Grain yield and nitrogen uptake by barley subjected to fertilization and water regimes using 15N stable isotope

الملخص EN

A lysimeter experiment was constructed to evaluate the acquisition of nitrogen fertilizer applied in different rates and splitting doses (mode) by barley crop grown on sand soil under different irrigation water regime.

Every lysimeter was backed with 90 kg of experimental sand soil.

Fertilizer nitrogen as ammonium sulfate form enriched with 2% 15N atom excess was applied at rates of 120% (equal to 187.2 kg N ha-1 or 10.51 g N lys-1), 100% (equal to 156 kg N ha-1 or 8.76 g N lys-1) and 80% (equal to 124.8 kg N ha-1 or 7 g N lys-1) of the recommended rate (65 kg N fed-1).

Nitrogen fertilizer rates were splitted into three modes of application as following: 33, 33, 33%; 40%, 30%, 30% and 50%, 25%, 25%.

Three irrigation regimes: 60%, 80% and 100% of crop evapotranspiration (ETc).

Irrigation with W2 regime combined with either N2 or N3 fertilizer rates applied at S3 splitting doses resulted in a higher grain yield than other treatments.

Water regime W1 interacted with either N1 or N2 achieved the best values of N uptake by grains.

The grand mean of N uptake by grains as affected by application modes pointed out no significant difference between them.

Generally, growth and nitrogen fertilizer uptake by barley grains were enhanced by N1 (187.2 kg N ha-1) rate applied in splitting doses S3 (50, 25, 25) under 100% ETC water regime (W1).

Combined treatment of W1xN2xS3 was the best where it gave remarkable Ndff values gained by grains as indicated by overall means of the tested factors.

The best %NUE by grains occurred with combined treatment of W1 x N1 x S3 achieving 67%.

Fertilizer-N remained in the soil after harvest was not affected by water regime or splitting modes whereas it increased with the lowest N rate (N3) as compared to other nitrogen fertilizer rates