Long-term comparative study of soil nitrate test, Gilat plant indicator method and wheat nitrogen uptake

A long-term comparison between two routine soil nitrogen tests, soil nitrate versus plant indicator method, was performed on the Negev Desert loessial soil in Israel. The Gilat plant indicator method was found to be a better method to reflect the soil nitrogen availability for wheat under field conditions. It was found that 15 to 38 kg ha-1 of NO3-N, measured by nitrate soil test, for each 30 cm soil increment, is not available for plant uptake. This plant unavailable NO3-N background in the soil cannot be leached by repeated irrigation cycles of 100 mm each, or by heavy rains.