Abstract: The characteristics, possible analysis methods and programs for mixed model analysis of soil nutrient trials with spatial and temporal effects were studied by using data collected from a field experiment in which the effects of tillage on nitrogen mineralization of leguminous in soil was conducted. The difference between the analysis of variance and the mixed linear model in analysis of these trials was discussed. The results show that the correlations between the trial errors are depended on different soil layers and time periods. The correlations are increased with narrow spatial and temporal distances. Compared with the mixed linear model analysis, the analysis of variance could result in higher type I or II statistical error rates. The mixed linear model could deal with error correlation and heterogeneity and fit these trial data well, therefore, the analysis of these trials using the mixed linear model is more reliable.