The Role of Different Nitrogen Sources Combined with Foliar Applications of Molybdenum, Selenium or Sucrose in Improving Growth and Quality of Edible Parts of Spinach (Spinacia oleracea L.)

Two pots experiments, at two successive winter seasons, were carried out to investigate the effects of two nitrogen (N) sources (ammonium nitrate and urea) and foliar applications of molybdenum (Mo), sucrose (Suc) or selenium (Se) on the growth and quality of the edible parts of spinach (Spinacia oleracea L. cv. Balady). The results indicated that the growth and quality of spinach plants can be greatly determined by the applied N source. The edible parts of spinach plants that received urea as N source showed lower content of NO_3-, soluble oxalate, insoluble oxalate and total oxalate plus higher level of P content, however, higher moisture content as well as lower accumulation of dry mass, vitamin C and Fe were also observed in both seasons. Among the tested foliar applications at different concentrations, the treatment with 10% sucrose showed superior effects for increasing spinach growth (increase fresh weight, dry weight and leaves area) and quality (increase the contents of N, P, K, Ca, Fe, total protein and chlorophyll, as well as decreasing the contents of soluble oxalate and total oxalate) relative to the control (distilled water) in both seasons. The interaction treatment of urea fertilizer with foliar application of 10% sucrose was the most efficient one in decreasing NO_3- and soluble oxalate contents without reductions in growth (fresh and dry weights), the contents of vitamin C and minerals against the corresponding control in both seasons.