Effect of source and rate of nitrogen fertilization on yield, fruit quality and leaf mineral composition of valencia orange trees grown in Riyadh, Saudi Arabia

Abstract

This investigation. was carried out during 1992 and 1993 seasons to study the influence of ammonium sulfate and urea at different rates (0, 250, 500, 750, and 1000 g N/tree) on the yield, fruit quality and leaf mineral composition of Valencia orange trees growing in Riyadh. The results revealed that there were no significant differences in the yield, physical and chemical properties of the fruits due to sources of nitrogen applied. Whereas, rates of nitrogen markedly affected the yield and most of fruit properties in both seasons. In addition, yield and fruit properties were responded positively to increasing the rates of nitrogen up to 750 and 1000 g N/tree as compared with the control and the lowest rate of nitrogen. However, the nitrogen fertilization was more effective and pronounced in the second season than in the first one. Concerning leaf analysis, data showed that the application of ammonium sulfate as a nitrogen source produced a significant increase in the leaf nitrogen content as compared with applying urea. Furthermore, increasing nitrogen rates resulted in a significant increase in leaf nitrogen content than that of the control. No obvious effect was found in leaf macro or micronutrient contents between both sources of nitrogen applications. On the other hand, increasing rates of nitrogen caused marked increase in leaf Mg and Cu contents, slight increase in leaf Fe and Mn contents, and marked decrease in leaf K and Na contents as compared with the control. However, leaf P, Ca, and Zn contents were unaffected by the different rates of nitrogen application.