Hikmet Günal

Spatial variability of depth and salinity of groundwater under irrigated ustifluvents in the Middle Black Sea Region of Turkey

Information on the potential risk for soil salinity buildup can be very helpful for soil salinity management in irrigated areas. We evaluated the spatial and temporal variability of groundwater salinity (GWS) and groundwater depth (GWD), which are two of the most important indicators of soil salinity, by indicator kriging technique in a large irrigated area in northern Turkey. GWS and GWD were measured on a monthly basis from irrigation season (August 2003) to rainy season (April 2004) at 60 observation wells in the 8,187-ha irrigated area. Five indicator thresholds were used for GWS and GWD. The semivariogram for each of the thresholds for both variables was analyzed then used together with experimental data to interpolate and map the corresponding conditional cumulative distribution functions (CCDF). Risk for soil salinity buildup was greater in the irrigation season compared to that in the rainy season. The greatest risk for soil salinity buildup occurred in the eastern part of the study area, suffering from poor drainage problem due to malfunctioning drainage infrastructure, as indicated by the CCDF of GWS and GWD obtained in both seasons. It was concluded that a combination of mechanical and cultural measures should be taken in high-risk locations to avoid further salinity problems.

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.

Assessment of wheel traffic effect on soil compaction using a soil core sampler

Abstract This study was conducted to evaluate the relative physical properties of soil samples collected with a manual sampling method and a tractor‐mounted portable soil core sampler under uncompacted and compacted soil conditions, and to determine the compaction depth resulting from successive passes of a tractor wheel. The compaction of soils was induced by one, three and five successive passes of the tractor wheel. The physical properties of soil samples obtained by both methods were similar at 10–15 cm soil depth. However, the methods produced significantly different results (P < 0.01) at 30–35 cm soil depth. Traffic applications resulted in a significant effect on both soil bulk density and hydraulic conductivity at both depths. The increasing number of passes resulted in increasing penetration resistance values at the depth of ploughing. In contrast, below the 25 cm depth, passes did not affect soil compaction compared to that at shallow depths. The results revealed that the portable sampler device could safely be used to collect soil cores. However, in clay soils having a high potential for compaction, the device needs to be supplemented by extra weight.

Higher Tolerance to Abiotic Stresses and Soil Types May Accelerate Common Ragweed (Ambrosia artemisiifolia) Invasion

Common ragweed is a troublesome allergenic invader and noxious weed of several crops. Despite extensive research to understand the factors affecting its invasion, the role of environmental stresses and soil types on survival and growth is poorly understood. The objective of this study was to determine the effects of drought, salinity, and soil types on survival, growth, and nutrient uptake of ragweed in greenhouse experiments to predict its invasiveness in Turkey. Three separate experiments, with five drought intensities (100, 75, 50, 25, and 12.5% of field capacity [FC]), four levels of salinity (0, 3, 6, and 12 dS m-1), and five soil types varying in sand, silt, and clay content were performed. Severe drought and salinity levels reduced seedling survival, while soil type had no effect. Increasing drought and salinity negatively affected growth and nutrient uptake; the poorest growth was observed under severe drought intensity. Ragweed exhibited intensive tolerance to drought, even severe levels, while it tolerated salinity up to 6 dS m-1 for seedling survival. Growth was negatively affected above 3 dS m 1. The highest and lowest nutrient accumulations were recorded under moderate and extreme drought intensities, respectively. Similarly, the highest Na accumulation was observed under extreme saline conditions, whereas the highest P uptake and K/Na ratio were achieved under nonsaline conditions (0 dS m-1). Variation of soil texture had no effect on growth and nutrient uptake. The highest Ca, Mg, and Na accumulations were recorded on clay soil, while higher P accrued on sandyloam soil. Increased tolerance of ragweed to severe drought and moderate salinity and its nonselective nature for soil type indicate that semiarid and partially arid regions in Turkey have plenty of vacant niches for ragweed invasion. Nomenclature: Ragweed, Ambrosia artemisiifolia L. AMBEL

Invasion Potential of Two Tropical Physalis Species in Arid and Semi-Arid Climates: Effect of Water-Salinity Stress and Soil Types on Growth and Fecundity.

Invasive plants are recognized for their impressive abilities to withstand adverse environmental conditions however, all invaders do not express the similar abilities. Therefore, survival, growth, nutrient uptake and fecundity of two co-occurring, invasive Physalis species were tested under water and salinity stresses, and different soil textures in the current study. Five different water stress levels (100, 75, 50, 25, and 12.5% pot water contents), four different soil salinity levels (0, 3, 6, and 12 dSm-1) and four different soil textures (67% clay, 50% clay, silt clay loam and sandy loam) were included in three different pot experiments. Both weeds survived under all levels of water stress except 12.5% water contents and on all soil types however, behaved differently under increasing salinity. The weeds responded similarly to salinity up till 3 dSm-1 whereas, P. philadelphica survived for longer time than P. angulata under remaining salinity regimes. Water and salinity stress hampered the growth and fecundity of both weeds while, soil textures had slight effect. Both weeds preferred clay textured soils for better growth and nutrient uptake however, interactive effect of weeds and soil textures was non-significant. P. angulata accumulated higher K and Na while P. philadelphica accrued more Ca and Mg as well as maintained better K/Na ratio. P. angulata accumulated more Na and P under salinity stress while, P. philadelphica accrued higher K and Mg, and maintained higher K/Na ratio. Collectively, highest nutrient accumulation was observed under stress free conditions and on clay textured soils. P. philadelphica exhibited higher reproductive output under all experimental conditions than P. angulata. It is predicted that P. philadelphica will be more problematic under optimal water supply and high salinity while P. angulata can better adapt water limited environments. The results indicate that both weeds have considerable potential to further expand their ranges in semi-arid regions of Turkey.

Germination Biology of Two Invasive Physalis Species and Implications for Their Management in Arid and Semi-arid Regions

Two Solanaceae invasive plant species (Physalis angulata L. and P. philadelphica Lam. var. immaculata Waterfall) infest several arable crops and natural habitats in Southeastern Anatolia region, Turkey. However, almost no information is available regarding germination biology of both species. We performed several experiments to infer the effects of environmental factors on seed germination and seedling emergence of different populations of both species collected from various locations with different elevations and habitat characteristics. Seed dormancy level of all populations was decreased with increasing age of the seeds. Seed dormancy of freshly harvested and aged seeds of all populations was effectively released by running tap water. Germination was slightly affected by photoperiods, which suggests that seeds are slightly photoblastic. All seeds germinated under wide range of temperature (15–40 °C), pH (4–10), osmotic potential (0 to −1.2 MPa) and salinity (0–400 mM sodium chloride) levels. The germination ability of both plant species under wide range of environmental conditions suggests further invasion potential towards non-infested areas in the country. Increasing seed burial depth significantly reduced the seedling emergence, and seeds buried below 4 cm of soil surface were unable to emerge. In arable lands, soil inversion to maximum depth of emergence (i.e., 6 cm) followed by conservational tillage could be utilized as a viable management option.

Clay mineralogy, specific surface area and micromorphology of polygenetic soils from Eastern Kansas

The objective of this study was to evaluate the relationship between clay mineralogy, specific surface area (SSA) and micromorphology in polygenetic Konza soil series. Physical, chemical and mineralogical analyses were performed on disturbed soil samples, and micromorphological investigations of selected horizons were done on undisturbed soil samples. X-ray diffraction indicated that lower part of each parent materials has more mectite and less clay mica content than that of the upper horizons in each parent material. Greater amounts of smectite can be attributed to transformation product of the clay mica in to smectite, eluviation from upper horizons or originated from parent material. Specific surface area of upper horizons in each parent material tended to increase to lower horizons. Clay content gradually increased from surface (21%) to the lower part (∼48%) of the solum. Clay in Bt horizons had strong birefrengent, sharp boundary, and strong orientation pattern. SSA, clay content increase, clay mineralogy and oriented clay features agreed to one another. Therefore, this relationship gives opportunity to make predictions on extend of SSA and related soil processes by looking at one of these features.

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

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 longterm (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.

The Influence of Environmental Factors on Germination of Burcucumber (Sicyos angulatus) Seeds: Implications for Range Expansion and Management

Abstract Burcucumber (Sicyos angulatus L.) is a highly invasive vine that has become naturalized in the humid Black Sea region of Turkey, but previous to this study there was no information on the germination biology of this weed. The germination biology of three naturalized populations of S. angulatus from the Black Sea region was studied in laboratory and greenhouse experiments. The germination of nondormant seeds was observed under different photoperiods, constant temperatures, and varying levels of pH, salinity, and osmotic potential. Furthermore, seedling emergence from various soil depths was investigated. The seeds of all populations proved nonphotoblastic (82% to 90%, 55% to 66%, and 48% to 56% germination under 12-, 24-, and 0-h photoperiod, respectively) and germinated over a wide range of temperatures (5 to 40 C). Seedlings emerged from all seed burial depths (0 to 15 cm); however, germination was drastically reduced (>90% reduction) beyond 6 to 8 cm. Seed germination was 30% to 38% for seeds placed on the surface and increased to 78% to 88% for seeds buried 2 cm deep, while germination was severely reduced for seeds buried 10 and 15 cm deep (8 to 12% and 0 to 6%, respectively). Seeds of all populations were found to be sensitive to osmotic and salinity stress and to highly acidic and alkaline pH levels. All populations had similar requirements for germination that are directly related to their area of naturalization. These results indicate that the species has limited potential for range expansion to arid, semiarid (nonirrigated), and relatively saline areas. However, humid, salinity-free, and frequently irrigated areas of the country are at high risk of invasion. In arable lands, deep tillage followed by shallow tillage and effective management of emerging seedlings could deplete the soil seedbank in the long run. However, there is an urgent need for effective strategies to manage the species in other nonarable areas.