The ammonium (NH4) and nitrate (NO3) are the available nitrogen (N) forms that plants need in large quantities.
Their existence in the soil is limited, and concentrations are kept low due to the losses by leaching in the soil
profile and microbial consumptions. Sustainability of the plant available nitrogen forms in soil profile is
important for plant growth and crop production. In this research, our main objective was to evaluate mineral
nitrogen (Nmin) status of the first crop corn soils and plants in Akarsu Irrigation District of Cukurova Region in
2007. Soil samples prior to sowing and after harvest were taken from 0-30, 30-60 and 60-90 cm soil depths, and
analyzed for ammonium and nitrate concentrations. Plant samples were also taken during harvest, and analyzed
for N content for determination of total N uptake. There was considerable amount of ammonium and nitrate in
the soil profile during preplanting and postharvest. Since the soils were mostly heavy texture, there is tendency
to have ammonium also in the soil solution. However, ammonium concentration was far below the nitrate
concentration throughout the profile. Plant nitrogen uptake in the irrigation district was very close to the amount
that was applied by the local farmers. The results indicated that soil mineral nitrogen level is an important
criteria for fertilization practices, especially the preplant Nmin values need to be considered to decrease the
amount of N fertilizer that will be applied
