Effect of nitrogen rate and source on growth and leaf mineral content of young navel orange trees

الملخص EN

This study was carried out through two successive seasons (2007 and 2008) in a private orange orchard in Qalubia governorate Egypt in a two years old Navel orange trees budded on sour orange rootstock on clay loam soil (Typic Torriorthents).

Planting distance was 2.5 * 5 meters apart and flood irrigation was used by river Nile water.

Insiabin (urea formaldehyde slow release nitrogen fertilizer 40 % N) and ammonium nitrate (33 % N) were applied as two sources of nitrogen each at three rates 100, 200 and 400g actual amount of nitrogen / tree / year.

Insiabin was divided into two equal doses, the first added in February and the second was added in May but ammonium nitrate was added into five monthly equal doses from February to June.

Ammonium nitrate at 100 or 200 g N / tree / year showed the highest stem thickness increment.

Ammonium nitrate at 100 g N / tree / year gave the highest leaf area value but insiabine at 100 g N / tree / year recorded the highest leaf dry matter percentage.

Most macro and micro nutrients (N, P, K, Ca, Mg, Fe, Zn and Mn) were not affected by the used nitrogen rate and source.

It could be recommended the use of ammonium nitrate at 100 g N / tree / year into five monthly equal doses from February to June at second and third year of Navel orange tree age.

Such application led to reduce the loss of fertilizer by leaching.

The obtained data showed that, insiabine treatment at 400 g N/tree/year remained the highest soil total nitrogen Key words.