ChileanJAR

Yields and efficiency of water are presentad in two factorial trials on rain fed wheat sown in 1983 and 1984 in the coastal range of chilean VI Region where climate is marine-mediterranean and soils are mainly clayey. During the growing period rainlall was 690 mm in 1983 and 1.113 mm in 1984. Pan evaporation in the sama periods was 660 mm and 764 mm, respectively. The crop was healthy in 1983; in 1984 there were symptoms of Septoria sp in the short-cycle variety sown early and leavas showed generalizad yellowness. This yellowness seems to be relatad to excess of water during winter. Estimated dry malter yields were high, reaching a maximum of 17ton/ha in 1983 and near 19 ton/ha in 1984. The most important effect was that of nitrogen which increased yields in about 5 ton/ha of dry malter in the short-cycle variety seeded at normal date in 1983. Grain yields in the N treatments were 5-6 ton/ha, when potential yields in that area are 7-8 ton. This shows the presence of sorne limitations in both years. In 1983 the decrease in yield in relation to potential yield in the region showed a good relation with the deficit of evapotranspiration (Et_a/ET_m) thus indicating that in 1983 the limiting factor was water delicit. However in 1984 yield decrease in relation to potential yield was bigger than expected according to the aforementioned relationship, which indicate that a different limiting factor was acting. Observations most probably show that the limiting factor in 1984 was Septoría sp and excess of water in winter. Efficiency al supplied water in springtime (initial water plus rainfall) in 1983 was 894 L of water/kg of grain as average of treatments without N, and 701 L of water/kg of grain in those with N. In 1984 the ligures were 1.524 and 1.289 L/kg, respectively. In the whole cropping period, elliciency al evapotranspirated water was estimated in 1983 in 547 L/kg of grain as average of treatment without N and 444 L/kg of grain in those