Harun Kaman

Seasonal changes of spatial variation of some groundwater quality variables in a large irrigated coastal Mediterranean region of Turkey

Soil and groundwater degradations have taken considerable attention, recently. We studied spatial and temporal variations of groundwater table depth and contours, and groundwater pH, electrical conductivity (EC), and nitrate (NO3) content in a large irrigated area in Western Mediterranean region of Turkey. These variables were monitored during 2009 and 2010 in previously constructed 220 monitoring wells. We analyzed the data by geostatistical techniques and GIS. Spatial variation of groundwater table depth (GTD) and groundwater table contours (GTC) remained similar across the four sampling campaigns. The values for groundwater NO3 content, EC, and pH values ranged from 0.01 to 454.1 gL(-1), 0.06 to 46.0 dS m(-1) and 6.53-9.91, respectively. Greatest geostatistical range (16,964 m) occurred for GTC and minimum (960 m) for groundwater EC. Groundwater NO3 concentrations varied both spatially and temporally. Temporal changes in spatial pattern of NO3 indicated that land use and farming practices influenced spatial and temporal variation of groundwater NO3. Several hot spots occurred for groundwater NO3 content and EC. These localities should be monitored more frequently and land management practices should be adjusted to avoid soil and groundwater degradation. The results may have important implications for areas with similar soil, land use, and climate conditions across the Mediterranean region.

RESPONSE OF MAIZE TO PARTIAL-ROOT-DRYING IRRIGATION

The new irrigation techniques with higher water application efficiency should replace the commonly used traditional methods of irrigation in order to increase agricultural production for compensating the decrease of land and water resources, largely allocated to municipal and industrial usage. To this effect, a new innovation for deficit irrigation, called “partial root-drying” (PRD) practice, is promoted in recent years. In PRD technique, irrigation water quantity applied normally under the traditional irrigation practices is reduced in a certain portion, wetting only halves of plant roots and leaving other halves dry. In the following irrigation, the other halves get wet. In this way, the aim is to use limited water resources more efficiently; similar to what is achieved with the traditional deficit irrigation practices (Kang et al., 1998). In the PRD technique, while halves of the plant roots were wetted, the other halves were relatively left dry. According to PRD practices, plant roots were divided into two parts and each was grown in separate pots. Plants could keep growing while watering only one of the pots, and leaving the other dry. Under such cases, stomas are relatively closed and thus evapotranspiration reduces (Zhang et al., 1987; Davies and Zhang, 1991). It was suggested that the closure of stomas when halves of the roots were exposed to drought is controlled via chemical signals transferred from roots to the leaves (Davies and Zhang, 1991; Tardieu and Davies, 1992). While these signals reduce vegetative growth of the plant, they stimulate generative growth. In the case of wetting only halves of the roots and leaving the other halves dry, the abscisic acid concentration in xylem elements increases and causes stomatal closure (Stoll et al., 2000). The change in root water potential and rise of pH in xylem were other signals shown to be effective in controlling stomatal closure in leaves (Wilkinson and Davies, 1997). In numerous studies reported on the field-PRD-irrigation technique, only one species of plant was used. Different responses of plant species to different deficit irrigation practices were not focused on. Although Kang et al. (2000) and Kirda et al. (2005) used the same plant species in their work, their reported maize-crop-yield results obtained using PRD irrigation were different possibly due to the different climatic and soil characteristics. In this study, the response of five different maize species were studied under the traditional deficit and PRD irrigation technique, to investigate the hypothesis that maize crop yield response to different modes of deficit irrigation (i.e., DI or PRD) may genetically be controlled. Partial results such as yield, irrigation water-use Pak. J. Agri. Sci., Vol. 54(1), 209-216; 2017 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/17.3938 http://www.pakjas.com.pk

SPATIAL AND TEMPORAL EVALUATION OF DEPTH AND SALINITY OF THE GROUNDWATER IN A LARGE IRRIGATED AREA IN SOUTHERN TURKEY

It is of high importance to monitor groundwater level and salinity in wide irrigated farming lands. This is because high levels of groundwater and salinity in irrigated lands are major constraints for sustainable agriculture. Thus, this work undertaken aims at monitoring spatial and temporal changes of groundwater level and salinity in irrigated large farm lands. The research work was implemented in Akarsu Irrigation District (Akarsu ID) which is located in Southern Turkey, Lower Seyhan Plain (LSP) in 2007 hydrologic year. During 2007 hydrologic year, depths to water levels in groundwater wells (m) and groundwater salinity, as electrical conductivity (EC, dS m -1 ) were measured through five-month-period; from January to October. The results of depth (m) and salinity analysis (dS m -1 ) of the groundwater wells were mapped using geographical information system. In addition, cropping pattern and crop water requirements of the study area were specified. The results showed that groundwater reached to a critical threshold level in February because of heavy rains. It was noted that there were not any drainage problems in May. In July, however, the drainage problem was the worst. On the other hand, average groundwater salinity levels were higher in May, in early irrigation season, than July and October. The areas in which groundwater salinity was higher than the critical level (i.e., EC > 5 dS m -1 ) covered 19.2% of the total area in May, 17.7% in July, and 15.5% in September. During the study period, irrigation efficiency was indeed very low, 33.4%. Depending on the research findings, the drainage problem was

Salt Accumulation in the Root Zone of Eggplant Irrigated using Partial Root Drying Technique

In this study, the yield and possible salt accumulation around the root area of eggplant was investigated. Seven irrigation treatments were tested including a controlling irrigation (FULL). Two of these irrigation treatments had 25% and 50% less water accordingly than the treatment of FULL and water was conventionally applied to both sides of the plant roots (CDI25 and CDI50). The other two deficit irrigation treatments had 25% and 50% less water accordingly than the treatment of FULL and water was applied only one side of the roots and the other halves were left relatively dry in each irrigation. This case was replaced alternatively for every irrigation (APRD25 and APRD50). The last two deficit irrigation treatments had also 25% and 50% less water accordingly than the treatment of FULL, however throughout the season water was applied only one side of the roots and the other halves were left relatively dry in each irrigation in fixed irrigations (FPRD25 and FPRD50). The differences between the yields of the eggplant under different irrigation treatments were statically important (p < 0.01). The range of yields depending on irrigation treatments were between 23.37 t ha and 83.10 t ha. The highest salt accumulation was recorded in treatment FPRD25 for the root area and treatment CDI50 for along the rows of plants. When compared with the values of the beginning of the season; the salinity was multiplied by 3.2 for the root area of treatment FPRD25 at the end of the season. In a similar way, the salinity was multiplied by 7.1 at the end of the season for treatment CDI50 along the rows of plants when compared with the beginning of the season.