Effects of levels of nitrogen fertilizer on oxalate and some mineral contents in napiergrass (Pennisetum purpureum Schumach)

Abstract

AbstractIn a number of plant species, nitrogen fertilization leads to a higher oxalate content of the plant. Various tropical grasses sometimes contain oxalate in sufficient concentrations to induce calcium deficiency in grazing animals. The present study was undertaken to investigate the effect of increasing level of N (0, 10, 30, 60 and 90 g N m−2 using urea) on oxalate and some mineral contents in napiergrass (cv. dwarf‐late). We found that the total dry matter yield increased significantly (P < 0.001) with increasing N up to 30 g N m−2 applied, but no significant difference was observed among the N levels of 30, 60 and 90 g m−2. The oxalate content was not increased with increased levels of N fertilization in all cut forages, except for insoluble oxalate content at third‐cut forage which increased significantly (P < 0.05) with increased level of N fertilizer. The content of soluble oxalate in plants was positively correlated (r2 = 0.76, P < 0.001) with potassium concentration, while the content of insoluble oxalate was positively correlated with calcium (r2 = 0.69, P < 0.001) and magnesium (r2 = 0.65, P < 0.001) concentrations. The study suggests that while applying N fertilizer as urea during cultivation of napiergrass, oxalate accumulation may not be a matter of concern.