Ionic Balance in Coastal Bermudagrass Influenced by Nitrogen Fertilization and Soil Salinity1

Abstract

AbstractA stimulus in yields of coastal bermudagrass [Cynodon dactylon (L.)] with N on moderately saline soils previously reported may be due to cation‐anion balance. Other investigators have shown that a normal organic anion (C‐A) concentration was one of the conditions necessary for maximum growth, and they have postulated that yield response to N fertilization of saline soils was due to the substitution of NO3 for Cl and an increase in (C‐A) concentration of the grass. The objective of this study was to compare the relation between yield and (C‐A) concentration of coastal bermudagrass under several N fertilizer‐soil salinity regimes.The grass was grown in pots in a greenhouse on Brennan fine sandy loam (Aridic Haplustalfs). The soil was salinized by treatment with saline water to develop four salinity treatments (S0, S1, S2, and S3) with electrical conductivities (EC) of 1.2, 4.8, 9.6, and 14.4 mmho/cm, respectively. Fertilizer treatments were applied in a factorial arrangement with N rates of 0, 67, 133, and 200 mg/kg of soil and P rates of 0, 20, 40, and 60 mg/kg. The concentration of organic anions in the grass was determined as the difference between the concentration of cations (Na, K, Ca, Mg) and of inorganic anions (Cl, NO3, H2PO4, SO4).Nitrogen fertilization increased the (C‐A) concentration of the grass at all salinity levels. The increase in Cl concentration with increasing salinity decreased (C‐A) concentrations. An increase in growth was associated with an increase in the (C‐A) concentration. However, SO4 deficiency apparently controlled growth on the adequately N fertilized nonsaline soil, and cation accumulation in the salinized soils depressed growth.