Mineral nutrient status of corn in relation to nitrate and tong-term waterlogging

The effect of nitrate nutrition and long-term waterlogging on the pattern of accumulation of inorganic nutrients in different plant organs was studied in corn (Zea mays L.) in glasshouse conditions. Continuous flooding of soils with NO, added for 21 days, caused a complete depletion of NO3, but in turn NH4-N increased significantly in these soils. Potassium (K) and phosphorus (P) contents in the flooded soils also increased whereas calcium (Ca) and magnesium (Mg) contents remained unaffected. Iron (Fe) and manganese (Mn) contents increased manifold as a result of flooding. Long-term flooding caused a marked reduction in dry weight of both shoots and roots, and supplementary NO3-N exacerbated the inhibitory effect of waterlogging on plant growth. A considerable decrease in nitrogen (N), P, and K contents in leaves was observed as a result of flooding, whereas in roots the reverse was true. However, N and P contents under waterlogged conditions increased consistently with an increase in the applied NO3 level. Flooding caused a marked reduction in Ca in both leaves and roots, and Mg only in leaves. Enhanced soil NO3-N had no effect on the concentration of Ca and Mg in leaves or roots. Concentrations of Fe and Mn in leaves and roots increased significantly due to continuous flooding, but a marked increase in these two nutrients was observed in roots. Addition of NO3-N to the waterlogged soils caused a slight increase in Fe in both leaves and roots but did not affect the Mn content in leaves or roots. Supplementary NO3-N was inhibitory to corn growth under long-term hypoxic conditions, particularly, the two higher concentrations (294 and 392 mg NO3-N kg(-1) soil).