Influence of crop rotations and tillage systems on phosphorus and potassium stratification and root distribution in the soil profile

The combination of cropping rotation and tillaging for several years have altered the distribution of nutrients such as phosphorus (P) and potassium (K) in the soil profile. These long-term changes have led researchers to investigate the distribution of nutrients and the distribution of roots in alternate cropping and tillage systems. The purpose of this study was to clarify if and how interactions between tillage systems and crop rotation, in long-term plots, affected P and K distribution and root development, in the soil profile. This continuous long-term tillage study consisted of 8 treatments arranged in a randomized split-plot design and replicated three times. It consisted of one rotation treatment, corn (Zea mays L.) And soybean [Glycine max (L.) Merr.] and of continuous corn as the main plot. Three primary tillage operations (fall moldboard plow, fall chisel, and no tillage) were tested as subplot. We found a greater concentration of P in the upper layers of the soil regardless of the tillage system. The P stratification was characterized in no-till system as a result of a surface applied fertilizer without incorporation. Potassium concentration in the soil surface decreased in depth in the chisel and in the no-till treatments, presumably as a consequence of the fertilization. Phosphorus stratification stimulated root growth in conservation systems when compared to the conventional one.