Optimization of irrigation and nitrogen fertilization increases ash salt accumulation and ions absorption of drip-fertigated sugar beet in saline-alkali soils

•Irrigation and nitrogen effects on dry matter, ash salt accumulation, irons uptake of sugar beet were explored.•Dry matter and ash salt accumulation, Na+, K+, Ca2+ and Mg2+ uptake of W3 were smaller than those of W1 and W2.•Ash salt accumulation, Na+, K+, Ca2+ and Mg2+ uptake were proportional to dry matter accumulation.•Binary quadratic equations were fitted between water-nitrogen inputs and dry matter, ash salt accumulation and irons uptake.