Soil temperature and nitrogen effects on response of flooded and nonflooded rice to zinc

Summary Response of direct seeded rice (cv. Bluebelle) to Zn was studied in flooded and nonflooded (field capacity) Crowley soil (pH 7.6) maintained at soil temperatures of 18 and 30°C. Urea and (NH₄)₂SO₄ were compared as sources of N to determine their effect on plant uptake of Zn from ZnSO₄ either mixed or surface applied to the soil. Grain yields were slightly higher from nonflooded than from flooded soil. Higher dry matter production at 30 than at 18°C was not related to Zn nutrition. Urea and (NH₄)₂SO₄ resulted in similar yields and Zn uptake by flooded rice, but (NH₄)₂SO₄ was superior for nonflooded rice in the absence of applied Zn. More fixation of mixed Zn by the limed Crowley soil probably caused its lower effectiveness, as compared to surface-applied Zn.