Spatial Variability of Phosphorus and Potassium Contents - Effect of Long-Term in Soil Tillage Systems

Soil fertility and conservation tillage systems play important roles in agro–ecosystem productivity and preservation. Soil spatial variability of phosphorus (P) and potassium (K) was studied in different tillage systems. The objectives of this research included: (i) to assess the variability of P and K in three tillage systems: minimum tillage (MT), conventional tillage (CT) and no–till (NT), and depth of 0–0.1 m and 0.1–0.2 m, and (ii) to map their spatial distribution. The field experiment was conducted in a Rhodic Haplustox. The samples were collected in a regular grid of 10 × 5 m with regularly spaced lines of 10 m, resulting in 50 samples on each soil tillage system, in the depth of 0–0.1 m and 0.1–0.2 m. The spatial variability of P and K was determined by using the kriging maps. In the NT (depth of 0–0.1 m), the distribution and concentration P and K was more uniform in the area, and in the CT, due to inadequate management of the soil and topography of the terrain influenced the displacement of P via leaching and erosion. In the MT there were large patches of P and K pulverized by the area and a tendency of nutrient loss that occurs due to the erosive process of the soil, decreasing the nutrient of the soil. In the CT and MT, the altitude influenced the concentration of P and K in the 0–0.1 and 0.1–0.2 m layer, that is, the higher the altitude, the lower the concentration of P and K. Spatial variability of P and K in soil depends on both factors, degrees of mobility of nutrient, altitude and on management practices. Altitude (e.g. topography) and tillage systems variability in soil P and K concentration are potentially of agronomic importance.