Abstract

The stationary field experiment of increasing rates of phosphorus (P) fertilization started in spring 2011 on calcareous alluvial soil of Posavian Canton in Federation of Bosnia and Herzegovina (B&H). The level of plant available P was found to be low by previous soil tests carried on with ammonium-lactate-method (7.06 pH in 1 M KCl; 4.17% organic matter; 3.79% CaCO3; 5.4 mg P2O5 in 100 g of soil). Five rates of P fertilizers (monoammonium phosphate: 13% N + 53 % P2O5) were applied as follows (kg P2O5 ha-1 ): a = 75 (basic fertilization), b = 225, c = 375, d = 525 and e = 975). The experiment was conducted in four replicates (basic plot 60 m2 ). Only basic fertilization was applied in the following years. Crop rotation was as follows: soybean (2011) - winter wheat (2012 + 2013). Soybean yield increased for 20% (2.11 and 2.53 t ha-1 , respectively) with P fertilization from 75 to 375 kg P2O5 ha-1 , whereas further increase of P rates resulted with lower yield compared to the control level. In both years significant differences of wheat yields were found only between basic and each rate of the increased P fertilization. Wheat yields of the control group were 6.21 and 6.44 t ha-1 , for the harvest of 2012 and 2013, respectively. P fertilization led to an increase in wheat yields up to 13% in 2012 and 15% in 2013. Mean values of wheat yields of four P treatments (b+c+d+e) were 6.92 and 7.21 t ha-1 for 2012 and 2013, respectively.