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The effect of traditional and reduced tillage systems on the sediment yield of plots constructed in the Mediterranean climate zone caused by natural rainfall

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The objective of this study was to investigate the effects of different types of tillage systems and different crops on the sediment yield under natural rainfalls from agricultural parcels established in two Mediterranean cities of Turkey. The study was carried out in two consecutive hydrological years, in which both total precipitation and precipitation pattern were different. The results indicated that the soil tillage system (P ≤ 0.05) and whether or not the plant production was implemented in the parcels (P ≤ 0.01) had statistically significant effect on the sediment yield of the parcels. Although the total sediment yield was not statistically different for both hydrological years, there was a statistical difference between two years in terms of sediment yield per unit rainfall (P ≤ 0.01). The applied tillage system and the rainfall pattern are considerably effective on the erosion.
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I
nt. J. Global Warming, Vol. 21, No. 4, 2020 393
Copyright © 2020 Inderscience Enterprises Ltd.
The effect of traditional and reduced tillage systems
on the sediment yield of plots constructed in the
Mediterranean climate zone caused by natural rainfall
Tugrul Yakupoglu*
Department of Soil Science and Plant Nutrition,
Faculty of Agriculture,
Yozgat Bozok University,
Yozgat, Turkey
Fax: 0090-3542421096
Email: tugrul.yakupoglu@bozok.edu.tr
*Corresponding author
Turgay Dindaroglu
Department of Forest Engineering,
Faculty of Forestry,
Kahramanmaras Sutcu Imam University,
Kahramanmaras, Turkey
Email: turgaydindaroglu@hotmail.com
Abdullah Emin Akay
Department of Forest Engineering,
Faculty of Forestry,
Bursa Technical University,
Bursa, Turkey
Email: abdullah.akay@btu.edu.tr
Kadir Kusvuran
Alata Horticultural Research Institute,
Republic of Turkey Ministry of Agriculture and Forestry,
Mersin, Turkey
Email: kusvuran@hotmail.com
Veysel Alma
Department of Soil Science and Plant Nutrition,
Faculty of Agriculture,
Kahramanmaras Sutcu Imam University,
Kahramanmaras, Turkey
Email: veyselalma46@gmail.com
394 T. Yakupoglu et al.
Recep Gundogan
Department of Soil Science and Plant Nutrition,
Faculty of Agriculture,
Harran University,
Sanliurfa, Turkey
Email: recepgundogan60@gmail.com
Abstract: The objective of this study was to investigate the effects of different
types of tillage systems and different crops on the sediment yield under natural
rainfalls from agricultural parcels established in two Mediterranean cities of
Turkey. The study was carried out in two consecutive hydrological years, in
which both total precipitation and precipitation pattern were different. The
results indicated that the soil tillage system (P 0.05) and whether or not the
plant production was implemented in the parcels (P 0.01) had statistically
significant effect on the sediment yield of the parcels. Although the total
sediment yield was not statistically different for both hydrological years, there
was a statistical difference between two years in terms of sediment yield per
unit rainfall (P 0.01). The applied tillage system and the rainfall pattern are
considerably effective on the erosion.
Keywords: fallow; rainfall; sainfoin; sediment; tillage; wheat.
Reference to this paper should be made as follows: Yakupoglu, T.,
Dindaroglu, T., Akay, A.E., Kusvuran, K., Alma, V. and Gundogan, R. (2020)
‘The effect of traditional and reduced tillage systems on the sediment yield of
plots constructed in the Mediterranean climate zone caused by natural rainfall’,
Int. J. Global Warming, Vol. 21, No. 4, pp.393–406.
Biographical notes: Tugrul Yakupoglu received his PhD degree from
Ondokuz Mayis University, Turkey. He took the title of Associate Professor
with studies on soil and water conservation. He maintained his work around a
sustainable ecology because he believed that crop quality is closely related to
the healthy environment. He is currently the Head of Soil Science and Plant
Nutrition Department. He has supported many prestigious international
scientific meetings as a member of the organising committee, scientific
committee and participant. He is currently a member of Management
Committee (MC member) in the EU COST action FIRElinks.
Turgay Dindaroglu is an Associate Professor of Forest Engineering Department
at the Kahramanmaras Sutcu Imam University. He graduated with Bachelor of
Science in Forest Engineering Department from Karadeniz Technical
University in 2000. He received his Doctorate in Soil Science and Plant
Nutrition from Ataturk University. He is involved in intensive teaching and
research activities. His research interests include the soil ecology, erosion, land
degradation, karst ecosystems, soil organic carbon, etc.
Abdullah Emin Akay is a Professor in Forest Engineering Department. He
received his PhD degree from Oregon State University. His thesis was on
designing low-volume roads with reduced sediment yield and minimum cost.
He has published many research articles and conference papers on the subject
of terramechanics and sediment prediction models.
Kadir Kusvuran received his MSc degree from Cukurova University in Turkey.
He is a researcher in Republic of Turkey, Ministry of Agriculture and Forestry,
Alata Horticultural Research Institute. He is working on catchment
management and hydrology.
The effect of traditional and reduced tillage systems 395
Veysel Alma received his MSc degree. His thesis topic was gully erosion
monitoring by unmanned aerial vehicles. Water erosion is the focus of his
work.
Recep Gundogan graduated with a Bachelor of Science in Soil Science from
the University of Cukurova. He continued his education when he completed his
Master’s in Soil Science from the University of Cukurova. In 1993, he
completed his PhD work in Soil Genesis, Classification and Mineralogy from
Cukurova University. He joined the Agricultural Faculty at Harran University.
His research involves pedology, soil quality, land degradation and salinity. His
current research mainly focuses on understanding the causes of decline in soil
quality to develop solutions to land degradation.
1 Introduction
Today, the world is experiencing a global change. The most obvious reflection of this
change is the climate change which dramatically affects the natural resources. Since
natural resources are indispensable world heritages for the sustainability of life, the
impact of climate change on them reflects particularly the environmental policies, food
policies and agricultural policies. Therefore, the preferential mission of soil scientists
should be conducting climate change centred studies to predict how climate change can
lead to alterations in ecosystem functions (Janzen et al., 2011).
Mediterranean climate zone is one of the regions that will be most affected by
climate change. Land degradation and soil erosion are the most important environmental
problems in the Mediterranean region due to both strong seasonality of hydrological
regimes and long-term human effects (Barreiro-Lostres et al., 2017). In a study conducted
in semi-arid climate region of southeastern Spain, Martinez-Mena et al. (2001) has
reached the conclusion that rainfall of more than 15 mm h–1 intensity rainfall need to be
considered as erosive rainfall, considering the total soil loss and the carrying capacity of
the resulting surface flow. The way to overcome soil loss problems is to enhance and
improve the soil structure. The vegetation cover plays a key role in soil erosion by
improving the soil quality with the contribution of organic matter provided into the
system. It has been revealed by many studies that soil structure shows different
development under the different types of vegetation in the Mediterranean climate zone
(Martinez et al., 2008; Celik et al., 2012).
It is known that soil, which is the main component of terrestrial ecosystem, plays a
very important role in ecosystem functions (Adhikari and Hartemink, 2016). Accurately
planned land management practices are very effective in mitigating the negative impacts
of climate change on agriculture. However, this issue has to be dealt with in many
different aspects such as tillage, irrigation, drainage, plant pattern, rainfall pattern of the
region, and socio-economic and cultural conditions of people living in that region in
order to maintain and improve the quality of the soil (Follet, 2010). For these reasons,
the way to minimise the negative impacts of climate change on agriculture in the
Mediterranean region is not only to change the type of plant produced in the field, but
also to determine the right tillage systems. Rodrigo-Comino et al. (2017) reported that
one of the main reasons for the excessive soil and water losses in the Spanish vineyards
in the semi-arid climate region is the intensive soil tillage.
396 T. Yakupoglu et al.
Reduced soil tillage systems have been developed to overcome the negative effects of
conventional tillage systems. Traditional tillage (TT) is a tillage system using cultivation
as the major means of seedbed preparation and weed control. Typically includes a
sequence of soil tillage, such as ploughing and harrowing, to produce a fine seedbed, and
also the removal of most of the plant residue from the previous crop (OECD, 2001a).
Conservation tillage including reduced tillage (RT) is a tillage system that creates a
suitable soil environment for growing a crop and that conserves soil, water and energy
resources mainly through the reduction in the intensity of tillage, and retention of plant
residues (OECD, 2001b).
TT systems cause excessive sediment to be transported by rainfall. Besides, these
systems have serious negative impacts on the quality indicators of soils in the semi-arid
Mediterranean regions where degradation of soil ecosystems can reach serious
dimensions (Acar et al., 2018). However, conservation tillage systems increase the
macro-aggregate development and decrease soil erosion due to their contributions to
carbon sequestration (Shu et al., 2015).
In a study conducted in South Brazil, it was found that the soil transported from the
unit area of a basin with heavy tillage is almost twice that of the basin with no tillage, and
the runoff coefficient of the basin with heavy tillage was found to be 31% while it was
14% in the basin with no tillage (Didone et al., 2014).
In the light of the information provided by the literature listed above, the crops which
can contribute to the increase of organic matter in the soil should be included in the
production pattern and the reduced soil tillage systems should be implemented in order to
reduce the sediment formation and transportation from agricultural lands. On the other
hand, depending on the soil characteristics, the effects of the management systems and
the selected crops on sediment yield will be different in the agricultural lands located in
the Mediterranean region, which is highly affected by climate change. Although the
cultivation of wheat and sainfoin is very important in Turkey, the studies of the
protection of cultivated land where these plants are limited and there are many issues
could not be clarified. This study aimed to investigate the effects of traditional and RT
systems on the sediment yield from the agricultural parcels (fallow, wheat and sainfoin)
under natural rainfalls in the Mediterranean climate zone.
2 Material and methods
2.1 Study area
The study area was located in a Mediterranean city of Tarsus (Mersin) in Turkey. The
sample parcels were established on the land of ‘Topcu Research Station’ of ‘Alata
Horticultural Research Institute’ under ‘General Directorate of Agricultural Research and
Policies’ connected to the ‘Ministry of Agriculture and Forestry’. The approximate
coordinates of the terrain where the experiment was established are 37°01’51.33”N
(latitude) and 35°01’28.24”E (longitude) and its elevation is 81 m above sea level.
According to the assessment of the Mediterranean climate for many years (1929–2017),
the annual total precipitation is 700 mm and the average annual temperature is 19.1°C
(Climate-data, 2018; TSMS, 2018). The climate type in the study area can be called as
Csa according to the Köppen-Geiger classification (Ozturk et al., 2017). The annual
The effect of traditional and reduced tillage systems 397
RUSLE-R value of falling rainfall (2005–2014) is 1,490.26 MJ mm ha–1 h yr–1 (GDCDE,
2016). Soil where the experiment was established is classified as Typic Xerochrepts (Soil
Survey Staff, 2014). Its textural class is sandy loam. Organic matter content is 2.50%,
wet aggregate stability is 29% and bulk density is 1.55 Mg m–3 of the soil (Gundogan
et al., 2019). Parent material is on conglomerate-marl alternate and inclination is 12%.
2.2 Experimental design
In the study area, 24 parcels were prepared according to the randomised block design in
factorial order with three replications. The length and width of each parcel were 35 m and
5 m, respectively. Two tillage systems (TT and RT) with two crops (wheat and sainfoin)
were applied in the experimental studies. In the TT, deep plow was applied once by using
a plough, and soil was cultivated twice with disc harrow, then the seed bed was prepared
by using a packer. The wheat and sainfoin cultivations were made with suitable seed
sowing machines. In the RT, after the seed bed was prepared using coulter and roller pair
(combination), wheat and sainfoin seeds were scattered by hand. Sowing was carried out
on 15 November 2015 for both tillage methods.
In order to evaluate the effects of management systems on the variables to be
measured, a fallow plot was prepared for each case. Thus, total number of parcels
including replications was 24 (three TT-wheat, three TT-sainfoin, six TT-fallow,
three RT-wheat, three RT-sainfoin and six RT-fallow) in the field. The seeds of wheat
(Triticum aestivium L.) and the sainfoin (Onobrychis sativa L. varieties) were used as
they are the most common seeds used in the region. Along with the seeds, 200 kg ha–1 of
DAP fertiliser (18% NH4+–N, 46% P2O5, w/w) was applied as base fertiliser. For weed
control, there was no need to use chemicals; they were collected by hand in the parcels of
wheat, sainfoin and fallow. In addition, spring fertilisation was carried out in March using
200 kg ha-1 of CAN fertiliser (13% NH4+–N, 13% NO3–N, w/w).
2.3 Sediment collection procedure
After seeding into the parcels, the channels with a depth of 20 cm were opened around
each parcel by arc plow, and then the yellow-coloured ondulines corrugated roofing was
placed on these channels to prevent water flow from inside and outside. Also on the
lower edge of the parcels, geotextiles were stretched at certain height to collect sediment
delivered from the parcels through the surface runoff (Figure 1). On the 23rd of June
2016, wheat harvest was performed for the first year, but sainfoin was not harvested in
the first year since it was not developed enough to be harvested.
At the end of the hydrological year, sediment delivered to the geotextile from the
parcels with natural rainfalls were collected and recorded as sediment yield for the first
hydrological year. On the 15th of November 2016, wheat seeds were planted for the
second year. On the 7th of June 2017, the harvesting process was performed in both
wheat and sainfoin parcels. At the end of the second water year, sediment delivered to the
geotextile from the parcels with natural rainfalls were collected and evaluated as
sediment yield for the second hydrological year. Since wind erosion is ineffective in the
region, a small amount of possible sediment carried by wind to silt-fens has not been
taken into account in the calculations.
398 T. Yakupoglu et al.
In order to compare the sediment yields accurately, the sediments accumulated in
geotextiles were collected at the same date in both years. In addition, since the rainfall
amounts and characteristics are different for two years, the sediment yields of these
two hydrological years were also evaluated considering the unit rainfalls by using the
actual rainfall data of experimental area. Rainfall measurements were made by R-Fuess
brand syphon type pluviometer which can record data for 24 hours.
Figure 1 Experiment parcels, (a) view of parcels from uphill, (b) view of parcels from downhill,
(c) sowing with machinery and (d) view of parcels after germination (see online version
for colours)
(a) (b)
(c) (d)
3 Data analysis
An ANOVA test was applied to data which show a normal distribution (Shapiro-Wilk
test) to evaluate the effects of the cases on the measured variables, and Duncan test
(α = 0.05) was used for multiple comparisons. These statistical analyses were performed
using SPSS version 20 computer program (Efe et al., 2000).
The effect of traditional and reduced tillage systems 399
4 Results
4.1 Rain data of experiment site
It was found that, total rainfall was 433.6 mm in hydrological year of 2015–2016. The
next year was more humid and the total rainfall was 727.1 mm. Table 1 shows the
rainfalls in two hydrological years (2015–2016 and 2016–2017). The difference between
the two hydrological years is due to the difference of the annual rainfall patterns as seen
from the monthly amount of rainfall.
Table 1 Natural rainfall data (mm) for the hydrological years of 2015–2016 and 2016–2017
Years Months
X XI XII I II III IV V VI VII VIII IX Total
2015–2016 35.0* 20.4 1.5 106.1 59.3 86.7 9.3 35.7 24.4 1.3 0.0 88.9 433.6
2016–2017 0.0** 18.0 332.3 76.0 0 122.2 114.8 50.2 8.9 0 0.8 3.9 727.1
Note: *Since seed cultivation was carried out in November, the rainfall received in this
month was ignored in calculations.
**In the second hydrological year, no rainfall occurred in November.
4.2 Sediment yield of parcels
The comparison of the average sediment yield received from the parcels in both
hydrological years is presented in Figure 2. It was found that the amount of sediment
transported in the second year was lower than the first year, which was valid for all
parcels. For the both years, the most amount of sediment was transported from fallow
parcels treated with TT system (478 kg ha–1, Std. dev. = 133 kg ha–1 for 2015–2016 and
303 kg ha–1, Std. dev. = 132 kg ha–1 for 2016–2017) while the least amount of sediment
was from the sainfoin planted parcels treated with reduced tillage system (16 kg ha–1,
Std. dev. = 4 kg ha–1 for 2015–2016 and 9 kg ha–1, Std. dev.= 2 kg ha–1 for 2016–2017).
Although there is no statistically significant difference between the total sediment yields
of the parcels between the hydrological years, the total sediment yield in the second
hydrological year is less than that of the first one, which can be attributed to the different
rainfall patterns between these hydrological years.
Table 2 Duncan multiple comparison test results for sediment yield (kg ha–1)
Cover N Subset
Sainfoin 4 38.7500b
Wheat 4 67.5000b
Fallow 8 280.3750a
Notes: The error term is mean square (error) = 4,282.375, α = 0.05. Lowercase letters
next to the subset value, such as a and b, indicate whether there is a difference
between groups. There is no statistical difference between groups that receive the
same letter and vice versa.
400 T. Yakupoglu et al.
According to variance analysis (ANOVA), the difference between the total amount of
sediments in two hydrological years was statistically insignificant. However, the effects
of soil tillage system and vegetation cover (crop type) on sediment yield were found to be
significant at the level of P < 0.05 and P < 0.01, respectively. The results of the multiple
comparison test indicating the effects of the crop status on the sediment yield was given
in Table 2. It was found that the maximum amount of sediment was transported from
fallow parcels. The least amount of sediment was transported from the sainfoin planted
parcels, but the amount of sediment yield from wheat and sainfoin planted parcels was
not statistically different from each other.
Figure 2 Comparison of parcels in terms of sediment yield for two hydrological years (see online
version for colours)
4.3 Sediment quantity per unit rainfall
Comparison of parcels in terms of sediment quantity per unit rainfall in two hydrological
years was shown in Figure 3. It was found that the amount of sediment transported from
the unit rainfall in the second year was lower than the first water year for the all parcels.
For the both years, the most sediment with the unit rainfall was carried from the fallow
parcel treated with the TT system (1,103 g ha–1 mm–1, Std. dev. = 175 g ha–1 mm–1 for
2015–2016 and 477 g ha–1 mm–1, Std. dev. = 181 g ha–1 mm–1 for 2016–2017) while the
least sediment was carried from the sainfoin planted parcel treated with RT system
(38 g ha–1 mm–1, Std. dev. = 9 g ha–1 mm–1 for 2015–2016 and 12 g ha–1 mm–1, Std. dev.
= 3 g ha–1 mm–1 for 2016–2017).
According to the results of ANOVA, the amount of sediment transported from the
parcels per unit rainfall was different in both hydrological years and this difference was
statistically significant (P < 0.05). In addition, the sediment yield per unit rainfall was
affected statistically by the vegetation cover condition of the parcels (P 0.01). The
effect of tillage system on the sediment yield of the parcels per unit rainfall was
statistically insignificant. The Duncan test was used to compare the average sediment
yield from the parcels per unit rainfall with respect to vegetation cover. It was found that
The effect of traditional and reduced tillage systems 401
the highest sediment yield per unit rainfall was transported from the fallow parcel
(Table 3). The amount of sediment yield per unit rainfall from the parcels with vegetation
cover was less than that of the fallow parcel and this difference was statistically
significant. However, the sediment yield per unit rainfall from the sainfoin planted
parcels was less than the sediment yield per unit rainfall from the wheat planted parcels,
however, the difference was no statistically different.
Figure 3 Comparisons of parcels in terms of sediment quantity per unit rainfall for
two hydrological years (see online version for colours)
Table 3 Duncan multiple comparison test results for sediment yield per unit rainfall
(g ha–1 mm–1)
Cover N Subset
Sainfoin 4 77.0b
Wheat 4 133.25b
Fallow 8 540.25a
Notes: The error term is mean square (error) = 21,464.25, α = 0.05. Lowercase letters
next to the subset value, such as a and b, indicate whether there is a difference
between groups. There is no statistical difference between groups that receive the
same letter and vice versa.
4.4 Comparison of tillage systems and hydrological years
The comparison of tillage systems in terms of sediment yield and the comparison of
two different hydrological years with respect to sediment quantity per unit rainfall were
given in Figure 4. It was found that the average sediment yield in the second year was
lower than the average sediment yield in the first year. The difference of the sediment
yield per unit rainfall between these two years was statistically significant. In addition,
the amount of sediment transported from the RT parcels was less than the amount of
sediment transported from the TT parcels and the difference was found to be statistically
significant.
402 T. Yakupoglu et al.
Figure 4 Subject effects on measured variables, (a) comparison of tillage systems in terms of
sediment quantity (b) comparison of hydrological years in terms of sediment quantity
per unit rainfall (see online version for colours)
(a) (b)
5 Discussion
The difference in rainfall pattern in both hydrological years resulted in that the sediment
amount transported from the experimental parcels was to be different. Another reason for
the different sediment yield at the experimental parcels was that the total amount of
rainfall in the hydrological years was also different. Even though the kinetic energy of
rainfall, which is a function of the physical properties of rainfall, is the most important
effect of rainfall on the erosion, the total rainfall depth can be effective on the amount of
sediment yield (de Lima et al., 2013). In addition to the total amount of precipitation,
rainfall pattern affects the amount of sediment transported (Mohamadi and Kavian, 2015;
Xu et al., 2018).
The significant differences between the amount of sediment transported from the
parcels treated with the traditional and RT systems can be primarily explained by the fact
that the effect of tillage systems on soil structural stability was different. When TT
systems are applied, the stability of aggregates (macroaggregates) larger than 250 µm
decreases (Kasper et al., 2009) and the air-water balance is failed in the tillage layer. In
TT systems, the pore connectivity is interrupted in treated soil layer because of the large
number of machines intervening. On the other hand, increased field traffic causes a
compaction in the lower layers (Hu et al., 2018) and the pore geometry changes.
In a similar study conducted on natural precipitation in a medium-scale
Mediterranean basin, it was indicated that sediment yield was statistically significantly
correlated with the surface runoff rate (Tuset et al., 2016). The previous studies, where
traditional and RT systems have been compared in terms of their effects on erosion,
reported that soil quality can be preserved and erosion can be decreased in different rates
by using RT systems (Husnjak et al., 2002; Fallahi and Raoufat, 2008).
The results of this study indicated that both the amount of sediment and the amount of
sediment per unit rainfall transported from fallow parcels were statistically different due
to the fact that the surface of the fallow parcel was not covered. When the soil surface is
not covered, the rain drop transmits its energy directly to the soil and this energy causes
The effect of traditional and reduced tillage systems 403
fragmentation of the soil. However, when the soil surface is covered with crops, the
energy of the rain drop is distributed by the crop cover. Thus, the fragmentation of the
soil is prevented at different levels and sediment transportation is reduced with
concentrated surface runoff (Bingner et al., 1992; Vaezi et al., 2017).
According to the results of experimental studies, both the amount of sediment and the
amount of sediment per unit rainfall transported from parcels covered with crops were
lower due to the fact that wheat and sainfoin roots could have a positive effect on
aggregation in the soil for two years. As it is well known, the roots contribute to the
stability of the aggregate by the effect of the adhesives and the enmeshment effect of the
capillary roots. On the other hand, when the roots use water in the rhizosphere,
rehydration contributes to aggregation by allowing soil particles to approach each other.
The growth of developmental roots under the ground also brings the soil particles closer
together (Angers and Caron, 1998). The results of presented study also revealed that the
presence of roots in the crop planted parcels maintained the pore continuity by preserving
the aggregates relatively, reducing the infiltration rate and decreasing the hydraulic
conductivity, thus reducing the surface flow. As a result, the sediment yield was reduced.
When the parcels with different crops were compared with respect to sediment yields
and sediment yields per unit rainfall, it is seen that the sediment yield from the sainfoin
planted parcels was lower than that of wheat planted parcels. However, it was found that
the difference was not statistically significant. The low sediment yield from the sainfoin
planted parcels can be explained based on the fact that the sainfoin as perennial crop
covers the parcel for longer period of time compared to wheat which is an annual
crop, therefore, the sainfoin planted parcels were less affected by rainfall during the
post-harvest period (i.e., July, August, September and October).
Statistical analysis indicated that there was no significant difference in sediment
yields between two hydrological years. This means that approximately the same amount
of sediment occurred in both years. However, the total amount of rainfalls and the rainfall
patterns were different in two hydrological years. The rainfall pattern, which is one of the
main variables affecting sediment yield (Wei et al., 2015), is a very complex subject
(de Lima et al., 2013). Therefore, it is more meaningful and realistic to evaluate the
amount of sediment per unit rainfall in both years.
Comparing the hydrological years in terms of sediment yield per unit rainfall, it was
found that sediment yield of the second year was less than that of the first year (Figure 4)
and the difference between years was statistically significant. This result can be explained
by the fact that there was not enough sainfoin and wheat residue on the soil in the first
year; especially the residues of harvested wheat are not decomposed in the soil. Besides,
vegetatively undeveloped crops could not adequately protect the soil from rainfall in the
first hydrological year. It is known that the vegetative residues contribute to aggregation
when they decomposed in soil (Puget et al., 2000). Thus, it can be also concluded that the
significant decrease in sediment yield per unit of rainfall in the second year was due to
the positive effect of the humificated plant material on the structural stability in the soil.
6 Conclusions
According to the results, it was found that the sediment yields transported from the
parcels were affected by tillage systems and existence of plant production in the parcels.
404 T. Yakupoglu et al.
It was also found that the most sediment was transported from fallow parcels while the
least sediment was transported from the sainfoin planted parcel. There was no significant
difference between the sediment amounts transported from the sainfoin planted parcels
and wheat planted parcels. The difference between the total amounts of sediment yields
recorded in two hydrological years was not significant, while sediment yield per unit
rainfall was different from each other. The amount of sediment yield per unit rainfall in
the second year was less than the amount of sediment yield per unit rainfall in the first
year. The results of the study shows that the agricultural lands without crop cover
increases water erosion in the Mediterranean climate zone, which is more susceptible to
climate change than other regions. The rainfall pattern and the applied soil tillage system
are effective factors on this erosion. Therefore, the soil should be kept under crop cover
as long as possible, the rainfall pattern should be taken into consideration during the
implementation of protection measures, and RT systems should be applied. The RT
system we used in this study (one time coulter and roller pair combination) is suitable for
wheat and sainfoin cultivation in this region. In order to develop suitable methods for
erosion control in the semi-arid regions of the Mediterranean climate zone, at least ten
years of climate change-erosion studies should be planned and different crops and variety
of tillage systems should be considered in these studies.
Acknowledgements
This study financially supported by The Scientific and Technological Research Council
of Turkey (TUBITAK, Project No: 114R052). In addition, this project is under a COST
action which is briefly called Connecteur (COST Action Code: ES1306). We would like
to thank the aforementioned institutions and organisations.
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