Effect of Nitrogen, Sodium, and Potassium on Nitrate and Oxalate Concentration in Kikuyugrass

Abstract

Kikuyugrass was analyzed for nitrate (expressed as KNO 3 ) and soluble oxalate concentration after it was grown for 8 wk in nutrient solution supplemented with KCl, NaCl, or NH 4 NO 3 ; fertilized in the greenhouse with urea and KNO 3 at 112 kg N ha -1 ; and fertilized in the field in Hawaii and Panama with urea at 56 and 112 kg N ha -1 . Both treated and untreated kikuyugrass grown in nutrient solution contained toxic levels of nitrates and soluble oxalates. Plants treated with urea in the greenhouse contained 0.4% nitrate (nontoxic) 72 h after treatment whereas those treated with KNO 3 contained 2.36% nitrate (highly toxic). Fertilization of kikuyugrass with urea in Panama and Hawaii did not significantly affect soluble oxalate concentration, but nitrate concentration increased to potentially lethal levels (over 1.5% as KNO 3 , dry wt) in plants from Hawaii.