Sabit Ersahin

Macropore transport of bromide as influenced by soil structure differences

Macropore transport of chemicals in soil often causes unexpected contamination of groundwater. The effect of soil structure on the functions of various sized macropores was assessed, investigating transport of nonreactive bromide (Br) under matric heads of 0, � 2, � 5 and � 10 cm using undisturbed soil columns from A, Bw and E horizons of a Thatuna silt loam soil (fine-silty, mixed, mesic Xeric Argialbolls). The experimental breakthrough curves (BTC) for Br were described with a two-region physical nonequilibrium model. Greatest macroporosity occurred in the A horizon and lowest in the E horizon. The measured pore water velocity m under saturated conditions ranged from 18.92 cm day � 1 in the E horizon to 64.28 cm day � 1 in the A horizon. While the greatest dispersivity k occurred in the Bw horizon due to medium subangular blocky and prizmatic aggregates, the lowest dispersivity occurred in the E horizon due to its low macroporosity and massive structure. The fitted mobile water partitioning coefficient b ranged from 0.30 in the A horizon under 0 cm matric head to 0.93 in the E horizon under 0 cm matric head. The calculated values of rate of diffusive mass exchange a decreased with decreasing matric head in A and Bw horizons, and slightly increased and then decreased in the E horizon. The difference among each of the values of the parameters m, b, a and k for the A, Bw and E horizons was greatest under saturated conditions. However, gradually decreasing matric head until about � 3 cm decreased the difference among the values for a particular parameter for different horizons, sharply. The difference remained fairly unchanged with further decreases in the matric head, suggesting that most of the variability in macropore transport of bromide for these horizons caused by pores with radii larger than about 0.5 mm. In A and Bw horizons, there was a sudden change in soil solution movement between � 2 and � 5 cm matric head, indicating that macropore flow generally occurred at matric heads greater than

Spatial variability of soil physical properties as affected by different tillage systems

Abstract Penetration resistance (PR), soil bulk density (BD), and volumetric water content (VWC) are important determinants of crop production. The objectives of this study were to: (1) evaluate the effect of conventional (S1), conservation (S2), and reduced tillage (S3) systems on BD, PR, and VWC shortly after soil tillage; and (2) characterise the spatial variations of these soil properties before the seedbed preparation for the second crop in Taşliçiftlik clay loam (medium, mixed, mesic Ustic Fluvents) located in north‐central Anatolia, Turkey. Tillage effect was evaluated at two different soil depths (0–10 cm and 10–20 cm). Soil BD and VWC measurements were conducted on undisturbed soil samples and PR was measured with a hand‐pushing penetrometer. All three tillage systems increased the variation in the PR; S1 and S3 decreased and S2 increased the variation in BD; and S2 and S3 increased, and S1 decreased the variation in soil VWC in 0–10 cm depth. Spatial structure of PR in 0–10 cm was not affected by the tillage systems. Slight changes occurred in spatial structure of PR in 10–20 cm after the tillage. Spatial structure of BD in 0–10cm was considerably affected by S1 compared to both S2 and S3. In 10–20 cm depth, chiseling considerably altered the BD as indicated by semivariograms. However, tillage effect on BD was negligible in S1 and S3 in the same depth. Although the spatial structure of VWC in 0–10 cm depth was highly altered in S1, S2 and S3 had smaller effects on VWC in 0–10cm. Both S1 and S3 resulted in more uniform volumetric water content in 10–20 cm depth.

Use of Chromameter-Measured Color Parameters in Estimating Color-Related Soil Variables

Abstract Soil color is a soil property that may be used as an interpreting index in estimating processes and properties. Quantifying color allows one to obtain information for rapidly estimating the related processes in soils. CIELAB color parameters L*, a*, and b* of ground (air‐dried and sieved) soil samples and aggregate surfaces of four soil profiles formed in calcareous colluviums in northern Turkey were analyzed. Values of color parameters measured in ground and intact soils were compared and related to soil properties by the regression technique. Results revealed that the L* value obtained with a ground soil sample was a significant predictor of organic matter in A horizons (p < 0.001). Although calcic horizons yielded the highest L* values, no significant relationship was obtained between calcium carbonate contents and lightness of soils in any of horizons studied. The parameters of b* could adequately be used to quantify dithionite‐extractable iron oxide contents in soils studied. The results further showed that the CIELAB color parameters obtained with ground samples were more informative than that of aggrevated samples in relating color parameters to soil properties.

Soil, water and crop management practices in the dryland farming regions of Turkey

Turkey is experiencing pressure to increase crop production per unit area to achieve self-reliance in food supply. The main production concern before 1970 was to increase crop yields to meet the national consumption of an ever-increasing population. During this time the countrys capability to produce wheat was insufficient to meet the national demand. After the initiation of the National Wheat Research and Extension Project in 1969 the objectives of wheat production methods were changed to achieve not only higher but more economical yields per unit area. As a result the total area sown to wheat increased by only 9% between 1969 and 1990, whereas yields and total production increased 75 and 90%, respectively. This was due to developing or importing high-yielding varieties adapted to dry areas, increasing use of fertilizers and plant protection chemicals, and timely use of proper tillage made possible with modem equipment. Transferring research results to farmers and exchanging information with international scientists led Turkish scientists to establish the new goal of developing ecologically sound farming systems that could achieve higher, more economical yields per unit area. The key to this approach is to maintain or increase soil organic matter.