Wheat response to combined application of nitrogen and phosphorus in a saline sandy loam soil

Fertilization with nitrogen (N) or phosphorus (P) can improve plant growth in saline soils. This study was undertaken to determine wheat (Triticum aestivum L; cv Krichauff) response to the combined application of N and P fertilizers in the sandy loam under saline conditions. Salinity was induced using sodium (Na(+)) and calcium (Ca(2+)) salts to achieve four levels of electrical conductivity in the extract of the saturated soil paste (EC(e)), 2.2, 6.7, 9.2 and 11.8 dS m(-1), while maintaining a low sodium adsorption ratio (SAR; <= 1). Nitrogen was applied as Ca(NO(3))(2)center dot 4H(2)O at 50 (N50), 100 (N100) and 200 (N200) mg N kg(-1) soil. Phosphorus was applied at 0 (PO), 30 (P30) and 60 (P60) mg kg(-1) soil in the form of KH(2)PO(4). Results showed that increasing soil salinity had no effect on shoot N or P concentrations, but increased shoot Na+ and chlorine ion (Cl(-)) concentrations and reduced dry weights of shoot and root in all treatments of N and P. At each salinity and P level, increasing application of N reduced dry weight of shoot. At each salinity and N level P fertilization increased dry weights of shoot and root and shoot P concentration. Addition of greater than N50 contributed to the soil salinity limiting plant growth, but increasing P addition up to 60 mg P kg(-1) soil reduced Cl(-) absorption and enhanced the plant salt tolerance and thus plant growth. The positive effect of the combined addition of N and P on wheat growth in the saline sandy loam is noticeable, but only to a certain level of soil salinity beyond which salinity effect is dominant.