Abstract:
A short term Neubauer experiment was conducted to evaluate the effect of cobalt on the growth as well as cobalt
uptake of barely (Giza 126 variety) grown in three alkaline soils from the north west coast of Egypt in relation
to AAAA-EDTA (Acetic Acid Ammonium Acetate-EDTA) extractable cobalt in the tested soils of the
uncropped treatments. Treatments of five levels of cobalt (0, 5, 10, 20, 40, 80, and 100 mg/kg soil) were
superimposed on the tested soils. The data indicated that the available cobalt concentration increased with
increasing cobalt application rate. The concentration of cobalt extracted with AAAA-EDTA increased
polynomialy in response to cobalt application for the three studied soils. The data showed also, that the effect of
cobalt application on the growth of barely plants was significant on the clay soil (Soil A) and insignificant on the
clay loam and sandy loam soils (Soils B and C). The higher dry matter yields were obtained with the application
of cobalt to the soils at the rate of 20 mg Co/Kg soil. The tolerance index (Ti) for the addition of 5 to 80 mg
Co/Kg soil (>1) shows a favourable effect for the growth of barley. Also, the tolerance index was varied with the
soil characteristics. Cobalt concentration or uptake by barley was increased significantly with cobalt application
and this was also evidenced by the increase in AAAA- EDTA extractable cobalt from the tested soils. The
average uptake values of cobalt followed the sequence order: soil C (sandy loam) >soil B (clay loam)> soil A
(clay). Also percentage utilization of added cobalt was highest in soil C followed by soil B and soil A. In
conclusion the application of cobalt in a low level improved growth of barely and may be applied to the soil at
the recommended rate in term of cobalt sulphate.
