Effect of potassium chloride topdressing on irrigated wheat in medium texture soils

The method potassium (K) fertilizer is applied in agricultural soils with a high K fixation capacity has a considerable effect on its use efficiency. To determine the effects of K fertilizer topdressing on irrigated wheat (Triticum aestium L.), experiments were performed during the years 2010, 2011, and 2013 under both field and experimental conditions in West Azerbaijan Province characterized by loamy soils as the dominant soil series with available K (Kava.) levels below 250 mg kg-1 (critical level). The experiments were arranged in a randomized complete block design with three treatments and four replications. Wheat was grown in early spring with varying topdressing K fertilizer levels (control, 100, and 200 kg ha−1 KCl) applied at the stem elongation stage. The results indicated that K fertilizer had no significant effects on either grain yield or its components. K concentration and uptake by the grain and straw were not affected by the treatments in which apparent K recoveries were measured below 7%. In contrast, soil Kava was significantly affected by K topdressing application. Lab tests revealed that more than 90% of the applied K fertilizer accumulated in the first six cm of the topsoil without being transferred to subsoil layers. A K fixation capacity of 45.5–54.5% with an average value of 51% was recorded for the soils in the region. Finally, it was concluded that both K sorption and fixation phenomena prevented K transfer from the surface layer to the plant root zone in the soils studied; hence, K topdressing in similar loamy soils would not be effective in meeting wheat K requirements.