Saturday, 15 July 2006

Nutritional Disorders in Fruit Trees on the Calcareous Soils of Iran.

MJ Malakouti, Tarbiat Modares Univ, Soil and Water Research Institute, PO Box 14115-6185, Tehran, Iran

Experimental results show that orchard soils in Iran are primarily calcareous, with a pH above 7.5 and organic matter of less than 1%, and TNV exceeding 10%. However, there have been no salinity problems of concern in the orchards. One of the problems in orchard soils has developed as a result of over use of P-fertilizers with P accumulating in surface soils reducing the availability of the other nutrients below the critical demands in citrus orchards and vineyards where the fruit trees have performed poorly due to the resulting poor uptakes of Ca, Zn, B and Fe. Another problem of importance is poor management and concern for the quality of the irrigation water. Bicarbonate level of irrigation waters especially well waters show a high level of bicarbonate. The following suggestions are based on several years of investigations in orchards grown on the calcareous soils of Iran.

Fertilizer application on fruit trees must be in the form of fertilizer ditch or manure pit methods and should contain organic matter and elemental sulfur. No surface application of fertilizers should be tried. Neither should the materials be applied on the side of the bushes. P-fertilizers should not be applied as a phosphorus source under the present conditions due to the accumulation of phosphorus. There is no need for phosphorus applications where soil phosphorus level is about 5 to 7 mg P/kg and where the leaf phosphorus level is around 0.12%. 

Due to the fact that the fruit trees show deficient levels of Zn, B, Fe and Mn, balanced fertilization in addition to up to ten foliar applications of 0.4 to 0.5% solution of calcium chloride is recommended for apple orchards so as to attain N/Ca and K/Ca ratios of the apple fruits about 10 and 20, respectively. It is also recommended that flood irrigation be substituted with the pressurized systems, furrow irrigation and up to 75% of the local average water consumption where fruit trees are grown be applied. In order to improve the yield and fortify the fruits, the tree rhizospheres should be acidified using sulfur + thiobacillus (bio-fertilizer) containing fertilizers.

Keywords: Nutritional disorders; Calcium carbonate; Bicarbonate; Orchards; Micronutrient deficiencies; Yield and Quality.

The author wishes to acknowledge and thank the officials of the Agricultural Commission of the High Council for National Scientific Research, who made this research possible

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