ON THE IMPORTANCE OF SOIL HOMOGENEITY WHEN EVALUATING FIELD TRIALS

The existence of strong heterogeneity of soils on a scale of plots for field trials is demonstrated by a trial for fodder crops on a Lithic Rendoll in Upper Bavaria, Germany. Initial basic (pH, C-org, C-carb, texture) as well as physical (saturated hydraulic conductivity, bulk density, pore size distribution) soil properties vary strongly across a single plot. Due to the great extent of these variations, the effects of preceding and succeeding crops on soil structural properties within a subplot or subsubplot can only be evaluated with high uncertainty. The effect of weather on soil structural properties during the 18 month trial period must also be considered. Therefore, (i) no sampling of the soil at the end of the trial was done, and (ii) surveying the soil before designing field trials is recommended.