Available K decreased by 21% on a rice–wheat cropping system in Zhangjiagang County (Darilek et al., 2009), where decreasing soil K is, reportedly, one of the top fertility concerns (Sheldrick et al., 2003; Gao et al., 2006) andTKdecreasedby 9%onagriculturallandinSuzhouover an 18 year period (Li et al., 2007).