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摘要
In the and Southeast Anatolia Project (GAP) region of Turkey, crop yields are mainly limited by available water. A field experiment was conducted for wheat (Triticum durum L.) during the period 1993-1996 to evaluate the effects of deficit irrigation on yield and water use efficiency. Two line-source sprinkler laterals were used in order to create gradually varying deficit irrigation treatments (I-1 through I-5) with the two fixed irrigation intervals of 7-day (IF1) and 14-day (IF2). Irrigation water was applied based on cumulative Class-A Pan evaporation for the irrigation interval of 7-day (IF1I1); and to replenish soil water deficit in the 90 cm depth to the field capacity for the 14-day irrigation interval in treatment plots adjacent to sprinkler lateral (IF2I1).
The results revealed that grain yield response to irrigation varied considerably due to differences in soil water contents and winter rainfall distribution in the experimental years. Highest average grain yields were attained from the highest irrigation level (I-1) with 7-day interval in 1994, 1995 and 1996 as 8340, 6720, and 8070 kg/ha, respectively. The corresponding yield values for the 14-day treatment plots were 7720, 7130, and 7600 kg/ha. Yields of the least watered treatment (I-5) varied with seasonal rainfall and its distribution. Grain yields decreased with increasing distance from the line-source in both irrigation intervals. Severe soil water deficits significantly decrease grain yield. The two irrigation intervals for the same water level resulted in similar yields. ET was largest in the treatment plots adjacent to the laterals (I-1). Seasonal water use increased with increasing irrigation levels. Soil water deficit significantly reduced ET, which mainly depends on irrigation amounts. Seasonal water use of wheat in I-1 treatment ranged from 571 to 721 mm in three experimental years. The crop coefficients (K-c) curves were developed for the different treatments using the reference ET and actual monthly ET values during the experimental years. K-c values ranged from 0.6 during initial stage to 1.35 at anthesis for the I1F1 irrigation treatment. Significant linear relationships (R-2 = 0.81) between water use and grain yield were obtained in each season. The highest dry matter yield was obtained from I-1 treatment plots in the experimental years. Yield response factor (k(y)), which is the slope of relative evapotranspiration deficit and relative yield reduction, for wheat was calculated as 1.01. Consistently higher values of harvest index (HI) were obtained from the I-1 treatment plots. HI decreased with decreasing irrigation water amount. The highest WUE averaging 14.2, 14.9 and 12.6 kg/ha/mm were obtained in IF1I2, IF2I4, and IF1I4 treatments, respectively in 1993/1994, 1994/1995 and 1995/1996 growing seasons. Severe deficit irrigation treatment 15 in general resulted in minimum WUE in the experimental years.
- 出版日期2006-3-10
