Potassium fertilization: paradox or K management dilemma?

• Published in: Renewable agriculture and food systems 2015-04, Vol.30 (2), p.115-119
• Main Authors: Bar-Yosef, B., Magen, H., Johnston, A.E., Kirkby, E.A.
• Format: Article
• Language: English
• Subjects: Agricultural production; Commentary; Crop yield; Crops; Exchange; Fertilization; Fertilizer application; Fertilizers; Illite; Montmorillonite; Paradoxes; Potassium; Soil (material); Soil chemistry; Soil testing; Studies; Uptakes
• ISSN: 1742-1705; 1742-1713
• DOI: 10.1017/S1742170514000295

In 2014, Khan et al. presented evidence that soil exchangeable K (Exch-K) increases over time without addition of potassium (K) to the soil despite the removal of K in crops on a soil rich in montmorillonite and illite. The authors term this behavior ‘The potassium paradox’. From their review of the literature, the authors also report a lack of crop response to potassium chloride (KCl) fertilization. Close evaluation of these findings reveals that their observations can be interpreted and predicted using current knowledge of K in soil chemistry and its uptake by plants, and there is no paradox in K behavior in the soil–plant system. There is also no evidence of a detrimental effect of KCl on crop yield or quality. Their conclusion that the widely used Exch-K soil test is inadequate for managing K fertilization is discussed and some possible modifications to improve its performance are included. We believe that measurement of Exch-K is an essential and valuable tool and its use should be continued, along with improvements in recommending K fertilizer application.