Effects of lime on effective cation exchange capacity and exchangeable cations on a range of New Zealand soils

The effect of lime on the effective cation exchange capacity (ECEC) and exchangeable cations of 18 New Zealand topsoils was measured. Liming increased ECEC on all soils and the change in ECEC per unit change in pH followed the order yellow-brown loams > northern and southern yellow-brown earths > central yellow-brown earths = yellow-grey earths = recent soils. These differences were correlated to organic carbon (r 2 = 0.32), iron extractable with Tamm's oxalate reagent (r 2 = 0.43) and exchangeable aluminium (r 2 = 0.18). Virtually all of the newly created exchange sites were taken up by calcium. Liming generally decreased exchangeable magnesium and there was also evidence that exchangeable postassium was decreased by liming on some soils. When present, M KCl-exchangeable aluminium and manganese were predictably decreased by liming. Thus, despite the fact that most of the soils studIed had large amounts of variable negative charge, manipulation of this charge by liming may not result in greater retention of cations other than calcium.