Effects of Liming on Soil Magnesium on Some Soils in New Zealand

The mean urease activities of the pasture and tillage counterparts of 10 soil series were 103 ± 44 and 75 ± 26 jjg urea-N hydrol. g - h respectively. Significantly (p<0.01) greater activity was recorded in the pasture variety of 8 series and in the tillage variety of 2 series. Multiple regression analysis showed that var-2 var-iations in the activities of the pasture soils (R = 95.9%) and of 2 the tillage soils (R = 97.3%) was attributable to variations in total-N, unbuffered and pH-dependent CEC, pH and silt, as well as C:n ratio in the case of the pasture group. The best-fit regression for the latter soils was obtained when individual cations re- placed CEC parameters (R = 99.8%). Individual soil properties each accounted for a small proportion of the total variation. The results suggest that agricultural soils should be grouped by land-use for best prediction of their urease activities. Differences between the activities of the pasture and tillage soils were highly correlated with the differences between their organic-C and exchangeable Mg contents.