Relationship of soil potassium forms with maize potassium contents in soils derived from different parent materials

Abstract

Understanding of soil potassium (K) dynamics is essential for sustainable crop production. Bioavailability of potassium depends on forms and distribution within the soil profile. The objectives of this research were to determine which soil potassium forms controls the maize (<em>Zea mays</em>) potassium contents and compare the extracting capability of sodium tetraphenylborate (NaTPB) with ammonium acetate (NH₄OAc) method. Nine soils representing three different parent materials <em>i.e.</em> loess, sandstone and shale were sampled at three surface genetic horizons. Within each parent material, three soils at varying level of development were selected. Besides basic soil parameters, K was fractioned into water soluble K, exchangeable K, non-exchangeable K, and NaTPB-extracted K. The maize was sown in pots having 2 kg soil from each genetic horizon. Crop was harvested at seven weeks and plant was analyzed for K contents. Results shows that NaTPB extracted K gave best correlation as compared to NH₄OAc method. This conveys that a non-exchangeable K portion that becomes available to plants can better estimated by NaTPB method than NH₄OAc extraction.