and 160 kg
ha-1 (The seed density of rain-fed wheat is currently 130-160
kg ha-1 in Gonbad region that depends on soil texture and in
soil with heavier texture, higher density is also possible because of
more preservation of rain).
The size of each main plot of the experiment for soil preparation using
each mentioned tillage machine was 72 square meters (18x4 m2,
excluding the borders). Soil moisture was about 20% based on the soil
texture at the time of plowing (tillage practice) and at the end of plowing
a tandem Disc (2 angle) was applied on the already plowed soil, so on
the whole there were 4 main plots. Then plantation with different seed
density started perpendicular to the tillage direction or to the main
plots forming subplots of 96 m2 (16x6 m) and there were 3 replications
for each treatment.
Clean, equal in size, healthy and adore less with 13-16% moisture TAJEN
wheat seeds were prepared. Purity Percentage, Germination Percentage and
weight of 1000 seeds were 100, 95% and 39 g, respectively. In order to
prevent fungal diseases, Carboxin nad Vitarax fungicides were used (150
g/100 kg seeds).
Plantation by mentioned planting machines was done considering seed rate
and planting depth of the region (2-5 times the biggest seed`s dimensions
meaning approximately 3 cm) right after soil preparation (late December
to early January) and crop protection practices including removing weeds,
preventing pests and diseases and applying chemical fertilizers were carried
out as follows: based on soil analysis, 100 kg ha-1 phosphate
fertilizer at the time of plantation and 75 kg ha-1 while digitate
in March (top-dressing fertilizer were given to the experimented plots.
After complete digitate until the growth of main stems (20-25 cm tall),
removing weeds was done using chemical poisons; 100 g ha-1
Granestar and 1 L ha-1 Pumasuper by sprayer machine. The amount
of the poison sprayed was determined based on weeds densities and the
type of the Sprayer (1-1/5 L of poison diluted with 200-400 L water ha-1).
Other special cares were done during crop protection practice including
removing yellow, black and brown blight/rust (after founding blight/rust
by spraying 2 L Zineb poison in 1000 L water). Harvest time (when crop
moisture is 14-16%, leaves are yellow and seeds are firm) was in late
spring considering high regional temperature.
Harvesting practice was carried out by a sickle under mast level, in
the middle of each plot far from the borders and the harvested crops were
put in the gunny sack labeled accordingly and transferred to Agricultural
research center of Gonbad for threshing by small combine machine. After
threshing practice (crop moisture 14%), the yield at each square meter
and finally at each hectare was calculated.
Required statistical calculations were done using statistical software
SPSS and the mean average test was performed by Donkan Multi-Amplitude
examination at p<5%.
RESULTS AND DISCUSSION
Table 1 shows a summary of the results of the variance
analysis of the average yields of rain-fed wheat. Duncan multi amplitude
test was used to carry out the comparison of the averages (Table
2). Results indicate that year and interaction effect of yearxreplication
had significant effects (p<1%) on the rain-fed wheat yield every year.
Annual precipitation in the first year of the experiment (1997-1998)
was 593.4 mm and it was 369.2 and 582.3 mm for the second and the third
And these noticeable differences in precipitation and the fact of having
rotation in the year before conducting the experiment as well as the irregular
distribution of rainfall in the third year of the experiment have led
to significant differences in terms of yield within the 3 years of conducting
||Variance analysis of different factors within 3 years of the experiment
|The type of tillage machine did not show any significant
effects on the yield (Table 1).
The data in the present study shows that when deep drill was used for
planting, in terms of yield increase Disc Plow was ranked first and Offset
Disc, Chisel Plow and Moldboard Plow were second to fourth, respectively,
so apparently Disc Plow made a better seedbed compared to other methods
resulting in a higher yield although it was not significantly different
(p = 0.46).
Although Disc Plow has made a non-significant yield increase of 5.5,
7.6 and 8.3% compared to Offset Disc, Chisel Plow and Moldboard Plow.
respectively but because Chisel Plow needs less pulling power therefore
it can be used at higher speeds and it can cover a wider area as well.
As a result, saving energy, reducing costs and required time for soil
preparation, improving physical characteristics of soil, moisture control
and preventing soil erosion are the advantages could be made by using
Chisel Plow, so based on the obtained data on this research this tillage
machine is recommended for Golestan province and similar climates and
soils for the priority of reducing tillage practices and maintaining plant
residues. Interaction effect of yearxtillage machine on the yield was
not significant (Table 1) meaning that both mentioned factors had same
effects on the yield, so it could be concluded that each year the tillage
machines have had the same effect on soil preparation and consequently
on the yield
The results obtained by French and Schultz (1984) are in line with the
findings of the resent study. Tanaka`s findings (1989) on the comparison
of the yield of pea while using different tillage treatments including
no tillage, reduced tillage and conventional tillage (Moldboard Plow)
supports the obtained results in the present study as it was indicated
in their study that the yield difference for the mentioned tillage treatments
was not significant and even no tillage showed a better yield trend. In
a study of the effect of different tillage methods on the yield of wheat,
Ciha (1982) concluded that plowing by Chisel Plow Led to a higher yield
than other tillage methods. Hodgson et al. (1989) obtained similar
However, some researchers have found significant yield increase when
applying Moldboard Plow for irrigated wheat compared to other tillage
methods (Hemat and Asadi, 1997). Afuni and Mosadeghi (2001) and Mahboubi
et al. (1993) reported that considering the fact that the type
of tillage does not have any significant effects on the yield, it`s recommended
to apply either of the two methods of soil preparation by Chisel Plow
or Disc Plow which brings along the advantages of saving required finance
and time of the soil preparation practice and reducing tillage as well,
that is in line with the results of the present research.
There were significant differences on the yield between planting machines
(p<1%) (Table 1). Comparing the average yield of each year with different
precipitation for each planting machine within the 3 years of the experiment.
Table 2 shows that deep drill planting has increased the yield on the
average 35% compared to drill planting with end wheels especially in the
first year which there was more rainfall and more appropriate soil due
to the rotation in the year before beginning of the experiment. The reasons
that led to such an increase could be explained as follows: deep drill
planting machines plant seeds deeply at the bottom of furrows providing
a good attachment to earth. This attachment especially when soil moisture
is moderate accelerates the germination of the seeds. Besides, while raining,
rain water can penetrate through furrows and consequently soil erosion
and flow of water throughout farm and organic materials wash-out could
||Comparison of the effect of the planting machines on the average
yield of rain-fed wheat in different years of the experiment with
|Values with different superscripts are significantly
different at 5% level
||Comparison of the effect of different planting machines and seed
density on the average yield of rain-fed wheat
|Values with different superscripts in two planting machines
separately are significantly different at 1% level
Apart from all the advantages mentioned, if the soil is salty, the flow
of water removes the salts away from the plants` roots piling them on narrow
heaps that improve the growth of the plants. Considering the explanation
above, it is recommended to use deep drill with press wheels in order to
plant rain-fed wheat in the studied regions.
The interaction effect of yearxplanting machine on the yield was significant
(p<1%) (Table 1). It means that the two factors of year and planting
machine didn`t have the equal effects on the yield. On the other hand,
in some years, deep drill with press wheels was better and caused a higher
yield as a result of appropriate amount and distribution of rainfalls
Seed density didn`t have a significant effect on the yield (Table 1).
The comparison of the average yield of rain-fed wheat with different seed
densities for each planting machine has shown in Table 3, as it is indicated
seed density at the rate of 140 kg ha-1 has made a non-significant
yield increase of up to 7-9% when compared with the other 2 densities.
That could be due to less competition for nutrients among seeds or enough
moisture or less plants in each plot leading to an increase in the number
of spikelets in each wheat kernel. Besides, one reason of obtaining non-significant
results could be due to the small differences among seed density treatments.
So, considering the yield increase of 7-9% although not significant,
but in order to reduce the production costs, it is recommended to reduce
seed density to 140 kg ha-1.
Khajepoor (1986) also obtained similar results and 100 kg ha-1
was recommended among seed densities of 70, 100, 150 kg ha-1,
but Saif (1976) suggested that seed density had no significant effect
on the yield. However, the seed density of 180 kg ha-1 was
recommended Table 1 shows that interaction effect of
yearxseed density; planting machinextillage machine; yearxseed densityxtillage
machine and seed densityxtillage machine; yearxplanting machinextillage
machine and seed densityxplanting machine; yearxseed densityxplanting
machine; seed densityxplanting machinextillage machine; yearxseed densityxplanting
machinextillage machine didn`t have significant effects on the yield of
rain-fed wheat meaning that all the studied factors were effective independently
or all mentioned factors in this experiment have had equal effects on
the yield of Tajen rain-fed wheat.
COMMENTS AND SUGGESTIONS
To reach more exact results it`s suggested that the following points
should be considered in similar researches:
||Difference in seed density should be chosen up to 15-20
||The farm chosen for the experiment shouldn`t be in fallow farmed
before conducting the research to reserve the nutrients for the research
plants. The rotation of crop should be considered with the current
products of the region as well.
||Soil moisture should be monitored, especially while seed formation
because the results could be more accurate.
||The depth of the hardpan layer should be measured frequently.
||Average precipitation and temperature, related to the years of conducting
the experiment should be recorded as the rain distribution is important
on the results analysis.
||Soil physical characteristics for different tillage methods should
be studied too.
||Mean Weight Diameter (MWD) of cultivar plot used in the experiment
that affects soil sustainability, before and after the tillage practice
should be measured.
||Amount of produced straw should be measured as different tillage
machines might have significant effects on the amount of straw produced.
The author would like to appreciate Dr. Biabani, Eng. Jafarzade, Dr.
Soltani, his daughter F. Shamsabadi and Mrs. A. Janati, who cooperated
with and helped him in conducting the research including soil preparation,
plantation, crop protection and harvesting also typing and aid in primary
translating into English and would like to ask God for the best of their
health while wishing them prosperity and success.