A study was conducted for two growing seasons in northeastern Syria to evaluate the effect of N and P fertilizers and previous crops--i.e. vetch (Vicia sativa L.), barley (Hordeum vulgare L. cv. Beecher) or fallow--on water consumption, development, growth and yields of barley in a semi-arid, Mediterranean-type climate. / The two seasons contrasted in rainfall and temperature which affected soil N, water use and yields. Fertilizer addition and residual P were the major determinants in barley yield increases. Rotation effects were significant only when fertilizers were added. Fallowing was an inefficient way of storing water, but stored water was used most efficiently by subsequent barley crops when fertilized. / Fertilizers did not increase total evapotranspiration. Water use efficiency was related to dry matter production at stem elongation (DMse). Grain weight was a stable component of grain yields. Grain number was related to crop growth rates during the three week pre-anthesis period and to DMse, in turn affected by temperature, nutrient and moisture conditions. / Vetch yields were in the order of 2.5 t.ha$ sp{-1}$ in the wetter season (1982/83). / Results showed that substantial barley yield increases can be obtained with innovative crop rotations and appropriate use of fertilizers in semi-arid environments.

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