Response of Valencia Orange to Some Natural and Synthetic Soil Conditioners under North Sinai (Egypt) Conditions

During 2012 and 2013 seasons at El-Sheikh Zuwayid, North Sinai Governorate (Egypt) to examine the effect of humic acid and uni-sal applications as soil conditioners on leaf area, total chlorophylls, N, P, K, Fe, Zn and Mn in the leaves, yield as well as some physical and chemical characteristics of the Valencia orange fruits. Nine treatments were conducted as follows: control (untreated trees); humic acid (12, 18, 24 and 30 cm /tree) and uni-sal (12, 18, 24 and 30cm /tree). All treatments were applied at growth start, after full bloom, and at three weeks later after setting. The obtained results reveled that all treatments were very effective in stimulating growth parameters (total leaf area, chlorophyll, nitrogen, phosphorus, potassium, iron, zinc and manganese), yield and physical and chemical characteristics of the fruits. Generally, the best treatments were 30 cm uni-sal / tree in improving the leaf area, nutrients (N, P, K, Fe, Zn and Mn), fruit length, diameter, weight, volume, juice percentage, total sugar, reducing sugar and ascorbic acid in addition decreasing total acidity. In the same sequence, 30 cm uni-sal / tree and 24 cm uni-sal / tree enhanced total chlorophyll, yield, number of fruits/tree and (T.S.S.).