Difference of water use efficiency and water consumption coefficient of alfalfa different in growing season

Difference of water use efficiency (WUE) and water consumption coefficient (WCC) of alfalfa (Medicago sativa) between the first growing season and the second growing season was studied in Beijing plain with microlysimeter. The results showed that the WUE based on biological and economic yields 14.7 and 17.1 kg/(hm2mm) of the second growing season were significantly (P0.05) higher than that of the first growing season 12.6 and 14.7 kg/(hm2mm), the WCC based on biological yield and economic yield（679 and 584）of the second growing season were significantly (P0.05) lower than that of the first growing season (793 and 682). This proved that the growing years affected the WUE and WCC.