Yield and quality response of drip irrigated green beans under full and deficit irrigation

The effects of different irrigation regimes on yield and quality of green beans (Phaselous vulgaris L.) irrigated with a drip irrigation system under field conditions in the Mediterranean region of Turkey were evaluated along two years. Irrigation regimes consisted of four irrigation intervals based on four levels of cumulative pan evaporation (Epan) values (I1: 15; I2: 30; I3: 45 and I4: 60 mm); irrigations occurred on the respective treatments when Epan reached target values, and three plant–pan coefficients as for irrigation levels (Kcp1 = 0.50, Kcp2 = 0.75 and Kcp3 = 1.00). Irrigation intervals varied from 2 to 4 days in I1, 5 to 7 days in I2, 8 to 10 days in I3 and 10 to 12 days in I4 treatments in 2004 and 2005 growing seasons Both irrigation levels and intervals significantly affected the green bean yields. Maximum and minimum yields were obtained from the I1Kcp3 and I4Kcp1 treatments as 24,320 and 14,200 kg ha−1 in the first, and 23,850 and 13,210 kg ha−1 in the second experimental year, respectively. As the Kcp value decreased the total yields in each irrigation interval also decreased. However, with the longer irrigation interval (I4), lower yields were obtained with all Kcp coefficients. Seasonal water use (ET) values in the treatments varied from 276 mm in I4Kcp1 to 400 mm in I1Kcp3 in the first experimental year, and from 365 mm in I4Kcp1 to 472 mm in I1Kcp3 in the second experimental year. Significant linear relations were found between green bean yield and seasonal ET for each experimental year. Irrigation intervals resulted in similar water use in the treatments with the same Kcp value. Water use efficiency (WUE) and irrigation water use efficiency (IWUE) values were significantly influenced by the irrigation intervals and plant–pan coefficients. WUE ranged from 4.33 kg m−3 in I4Kcp3 to 6.08 kg m−3 in I1Kcp3 in 2004, and varied from 3.62 kg m−3 in I4Kcp1 to 5.43 kg m−3 in I2Kcp2 in the 2005 growing season. Maximum IWUE was observed in I2Kcp1 (6.16 kg m−3), and minimum IWUE was in I4Kcp3 treatment (3.83 kg m−3) in the experimental years. Both irrigation levels and irrigation frequencies had significantly different effects on quality parameters such as fresh bean length, width, number of seed per pod and 100 fresh bean weights. In conclusion, I1Kcp3 irrigation regime is recommended for field grown green beans under the Mediterranean conditions in order to attain higher yields with improved quality.