Efficiency of rock-feldspar combined with silicate dissolving bacteria on yield and fruit quality of valencia orange fruits in reclaimed soils

Abstract

This investigation was carried out through three successive seasons (2008 & 2009 and 2010) on 20 years old Valencia orange trees budded on sour orange rootstock, cultivated in a private orchard with loamy soil texture, at El Giza Governorate. The purpose of this study was to found an alternative source of potassium fertilizer locally termed "Feldspar", obtained as natural rocks which inoculated with dissolving bio-fertilizer. Their effect on leaf K content, physical properties, yield and juice quality of Valencia orange fruits were checked. Selected trees were fertilized with Fine powder of the rock K-Feldspar at rates (500, 750 and 1000g K2O/tree) in three dates i.e (October, March and July). Each application rate was applied either once at October or in two equal portions at October & March or in three portions at October, March and July. K-Feldspar substrate was inoculated with the bio-fertilizer Silicate dissolving bacteria. Leaf K content for different treatments were determined comparing with the traditional fertilizer potassium sulphate treatment at 600g k2O /tree in two equal portions during February and August. Obtained results revealed that, using feldspar inoculated with Bacillus circulans as soil application had a significant effect for improving leaf K content, fruit weight, yield and fruit quality as kg/tree, especially when added at 1000g k2O/tree in two or three portions. Also, feldspar treatment at 750g k2O/tree in two portions gave positive results where such treatments considered the promising under orchard conditions. Meanwhile, 500g k2O /tree at any dose recorded generally less response. Therefore, It could be recommended to fertilize Valencia orange orchards with feldspar at 1000g k2O/tree inoculated with the bio-fertilizer Bacillus Circulans in two (October& March) or three equal portions (Oct.& Mar. and July) instead of chemical fertilizers i.e, (potassium sulphate) to reduce environmental pollution and alleviate the dependence of imported or costly commercial fertilizers.