Soil Exchangeable Nitrogen Retention at Various Soil Depths in Irrigated Cotton Production

Nitrogen management in row crop production systems is better understood with more data on various forms and amounts of soil exchangeable nitrogen throughout the soil profile. A field research was conducted in cotton (Gossypium hirsutum L.) under two furrow tillage treatments (conventional and conservation plow) and two fertilizer treatments (broadcast urea and side dressed UAN) each applied at a rate of 101 kg N ha^-1 arranged in a random complete block design with three replicates. Soil samples were then collected at four depth ranges (0-15 cm, 15-30 cm, 30-60 cm, 60-90 cm) and analyzed for concentrations of NH₄-N, NO₃-N, and NO2-N.. The type and form of N fertilizer applied influenced the concentrations and type of N found in surface layer of soil. Beyond 30 cm soil depth concentrations of all N forms were small.