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Soil and Water Research Department, Isfahan Agricultural and Natural Resources Research and Education Center, AREEO, Esfahan, Iran.
Abstract:   (212 Views)
The large area of saline soils in Iran and decreasing in quality of these soils require that the effectiveness of conservation tillage systems in such lands be investigated. This project aims to determine changes in soil physical properties in three different types of tillage system and plant residue management, including: 1) conventional tillage system and removal of crop residues from soil surface, 2) reduced tillage system and preservation of crop residues, and 3) no tillage system and preservation of crop residues in rotation of barley and safflower in a saline soil with irrigation water salinity of 5.35 dS/m for four years. Some soil physical properties such as bulk density and porosity, and aggregate stability indices of mean weight diameter (MWD) and geometric mean diameter (GMD) were measured in soil samples prepared from the layers of 0-10, 10-20 and 20-30 cm. After each crop rotation period, water infiltration into the soil was measured and the modified Kostiakov model was fitted to obtain the optimized parameters. The results of variance analysis of the data in the four years of the experiment showed that the difference in most of the soil properties at the end of the experiment was significant due to the tillage treatments compared to the control. The highest MWD and GMD (2.53 and 1.90 mm, respectively), porosity (51.2%) and final infiltration rate (31 cm/h) were observed in the no-tillage system. while the lowest MWD and GMD (2.02 and 1.29 mm, respectively), porosity (47.8%) and final infiltration rate (3.5 cm/h) were recorded in the conventional tillage system. Overall, our findings showed that the increment in the soil organic matter due to the implementation of conservational tillage treatments improved the stability of soil aggregates and increased soil porosity and water infiltration into the soil.

Background and Objective: Presence of sodium in the salt-affected soils causes the dispersion and disintegration of clay particles, which leads to the destruction of the soil structure and, as a result, poor aeration of the root growth environment and the reduction of root penetration and water storage in the soil. The binding of clay particles and maintaining the soil structure strongly depend on the soil salinity and sodicity, the soil organic matter content, the rate of wetting and the type of soil clays (2). Tillage practices could reduce the soil bulk density in the plow layer, which gradually returns to its initial level upon consolidation due to natural processes. These changes depend on the type of soil and tillage tools (3). Hajabbasi et al. (4) studied the effects of different tillage methods on the MWD in Kabutarabad, Isfahan. In no-tillage treatment, the MWD was 20% higher than in other treatments. Water infiltration and microporosity in two soil types (i.e., silty loam and sandy loam) were significantly lower in the conventional tillage than in no-tillage, while no significant difference was observed for the macroporosity (1).

Methods: The current research was carried out at Kabutarabad agricultural research station, located in the southeast of Isfahan city, in fixed plots of the conservation agriculture experimental site for four years in split plots design. The main plots included three different types of tillage system and crop residue management, including: 1) conventional tillage and removal of residues from the field, 2) reduced tillage and preservation of residues, and 3) no tillage and preservation of residues. Soil layers of 0-10, 10-20 and 20-30 cm were considered as sub-plots. At the time of harvesting of each crop, soil samples were prepared from the three layers and physical properties were measured in the laboratory. After harvesting, the water infiltration into the soil was measured by the double rings method. The soil texture (i.e., percentages of sand, silt and clay) was determined by hydrometric method. Soil bulk density was determined by the core samples collected by using cylinders of 100 cm3. Wet and dry sieving methods were used to measure the aggregate stability and mean weight diameter (MWD) and geometric mean diameter (GMD) of the aggregates were calculated.

Results: Soil porosity was observed in the order of: no tillage > reduced tillage > conventional tillage and their values were 51.2, 50.4 and 47.8%, respectively. The highest soil porosity (i.e., 54.1%) was recorded in the no-tillage at the layer 10-20 cm and the lowest value (i.e., 47.9%) occurred at the layer 0-10 cm in the conventional tillage. The effects of tillage treatment, as well as the interaction effect of these treatments and the soil layer on the bulk density were not significant. The highest MWD and GMD (2.53 and 1.90 mm, respectively) were observed in the no-tillage, while the lowest values (2.02 and 1.29 mm, respectively) were recorded in the conventional tillage. In four years of the experiment, plots with conventional tillage had the lowest water infiltration rate.

Conclusions: Four years of research in saline soil showed that the reduced tillage and especially no tillage significantly increased soil porosity, infiltration rate and stability of soil aggregates. The increment in soil organic matter and lowered machinery traffic are the most important reasons for these positive effects. These effects became larger over time so that the most positive effect was observed in the fourth year of experiment.

1. Azooz, R.H., Arshad, M.A., Franzluebbers, A.J., 1996. Pore size distribution and hydraulic conductivity affected by tillage in Northwestern Canada. Soil Science Society of America Journal 60(4): 11971201.
2. Barzegar, A., 1995. Structural Stability and Mechanical Strength of Salt-affected Soils. PhD Thesis, Adelaide University, Australia.
3. Green, T.R., Ahuja, L.R., Benjamin, J.G., 2003. Advances and challenges in predicting agricultural management effects on soil hydraulic properties. Geoderma 116(1-2): 327.
4. Hajabbasi, M.A, Mirlohi, A.F., Sadrarhami, M., 1999. Tillage effects on some physical properties of soil and maize yield in Lavark research farm. Journal of Water and Soil Sciences 3(3): 1324. (In Persian with English abstract)

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Type of Study: Research | Subject: Physical and chemical processes in the rhizosphere
Received: 2023/02/17 | Accepted: 2023/03/30 | Published: 2023/06/18

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