Grain yield responses of barley and durum wheat to split nitrogen applications under rainfed conditions in a mediterranean environment

Abstract

Four experiments using split nitrogen applications to barley and durum wheat were grown in northern Syria in 1981/82 and 1982/83. The variables studied were nitrogen rate, ratio of splitting (percent at sowing/percent at tillering), and variety.

The ratio of splitting the nitrogen application influenced the shape of the grain yield response. In two of the experiments less nitrogen was required to achieve maximum yield where all the nitrogen was applied at the tillering stage. As the proportion of the total nitrogen applied at sowing was increased, the amount required to achieve the maximum yield also increased.

In one experiment where three barley varieties were compared, their yield responses to applied nitrogen varied from significantly positive, to significantly negative, depending on the ratio of application. Where all the nitrogen was applied at tillering no variety was responsive, but where all the nitrogen was applied at sowing one variety responded positively and another negatively.

The percentage of vitreous kernels in durum wheat, an important determinant of price, was influenced by the ratio of nitrogen application in one experiment. More nitrogen was required to reach a given percentage of vitreous kernels as the proportion of nitrogen applied at tillering was increased.

Possible practical implications for nitrogen application strategies for rainfed cereals in relation to soil nitrogen at sowing and rainfall distribution are discussed.