Fixed NH4-N in relation to EUF-extractable K

Summary Representative arable soils from Hesse were investigated for their contents of fixed NH₄ ⁺ and EUF-extractable potassium in the rooting zone. Alluvial soils were found to be rich in fixed ammonium and low in EUF-extractable potassium, while soils of basaltic origin were low in fixed ammonium and rich in EUF-extractable potassium. A negative correlation (r=0.79^*) was found between fixed NH₄ ⁺ and EUF-extractable soil K⁺. The content of fixed NH₄ ⁺ in the soil profile showed considerable and significant changes during the growing season, which finding is supposed to be due to NH₄ ⁺ uptake by the crop.