Ali Osman Demir

Optimizing levels of water and nitrogen applied through drip irrigation for yield, quality, and water productivity of processing tomato (Lycopersicon esculentum Mill.)

The main goal of this study was to evaluate the effects of different levels of irrigation water and nitrogen on yield, quality, and water productivity of processing tomato grown in clay-loam soil. Three water levels of pan evaporation (Epan) replenishment applied via drip irrigation (1.00 × Epan, 0.75 × Epan, and 0.50 × Epan) and four N application rates with fertigation (0, 60, 120, and 180 kg N·ha−1) were tested in the sub-humid climate conditions of Turkey during the 2010 and 2011 growing seasons. The highest marketable yields were observed with full irrigation (1.00 × Epan) for each season. Decreasing irrigation rate generally improved dry matter, total soluble solids, total sugars, titratable acidity, lycopene and total carotene, and decreased fruit NO3-N content and fruit total protein content slightly. The highest water productivity was obtained with a moderate soil water deficit (0.75 × Epan). The 180 kg N·ha−1 fertilization rate produced the highest values for marketable yield, fruit size, total soluble solids yield, NO3-N, and total protein content. Increasing N rate also increased the values of fruit total sugars and titratable acidity. Increasing both irrigation and N levels increased the NO3-N and protein contents. The higher lycopene and total carotene values were obtained in the treatments of 60 and 120 kg N·ha−1. Increasing N supply improved the water productivity with the 3 irrigation application ratios. Considering the quantity and quality for the processing and water productivity, the 0.75 × Epan irrigation regime and a 120 or 180 kg·ha−1 nitrogen supply can considered optimal.

Effect of different concentrations of diluted seawater on yield and quality of lettuce

This study was carried out to investigate the effects of irrigating lettuce (Lactuca sativa L. cv. Funly) with different concentrations of diluted seawater (0%, 2.5%, 5%, 10%, 15%, 20%) on the fresh yield, marketable yield and quality (DM, total soluble solids, titratable acidity, total sugar, vitamin C, NO3-N, protein, and total oxalate content). The experiments were conducted in a greenhouse in the autumn of 2012. The fresh yield, marketable yield, and DM of lettuce irrigated with 2.5% and 5% seawater were similar to those of control, but these parameters decreased in response to 10% seawater, and the lowest values were obtained in response to 20% seawater. The 2.5% seawater treatment had no effect on the vitamin C and NO3-N content, but both significantly decreased when lettuce was irrigated with seawater concentrations higher than 2.5%. Total soluble solids, total sugar, and protein content significantly increased in response to low salinity (2.5% and 5%) but decreased in response to increasing seawater stress. The titratable acidity values remained unchanged under the various saline conditions. Irrigation with diluted seawater did not affect the total oxalate content up to a concentration of 5%, but increasing the concentration of seawater above 5% increased oxalate content. The results of this study demonstrated that low concentrations of seawater are suitable for lettuce production and lettuce can be grown successfully using diluted seawater at concentrations of 2.5% and 5%.

The Hydraulic and Economic Performance Analysis of On-Demand Pressurized Irrigation Systems: A Case Study in Turkey

In this study, COPAM (Combined Optimization and Performance Analysis Model) software revealing optimum design possibilities and performance analysis of pressurized irrigation systems, was applied to on-demand pressurized irrigation system in Uludag University Agricultural Application and Research Centre, Bursa, Turkey. The system reliability, hydrant pressure heads, upstream elevation, discharges and pipe diameters related to this irrigation system were analyzed with COPAM software which have a variety of analysis tools. Analysis results showed that there were no deficiencies of performance in the hydrant level of the examined system. Furthermore, pipe diameters of the existing irrigation network were recalculated.

Economic Return versus Crop Water Productivity of Watermelon under Full and Deficit Irrigation Conditions

Field research was carried out in a sub humid climate at the Uludag University, Bursa, Turkey. Using the yield data obtained from the field research for 2011 and 2012, a partial economic analysis was conducted for watermelon (Citrullus vulgaris, var. Crimson Sweet) at four drip irrigation treatments of full irrigation [FI, 100% evapotranspiration (ETc)] and deficit irrigation (DI) [75% FI, 50% FI and 25% FI] and then compared to both physical and economic water use efficiency (WUE). Total costs and net incomes differed among irrigation strategies. Marketable yield (MY) and net income to land decreased with decreases in the amount of irrigation. The highest MY and net income to land were obtained with the full irrigation treatment. The results showed that full irrigation is recommended under non-water-limiting environments for higher yield and net income. The highest net income to water, physical WUE and economic WUE values were resulted from the 75% FI. With consideration to net income and water use efficiency, deficit irrigation management strategy of 75% FI under water-limiting conditions can be preferable, because it achieved irrigation water savings of 25%, an increase of 9% in crop water use efficiency and an acceptable net income with a yield loss of only approximately 8% compared with full irrigation.