Determination of water requirement and the effect of the changes on some quantitative and qualitative characteristics of products of sugar beet

To determine sugar beet water requirement and the effect of changing the quantity of applied water on some production components, a study was carried out in Ekbatan Agricultural Research Station of Hamedān, Iran in four years (1994-1997) during which optimum water requirement, root and sugar yield, water use efficiency on the basis of root yield, sugar percentage and water use efficiency on the basis of sugar yield under no water and nutrients limitation conditions were measured and compared by water balance method for four growth periods of 130, 134, 152 and 162 days. At the same time, the water requirement of reference crop - poa - was measured by lysimeter in order to study the pattern of the variations of sugar beet crop coefficient. It was found that the amount of applied water for sugar beet was 8427, 7328, 10256 and 9026 m3.ha-1 in the four studied years, respectively with the average amount of 8759 m3.ha-1. Average four-year maximum crop coefficient was 1.04 at mid-growing season and the minimum one was 0.42 at early-growing season. The highest root yield, sugar yield and sugar percentage was obtained from 162-day growth period (116.8 t.ha-1, 20.36 t.ha-1 and 17.43%, respectively). The lowest ones were obtained from 130-day growth period (52.21 t.ha-1, 8.5 t.ha-1 and 16.26%, respectively). Results revealed that in 130-day growth period, root yield decreased and meanwhile, water use efficiency on the basis root yield and sugar yield was decreased to 7.1 and 1.2 kg.m-3 applied water, respectively. In the longer growth period, water use efficiency on the basis of root yield and sugar yield was 11.4 and 2 kg.m-3 applied water, respectively.