Tahsin Tonkaz

The effects of different drip irrigation regimes on watermelon [Citrullus lanatus (Thunb.)] yield and yield components under semi-arid climatic conditions

This study was conducted to investigate the effects of drip irrigation on yield and yield components of watermelon [Citrullus lanatus (Thunb.) Crimson Tide F1] under semiarid conditions in the Southeastern Anatolian Project Region, Harran Plain, Şanliurfa, Turkey, during 2002 and 2003. Using a 4-day irrigation period, 4 different irrigation regimes were applied as ratios of irrigation water/cumulative pan evaporation (IW/CPE): 1.25 (I125), 1.00 (I100), 0.75 (I75), and 0.50 (I50). Seasonal crop evapotranspiration (ETc) rates were 720, 677, 554, and 449 mm in the first year and 677, 617, 519, and 417 mm in the second year for irrigation treatments I125, I100, I75, and I50, respectively. Amounts of irrigation water applied to the 4 respective treatments were 764, 642, 520, and 398 mm in 2002 and 709, 591, 473, and 355 mm in 2003. Maximum yield was obtained from I125, with 84.1 t/ha in 2002 and 88.6 t/ha in 2003. Yield was reduced significantly as the irrigation water was reduced. The values of water use efficiency ranged from 9.6 to 11.7 kg/m3 in 2002 and 10.8 to 13.1 kg/m3 in 2003. The unstressed I125 treatment produced 10.1 kg marketable watermelons/m3 irrigation in 2002, and 11.3 kg/m3 in 2003. By comparison, the least irrigated (I50) treatment produced 12.4 kg/m3 in 2002, and 14.9 kg/m3 in 2003. A yield response factor (ky) value of 1.15 was determined based on averages of 2 years, and watermelon was found to be sensitive to water stress. This result showed that yield loss (1 – Ya/Ym) is more important than evapotranspiration deficit (1 – ETa/ETm). The study demonstrates that 1.25 IW/CPE water applications by a drip system in a 4-day irrigation frequency might be optimal for watermelon grown in semi-arid regions similar to those in which the work was conducted.

The Effect of Water Stress on Some Morphological, Physiological, and Biochemical Characteristics and Bud Success on Apple and Quince Rootstocks

The effects of different water stress (control, medium, and severe) on some morphological, physiological, and biochemical characteristics and bud success of M9 apple and MA quince rootstocks were determined. The results showed that water stress significantly affected most morphological, physiological, and biochemical characteristics as well as budding success on the both rootstocks. The increasing water stress decreased the relative shoot length, diameter, and plant total fresh and dry weights. Leaf relative water content and chlorophyll index decreased while electrolyte leakage increased with the increase of water stress in both rootstocks. An increase in water stress also resulted in reduction in budding success in Vista Bella/M9 (79.33% and 46.67%) and Santa Maria/MA (70.33% and 15.33%) combinations. However, the water stress in Santa Maria/MA was more prominent. The increase in water stress resulted in higher peroxidase activities as well as phenol contents in both rootstocks. Although catalase activity, anthocyanin, and proline contents increased with the impact of stress, this was not statistically significant. The results suggest that the impact of stress increased with the increase of water stress; therefore, growers should be careful when using M9 and MA rootstocks in both nursery and orchards where water scarcity is present.

The effects of different irrigation regimes on yield and silage quality of corn under semi-arid conditions

The aim of this study was to evaluate the effects of different quantities of drip irrigation water on the corn yield and silage quality under semi-arid conditions. The seasonal evapotranspiration (ET c ) for the different irrigation regimes varied from 434 to 947 mm in 2004 and from 468 to 1003 mm in 2005 for total irrigation periods of 108 and 113 days, respectively. Combining data from both years, the relative evapotranspiration deficit (1−ET a /ET m ) for different regimes was 19 to 54% in corn compared to the maximum seasonal ET c when water was not limited in the (I 100 ) regime. During the course of both years, irrigation had an apparent effect on the total fresh silage yield (FSY), with yields increasing steadily from water stress to fully irrigated conditions, while silage yields increased linearly with the total depth of irrigation water applied between planting and harvest. Combining data from both years showed that the FSY was 35.0, 53.6, 83.3 and 88.9 t ha -1 for I 25 , I 50 , I 75 and I 100 , respectively. Moreover, the largest FSY recorded amongst these experiments at maximum seasonal yield in single treatment was 89.1 t ha -1 in 2004 and 88.7 t ha -1 in 2005. The water content decreased considerably in all but FSY, while the dry matters yield (DMY), organic matter (OM), acid detergent fiber yield (ADFY) and in vitro dry matter digestibility (IVDMD) increased. Furthermore, the study substantiated that the highest yield and silage quality were obtained at the full (I 100 ) irrigation regime. Key words: Silage, deficit irrigation, yield, silage quality.