KINETICS OF AMMONIUM AND POTASSIUM RELEASE UNDER ADDITION OF DIFFERENT LEVELS AND DOSES OF NITROGENOUS AND POTASH FERTILIZERS IN SOIL PLANTED WITH WHEAT (Triticum aestivum L.)

Abstract

ABSTRACT : Kinetics of ammonium and potassium release were studied in silty clay loam soil in order to describe ammonium and potassium releases from soil and how they are effected by addition of nitrogenous and potash fertilizers during the flowering and maturity stages of Wheat growth. Field experiment was carried out at a field belongs to crop science department , College of Agriculture ,University of Baghdad, by using three levels of nitrogen as urea (46%N) that were 0, 100 and 200 KgN.ha-1 , and three levels of potassium were added as K2SO4 (42% K) that were 0, 80 and 160 Kg K.ha-1 , their addition were at two doses (half before planting and half at flowering) and three doses (third amount before planting , third at tillering and the last third at flowering ).Wheat seeds of class( IPA99 ) were planted during the winter season of 2010, using 140 Kg grains.ha-1.The result showed that kinetics of ammonium and potassium release from the soil were best described by diffusion equation and it explained presence of two stages of their releases, the first one described the release of the easily available forms and the second one described the release of the unavailable forms of ammonium and potassium at the flowering and maturity stages of Wheat. The values of the accumulated amounts of the released ammonium and potassium increased in all the nitrogenous and potash fertilizers treatments with time either added alone or together as three doses at flowering and maturity stages of Wheat. There were increases of potassium release constant values and decreases in ammonium release constants values in most of the nitrogenous and potash fertilizers treatments at flowering and maturity stages of wheat compared with their values in control treatments (N0K0) at the same last stages. The values of ammonium and potassium release constant (Kd) were lower in the maturity stages than the flowering stages in most treatments.