Long-Term Tillage Induced Changes in Physical Attributes of a Clayey Soil in Eastern Mediterranean Region

DOI: 10.2478/alife-2018-0005

LONG-TERM TILLAGE INDUCED CHANGES IN PHYSICAL

ATTRIBUTES OF A CLAYEY SOIL

IN EASTERN MEDITERRANEAN REGION

, Hikmet GÜNAL2, Mert ACAR1, Zeliha BARUT BEREKET3, Nurullah ACİR4, Mesut BUDAK5

1

Çukurova University, Faculty of Agriculture, Department of Soil Science and Plant Nutrition, Adana, Turkey

2

Gaziosmanpaşa University, Faculty of Agriculture, Department of Soil Science and Plant Nutrition, Tokat, Turkey

3

Çukurova University, Faculty of Agriculture, Department of Agricultural Machinery, Adana, Turkey

4

Ahi Evran University, Faculty of Agriculture, Department of Soil Science and Plant Nutrition, Kırşehir, Turkey

5

Siirt University, Faculty of Agriculture, Department of Soil Science and Plant Nutrition, Siirt, Turkey

Corresponding author email: icelik@cu.edu.tr

Abstract

Comparing responses of the same soil under long-term different treatments is vital in determining the best management practices to conserve soil health and sustain productivity. This study was investigated to determine the effects of long-term (2006-2015) two conventional (CT), three reduced (RT) and a no-till (NT) treatment on bulk density (BD), field capacity (FC), wilting point (WP), available water content (AWC) and total porosity (TP) of a clayey soil in eastern Mediterranean region, Turkey. Undisturbed soil samples were collected from 0-10, 10-20 and 20-30 cm depths of experimental plots with a crop rotation of winter wheat (Triticum aestivum L.), soybean (Glycine max. L.), grain maize (Zea mays L.). The AWC under CT was higher than the RT and NT. The BD was increased with depth in all treatments, and was higher under RT and NT than the CT. The long-term experiment revealed that BD increase under long-term RT and NT should be monitored to avoid deterioration of soil health, and yield loss due to limiting root penetration and storing available water needed during drought periods.

Keywords: available water, no-till, reduced till, conventional, bulk density. INTRODUCTION

Çukurova of eastern Mediterranean is one of the largest and most intensively used agricul-tural plains of Turkey. Despite worldwide recognition of conservation tillage (reduced (RT) and no-till (NT) systems) as the best sustainable management alternative to conven-tional practices (Verhulst et al., 2010), farmers in Turkey continues to use traditional intensive tillage (mouldboard ploughing) systems (Celik et al., 2012). Long term intensive conventional tillage practices that is the main cause of soil organic matter loss and structural degradation in Mediterranean region (Martin-Lammerding et al., 2013) threatens the sustainability of agricultural production by reducing fertility and

productivity. Although legally prohibited, crop residues are being widely burned prior to tillage (Çelik, 2011; Korucu et al., 2009). Burning residue may lead low soil resilience to degra-dation, aggregation and direct infiltration, and thus considered as an inappropriate mana-gement option. On the other hand, conservation tillage leaves at least thirty percent of harvest residue on the soil surface that leads to increase infiltration, improves soil moisture retention and reduces runoff (Salem et al., 2015).

The level of soil disturbance influences the extent of tillage impact on soil properties (Blanco-Canqui et al., 2017), i.e., ability of soil to adsorb and retain water, resistance to dete-rioration of water stable aggregates and etc. In addition to level of soil disturbance, differences

in soil type of the experimental site, frequency of tillage operations, rotations, rooting charac-teristics of plants, climate of the study area, duration of the experiment and many other dynamic and inherent features may change the impact of tillage systems on soil characteristics. Differences in dynamic or genetic features of experimental sites or conditions of the experiment cause to some contradictory results on the impacts of tillage practices on soil physical properties. For example, the increased bulk density (BD) and decreased total porosity under NT compared to conventional tillage (CT) system were reported from a typic Argiudoll in Argentina (Sasal et al., 2006). In another study from eight different locations of Great Plains, USA, Pikul et al. (2006) reported increase, decrease or non-significant change in BD of surface soils. In contrast, Das et al. (2014) found significantly lower bulk density values under NT and RT systems. The researchers concluded that higher organic matter accumulation on surface soils of NT and RT resulted in lower bulk density compared to intensively tilled soils under CT. Similar contrasting results have been reported for other physical soil properties.

Long term experimental sites are needed to convince the Turkish farmers to change their customs and integrate conservative tillage options into Turkish farming system. This long-term study is one of the few efforts ongoing in Turkey to show the effects of different tillage systems. The aim of this report is to present the impacts of nine-year six tillage systems on some of functional physical properties of a clayey soils in Çukurova plain of eastern Mediterranean, Turkey.

MATERIALS AND METHODS Study Area

The experiment was established in 2006 at the Agricultural Experimental Station of the Çukurova University, in Adana eastern Mediterranean, Turkey. According to the Köppen classification, the climate of the region is hot dry summer (Csa), with annual average temperature of 19.2 °C. The average annual total precipitation is 639 mm, about 75% of which falls during the winter and spring. The

experiment was established on a fine, smectitic, active, mesic Typic Haploxerert soil that formed over old terraces of Seyhan River.

Soil texture of the experimental site is composed of 50% clay, 32% silt and 18% sand, and mean pH is 7.82, electrical conductivity is 0.15 dS m-1, calcium carbonate is 244 g kg-1 at 0-30 cm soil depth (Çelik, 2011).

Experimental Design and Tillage Systems

The experiment was designed as a randomized complete-block three replicates. The plots were 12-m width and 40-m length (480 m2) with 4 m buffer between each plot. In this study, six tillage systems in rotation of winter wheat (Triticum aestivum L.), soybean (Glycine max.

L.) – grain maize (Zea mays L.) were applied

for nine years.

In all tillage methods, the harvest residues on soil surface were chopped prior to tillage opera-tions except CT-2. The tillage treatments were:

1.) Conventional tillage with residue

incur-porated (CT-1): In CT-1, soil was tilled to 30-33 cm depth using a moldboard plow before winter wheat followed by two passes of disc harrow at 13-15 cm and 2 passes of float. For the second crop, soil was tilled with a heavy tandem disc harrow (HTD) to a depth of 18 to 20 cm, followed by 2 passes of disc harrow to 13-15 cm depth and 2 passes of float.

2.) Conventional tillage with residue burned

(CT-2); In CT-2, crop residues were burned after each harvest differed from CT-1 and also chisel plow instead of HTD to the depth of 35 to 38 cm was used in second crop.

3.) Reduced tillage with heavy tandem disc

harrow (RT-1); In RT-1, soil was tilled with a HTD to a depth of 18-20 cm (2 passes) and followed by 2 passes of float before wheat planting. For the second crop, rotary tiller (RoT) was used to 13-15 cm depth and 2 passes of float.

4.) Reduced tillage with rotary tiller (RT-2); In

RT-2, RoT was used at 13-15 cm depth and followed by 2 passes of float before first and second crop planting.

5.) Reduced tillage with heavy tandem disc

harrow followed by no tillage for the second crop (RT-3); In RT-3, soil was tilled with a HTD to 18-20 cm depth and followed by 2 passes of float before wheat. A non-selective herbicide (500 g ha-1 Glyphosate) was applied

for weed management, and NT planter was used for planting of second crop soybean or corn.

6.) No-tillage, direct planting (NT); In NT, crop

residue on soil surface were chopped as in all other treatments except CT-2, a non-selective herbicide (500 g ha-1 Glyphosate) was applied for weed management, and NT planter was used for planting in both the first and the second crop.

Chemical fertilizer application rate was the same regardless of tillage method: 170-180 kg N ha-1 and 55-60 kg P2O5 ha-1 for wheat, 250-265 kg N ha-1 and 60-65 kg P2O5 ha-1 for corn and 120-130 kg N ha-1 and 40-45 kg P2O5 ha-1 for soybean based on soil analysis. Commercially available corn and soybean cultivars at seeding rates of 8.4 and 23.6 plants per m2 were planted in the third week of June and harvested in the second week of October.

Soil Samplings and Laboratory Analyses

Three individual disturbed and undisturbed soil samples at the 0-10, 10-20 and 20-30 cm depths were taken after second crop harvest of corn in 15th of December, 2015. The disturbed samples were used to determine the water content at permanent wild point (WP). The undisturbed soil cores were taken with metallic rings to determine bulk density (BD), porosity (micro, macro and total) and water content at field capacity (FC).

Bulk density was determined using soil cores (length 5.1 cm, diameter 5.0 cm) collected from three depths. The soil samples of known volumes were weighed, oven dried at 105 ºC for 24 h to a constant weight and weighed to calculate bulk density (Blake and Hartge, 1986).

Total porosity (TP) was determined in undisturbed water-saturated samples of 100 cm3 assuming no air trapped in the pores and its validity checked using dry bulk density and average particle density (2.65 g cm−3) values (Danielson and Sutherland, 1986). The pores smaller than 4.5 μm radius are defined as micropores (Mi) which was determined from the volumetric water content, using a pressure membrane at FC (− 33 kPa). Macro pores (radius > 4.5 μm) was calculated as the difference between TP and Mi (Danielson and Sutherland, 1986). The core samples were

capillary saturated and equilibrated to FC (-33 kPa) matric potentials in a pressure plate (Klute, 1986). Soil moisture at -1500 kPa matric potential (WP) was determined using disturbed soil samples with a method described by Klute (1986). Available water content (AWC) was computed as the difference in water content between FC and WP.

Statistical Analyses

Kolmogorov–Smirnov test was used to control the distribution of data for normality. The data had normal distribution and no need to use any kind of transformation to normalize the data. The effects of tillage systems and the differences among tillage systems were assessed by analysis of variance (ANOVA) test. Differences among the treatments were evaluated by DUNCAN test (P<0.05). The statistical analyses were performed using IBM SPSS statistical package (version 21.0, SPSS Inc., Chicago, IL).

RESULTS AND DISCUSSIONS Bulk Density and Porosity

The average bulk density (BD), micro (Mi), macro (Ma) and total porosity (TP) of soil for all tillage practices under wheat, soybean-corn rotation are presented in Table 1. The two-way ANOVA test indicated that the impacts of tillage systems (P ˂ 0.05) and soil depth (P ˂ 0.01) on BD were significant, but the tillage x depth interaction was non-significant (P = 0.988). Soil BD in 0-10 cm under all tillage systems were lower than that in 10-20 and 20-30 cm, although the differences in BD values among tillage systems were not significant at all three depths.

The variation of BD with the depth is only significant (P<0.01) under NT system, and BD values at different depths under other five tillage systems were not significantly different between depths. The BD value was ranged from 1.34 (CT-2) to 1.42 g cm-3 (RT-2), from 1.42 (CT-2) to 1.52 g cm-3 (RT-2) and 1.38 (CT-2) to 1.49 g cm-3 (RT-2, RT-3) in 0-10, 10-20 and 20-30 cm depths, respectively (Table 1). After 9 years of tillage operations, the NT and RT resulted in higher BD values in all three depths compared to the BD values under CT-1 and CT-2, intensively tilled systems. Although

non-significant except under NT, the increase in BD with depth is an indication of a clear stratification in all tillage systems with lower BD in the surface soil. Moraes et al. (2016) indicated that pulverization at surface layer under CT leads to lower BD and macroporosity compared to RT and NT systems. Higher BD values under NT and RT managements are related to the absence or minimal mechanical disturbance (Tormena et al., 2017), while lower BD values under CT managements resulted from loosening of upper 30 cm depths of soil profile by frequent mouldboard tillage operations.

Similar to the results obtained in this study, Karlen et al. (2013) reported non-significant influence of tillage systems on BD in 0-5 cm depth under corn/soybean rotation and conti-nuous corn production.

In contrast to higher BD values under NT and RT systems compared to CT, Karlen et al. (2013) stated that frequent tillage operations under CT resulted in greater break up, incorporation, and oxidation of above- and below-ground plant residues which resulted in significantly higher BD under CT management compared to NT.

Our results are consistent with the findings of Martin-Lammerding et al. (2013) who found significantly different BD values in 0-7.5 cm depth under different tillage systems. The BD under NT plots were the highest (1.52 g cm-3), as in our case, and followed by BD under CT (1.38 g cm-3) and RT (1.24 g cm-3) (Martin-Lammerding et al., 2013).

Similarly, Blanco-Canqui et al. (2004) have also reported no significant differences between long-term NT and chisel plough treatments. Table 1. Tillage effects on bulk density, micro, macro and total porosity

Tillage Methods Bulk Density (g cm-3) Micro Porosity (cm3 cm-3) Macro Porosity (cm3 cm-3) Total Porosity (cm3 cm-3) 0-10 cm

CT-1 1.35#±0.05†a&ns 0.37±0.01b** 0.17±0.03a* 0.55±0.02a ns

CT-2 1.34±0.03 a ns 0.38±0.01ab ns 0.17±0.02a ns 0.55±0.01a ns

RT-1 1.35±0.04 a ns 0.39±0.01ab ns 0.16±0.02a ns 0.54±0.01a ns

RT-2 1.42±0.03 a ns 0.41±0.00a* 0.09±0.01a ns 0.50±0.01a ns

RT-3 1.36±0.05 a ns 0.39±0.01ab ns 0.15±0.04a ns 0.54±0.03a ns

NT 1.37±0.03 a ** 0.40±0.01ab ns 0.15±0.02a * 0.54±0.02a ns

ANOVA 0.836 0.172 0.487 0.742 10-20 cm CT-1 1.44±0.03 a 0.42±0.01 a 0.11±0.01 a 0.53±0.01 a CT-2 1.42±0.02 a 0.40±0.01 a 0.14±0.01 a 0.54±0.01 a RT-1 1.44±0.03 a 0.39±0.01 a 0.13±0.02 a 0.51±0.02 ab RT-2 1.52±0.02 a 0.39±0.01 a 0.09±0.01 a 0.48±0.01 b RT-3 1.46±0.05 a 0.40±0.02 a 0.11±0.03 a 0.51±0.02 ab NT 1.49±0.03 a 0.41±0.01 a 0.09±0.01 a 0.50±0.01 ab ANOVA 0.347 0.178 0.372 0.133 20-30 cm CT-1 1.45±0.03 ab 0.43±0.01 a 0.10±0.01 a 0.53±0.00 a CT-2 1.38±0.02 b 0.39±0.01 bc 0.13±0.01 a 0.52±0.00 a RT-1 1.47±0.03 ab 0.40±0.01 bc 0.11±0.01 a 0.51±0.01 a RT-2 1.49±0.04 a 0.38±0.01 c 0.12±0.02 a 0.49±0.01 a RT-3 1.49±0.03 a 0.41±0.01 ab 0.10±0.01 a 0.50±0.01 a NT 1.48±0.04 a 0.41±0.01 ab 0.09±0.01 a 0.51±0.02 a ANOVA 0.166 0.015 0.337 0.467 Tillage 0.031 0.052 0.117 0.036 Depth 0.000 0.062 0.002 0.008 Tillage x Depth 0.988 0.014 0.747 0.993

CT-1: Conventional tillage with residue incorporated, CT-2: Conventional tillage with residue burned, RT-1: Reduced

tillage with heavy tandem disc harrow, RT-2: Reduced tillage with rotary tiller, RT-3: Reduced tillage with heavy tandem disc harrow followed by no tillage for the second crop, NT: No-tillage, direct planting, #: Average of three plots, †: Standard error of the means, &: Different letters in a column indicate significant differences (P < 0.05) among different tillage systems. Changes with depth obtained in Duncan test **: Significant at p<0.01, *: p<0.05; ns: Not significant.

An analysis of variance indicated that tillage systems had non-significant effects on Mi (except 20-30 cm), Ma and TP of soils in all three soil depths. The two-way ANOVA revealed that Mi, defined as storage pores (Glab and Kulig, 2008) did not significantly change by tillage systems and depth, though significant tillage x depth interaction was defined. In contrast to Mi, tillage systems (P = 0.036) and depth (P ˂ 0.01) had significant effects on TP, but there was no significant tillage x depth interaction. The tillage did not have a significant impact on Ma which is defined as transmission pores (Glab and Kulig, 2008). Tillage x depth interaction was also not defined for Ma, but TP significant differed by depth. Our results for effect of depth on porosity are partially comply with those repor-ted by Capowiez et al. (2009) who found signi-ficant effect of depth on all classes of porosity. At the 0-10 cm depth, the lowest Ma fraction (0.09 cm3 cm-3) was obtained under RT-2 whereas the opposite was observed for Mi. The use of rotary tiller to a depth of 13-15 cm both for wheat and second crop seedbed prepara-tions under RT-2 management reduced the Ma below the value of 0.01 cm3 cm-3 is defined a critical limit for plant growth to supply adequate oxygen (Hâkansson and Lipiec, 2000). The Ma fraction under other tillage systems in 0-10 cm were higher than 0.10 cm3 cm-3. The Ma under all tillage systems (except RT-2) decreased with depth, and was very close to or lower than the critical value of 0.10 cm3 cm-3 under most of tillage systems. The Ma was 41.2 and 40% higher at 0-10 cm (0.17 and 0.15 cm3 cm-3) than at 20-30 cm depth (0.10 and 0.09 cm3 cm-3) under CT-1 and NT. The results showed that tillage in RT and CT, and residue accumulation in NT systems favoured the higher Ma fraction in surface soils compared to subsurface layers.

Our results on variation of Mi fraction with depth are not consistent with those reported by Kay and VandenBygaart (2002) who found indicated that disaggregation of soil structure under CT leads to an increase in Ma fraction with depth. However, we found that the fraction of Mi significantly increased from 0.37 (0-10 cm) to 0.43 cm3 cm-3 (20-30 cm) under CT-1, and it was reduced from 0.41 (0-10 cm) to 0.38 cm3 cm-3 under RT-2 (20-30 cm) management. In other four tillage systems, the

increase or decrease in Mi fraction with depth was not significant.

Total porosity of soils ranged from 0.50 (RT-2) to 0.55 (CT-1, CT2) cm3 cm-3 at 0-10 cm, from 0.48 (RT-2) to 0.54 (CT-2) cm3 cm-3 at 10-20 cm and from 0.49 (RT-2) to 0.53 (CT-1) cm3 cm-3 at 20-30 cm. The TP, likewise in Ma under RT and NT systems were lower than that of the CT systems at all three depths. Our results are consistent with those reported by Mishra and Kushwaha (2016) with regard to effective porosity and also plant available water capacity of soils having CT for over two years compared to deep tillage and NT systems. Similarly, Salem et al. (2015) have found lower total porosity under NT system compared to RT and CT practices. They have also indicated no significant differences of TP between RT and CT practices in most soil layers.

The TP has decreased with depth in all tillage systems, but the rate of decrease was not a significant level in all systems. The decrease in TP under RT and NT systems may be com-pensated by the development of more stable, continuous macro pore network due to the absence or minimal soil disturbance and active-ties of soil organisms (Soane et al., 2012). But the decline under CT systems will get worsen due to the destructive impact of continuous tillage operations.

Water Contents at Field Capacity, Perma-nent Wilting and Available Water Content

Tillage systems did not significant change the water content at field capacity (FC) except in 20-30 cm depth, whereas water content at permanent wilting point (WP) was significantly different at all three depths among six tillage systems (Table 2). The FC values in three depths were significantly different under CT-1 (P˂0.01) and RT-2 (P˂0.05), and it was similar under other four tillage systems. The WP values in three depths were slightly differed under CT-2 (P˂0.05) treatment. Available water content (AWC) in 0-10 cm was similar among tillage systems, whereas the AWC in 10-20 and 10-20 cm depths was significantly different (P˂0.01) among tillage systems due to the significant change in WP. The depth distribution of AWC was slightly different (P˂0.05) under RT-1 and significantly different under CT-1 and RT-2 (P˂0.01).

Table 2. Tillage effects on field capacity, permanent wilting point and available water content

Tillage Methods Field Capacity (%) Permanent Wilting Point (%) Available Water (%)

0-10 cm

CT-1 37.25#±1.32†b&** 27.15±1.14bc ns 10.09±0.72ab**

CT-2 38.12±0.82ab ns 25.57±0.45c* 12.55±0.77a ns

RT-1 38.69±1.21ab ns 28.01±0.93abc ns 10.67±0.92ab*

RT-2 40.92±0.46a* 28.97±0.37ab ns 11.95±0.64ab**

RT-3 39.14±1.50ab ns 28.34±0.86ab ns 10.80±0.73ab ns

NT 40.01±0.67ab ns 30.30±0.69a ns 9.71±0.68b ns ANOVA 0.172 0.002 0.083 10-20 cm CT-1 41.92±0.82 a 29.10±0.86 bc 12.82±0.47 a CT-2 40.15±0.84 a 27.70±0.60 c 12.44±0.72 a RT-1 38.73±1.25 a 30.67±1.20 ab 8.06±0.41 b RT-2 39.14±0.74 a 30.95±0.55 ab 8.19±0.74 b RT-3 39.80±1.58 a 30.04±0.66 ab 9.76±1.36 b NT 41.52±0.53 a 32.44±0.84 a 9.08±0.69 b ANOVA 0.178 0.003 0.000 20-30 cm CT-1 42.67±0.84 a 29.06±0.64 ab 13.61±0.57 a CT-2 39.00±1.36 bc 27.66±0.64 b 11.34±1.07 b RT-1 39.72±0.54 bc 30.82±0.83 a 8.90±0.47 bc RT-2 37.64±0.73 c 30.17±1.13 a 7.47±0.74 c RT-3 40.78±0.78 ab 30.06±0.33 a 10.71±1.00 b NT 41.14±0.75 ab 31.08±0.77 a 10.06±0.60 b ANOVA 0.015 0.014 0.000 Tillage 0.052 0.000 0.000 Depth 0.062 0.000 0.121 Tillage x Depth 0.014 0.991 0.001

CT-1: Conventional tillage with residue incorporated, CT-2: Conventional tillage with residue burned, RT-1: Reduced

tillage with heavy tandem disc harrow, RT-2: Reduced tillage with rotary tiller, RT-3: Reduced tillage with heavy tandem disc harrow followed by no tillage for the second crop, NT: No-tillage, direct planting, #: Average of three plots, †: Standard error of the means, &: Different letters in a column indicate significant differences (P < 0.05) among different tillage systems. Changes with depth obtained in Duncan test **: Significant at p<0.01, *: p<0.05; ns: Not significant.

The two-way ANOVA indicated non-significant effects of tillage systems and depth on FC, though a significant (P˂0.05) tillage x depth interaction was defined. In contrast to FC, two-way analyse of variance test showed significant effects (P˂0.01) of tillage systems and depth on WP, and non-significant (P=0.991) tillage x depth interaction for WP. The two-way ANOVA revealed a significant effect (P˂0.01) of tillage systems and tillage x depth interaction on AWC, and non-significant (P=0.121) influence of depth for AWC.

The AWC ranged from 9.71 (NT) to 12.55% (CT-2), from 8.06 (RT-1) to 12.82% (CT-1), and from 7.47 (RT-2) to 13.61% (CT-1) in 0-10, 10-20 and 20-30 cm depths, respectively. The increased Mi fraction with depth under CT-1, one of the more intensively disturbed systems, resulted in increased AWC. Similar results have been presented by Tormena et al.

(2017) who indicated that reduction in volume of conducting Ma and increase in capillary pores by the redistribution of pore sizes under chisel ploughing led to a higher water retention of soil structure.

The decrease in pore diameter results in greater water retention at higher water potentials. In contrast to higher water retention under CT management, the volume of Mi and Ma pores were reduced under NT and RT systems which resulted in decreased water retention.

The water retention capacity of soils at subsurface layers under CT practices are higher compared to RT and NT systems, though we should keep in mind that the presence of crop residue on soil surface under RT and NT efficiently decreases the evaporation compared to CT.

Under dry and hot summer days of Mediterranean climate, the decline in

evaporation will have significant benefits for crop production which may compensate the difference in water retention potential among RT, NT and CT systems.

Salem et al. (2015) showed that water potential under NT and RT systems at 20 and 40 cm depths were higher than the water potential under CT system. Higher water potential under RT and NT was ascribed by decreasing evaporation and increasing infiltration rate under conservative systems.

CONCLUSIONS

The effects of long-term (nine years) two conventional, three reduced and a no-till tillage practices on soil bulk density, macro, micro and total porosity and water retention were investigated.

The conservational tillage systems, reduced and no-till significantly increased bulk density, reduced macroporosity and plant available water content of a clayey soil under wheat, soybean-corn rotation in Mediterranean climate.

Macroporosity under reduced and no-till in some layers were lower than the critical value of 0.01 cm3 cm-3 which may negatively impact the crop yield due to the restriction of oxygen flux in rooting zone. Continuous loosening of surface soil by frequent tillage under conventional systems reduced bulk density and increased macroporosity compared to conservative systems.

Plant available water content under conven-tional tillage practices were higher compared to reduced and no-till practices, though crop residue on soil surface of conservative systems will reduce the evaporation under Mediterranean climate conditions and may provide more water than the increased water retention of conventional systems.

ACKNOWLEDGEMENTS

This research work was carried out with the financial contribution of the Scientific and Technological Council of Turkey (TUBITAK, Grant Number 115 O 353).

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