Growth of Calamagrostis brachytricha Steud. and Festuca glauca Lam. and estimated water savings under evapotranspiration-based deficit irrigation.

摘要

Calamagrostis brachytricha Steud. (feather reed grass) and Festuca glauca Lam. (blue fescue) were grown in mini-lysimeters under four irrigation regimes based on maximum crop evapotranspiration [ET_c; 100% ET_c (control)], 75% ET_c, 50% ET_c, or 25% ET_c in order to estimate potential water savings in landscape management. Plant responses showed that shoot width, the number of tillers, and shoot dry weights (DWs) in feather reed grass were affected by deficit irrigation, and that there were significant linear correlations between these measurements and irrigation regime. However, in 2006, none of these parameters showed any significant difference between 75% ET_c irrigation and the 100% ET_c control. In 2007, plant height and the number of tillers gave similar results. There were significant linear correlations between irrigation regime and shoot height, shoot width, and shoot DW in blue fescue plants in 2006 and in 2007, while plants irrigated at 75% ET_c showed no significant differences from control 100% ET_c plants in both years. To save water and ensure high aesthetic value, a 75% ET_c irrigation regime is recommended for both species. Crop coefficients (K_c) were calculated for both species in order to estimate the supplementary irrigation required under historical average conditions (between 1841-1993). Based on these K_c values, historical reference evapotranspiration, and average precipitation, the model indicated that both species required supplementary irrigation during May, June, September, and October. Annual supplementary irrigation was 349.1 mm for feather reed grass and 163.3 mm for blue fescue at 100% ET_c. Neither feather reed grass nor blue fescue required supplementary irrigation in July and August, which accounted for 62.4% of annual precipitation. Deficit irrigation at 75% ET_c would save 33.1% and 40.3% of annual water use for feather reed grass and blue fescue, respectively.