Berseem (Trifolium alexandrinum L.), a common forage crop in India, requires frequent irrigation to maintain its productivity in ditl'erent seasons. It is very sensitive to the soil-moisture regime. Yield and the length of growing period are greatly affected'by irrigation. Shukla'and Menhi L~(1988, 1993\studied the effect of irrigation methods and moisture regime on the water-use efficiency ofberseem. Prediction of evapo-transpiration (ET) as a function of crop stage is important for determining crop-water-use and sched-mjng Hrig. atioo. The water sJress jn the pJlIDl can be qlJ3nlj-tied by actual evapo-transpiration rate; as the level of evapotransipiration is related to the evaporative demand of the air (Doorenbos anu Kassam 1979). Evapo-transpiration loss and rate of evapo-transpiration at ditferent cuttings indicate the amount of water required at difl'erent growth periods for its satisfactory growth and optimum production. Menhi Lal and Shukla (1985, 1988) reported evapo, transpiration and water-use efficiency (WUE) pattern in'MP Chari'oat (Avena sativa L.) in relation to growth stag~ s and meteorological conditions. However, only a few measurements of evapotranspiration of berseem are available (Gaillard et al. 1977, Alvarez and Quiroga 1992). The present'investigation was taken up to study the crop evapo-transpi~ ation and peak period of water-use efficiency of berseem,. md establish the relationship between forage productivity and periodical evapo-transpiration.

A field experiment was conducted for 4 consecutive winter season (rab!) of 1991-92, 1992-93, 1993-94 and 1994-95 using 2 weighing Iysimeters of size 1.30 mx 1.30 mx 0.90 m at Jhans!. However, data of 1993-94 were not considered because the cutting period did not coincides with other years due to late sowing. The maximum capacity of weighing machine is 2 000 kg and the sensitivity of the system is±0.2 kg, which is equivalent to 0.12 mm of evapotranspiration or rainfall.