Experiments in rectangular areas: Design and randomization

Agricultural experiments are often laid out in a rectangle in 3-5 replicates. Is it better to use a standard randomized complete-block design in rows, or a complete-block design in rows but with restricted randomization, or an efficient row-column design? These approaches differ in the variance of the estimator of a difference between two treatments, and in the bias of the estimator of that variance, as well as in the mechanics of constructing the design and analyzing the data. I conclude that when intra-column correlations are high then the row-column design is best but that when they are moderate the best procedure is to use an improved version of restricted randomization, which gives an unbiased estimator of the average variance in the single experiment performed.