The study looked at how water conditions and types of land use affect soil fertility in the Loess Plateau. They analyzed soil samples from different areas and found that irrigated soil had higher levels of certain nutrients, while non-irrigated soil had more organic matter. The variability of soil fertility was different depending on the type of land use, with some areas showing stronger spatial patterns than others. Overall, the variability in soil fertility is influenced by natural factors like soil structure, rather than human activities.