The water requirement, water requirement rate and crop coefficient of alfalfa in Bashang area

The water requirement (WR) and water requirement rate (WRR) of alfalfa (Medicago sativa) were studied in Bashang area of Hebei Province with large scale noweightinglysimeter. The reference crop evapotranspiration(ETo) was calculated by the PenmanMonteith formula, and the crop coefficient（Kc）of alfalfa was determined on the measured WR and calculated ETo in the same period. The results showed that the WR of alfalfa during the first harvest, second harvest, third harvest and whole growth season(1st-3rd harvest) in 2008 were 157.8, 192.0, 199.5 and 549.3 mm, separately. The WR of first harvest was lower than that of the second and third harvest significantly(P＜0.05),and the WR of second and third harvest was not significantly different. The WRR were 2.6, 6.2, 4.2 and 3.9 mm/d, separately. The WRR of second harvest was higher than that of the first and third harvest significantly (P＜0.05), and the WRR of third harvest was higher than that of the first harvest significantly (P＜0.05).The Kc were 0.61, 1.34, 1.30 and 0.99,separately.The Kc of the second and third harvest were higher than that of the first harvest evidently, and they were more than 2 times to the later.