The objectives of this paper were to study the influence of nitrogen fertilization on crop production using a linear mixed effects model with a first order continuous autoregressive correlation structure. On a 2-ha field, the most relevant soil properties were determined. Four fertilizer treatments were applied in a completely randomised block design with four replications (blocks) and repeated crop measurements were made in three crop seasons. The most relevant sources of variation in wheat production might not be ascribed to management of soil fertilization but to soil intrinsic variation and between-season variability. More advanced methods of statistical analysis need to be used to separate the residual error from error sources
