Methods of soil sampling in areas under no-tillage in the Southwest Goias

Soil sampling is the first and fundamental step in an evaluation program of soil fertility, and the recommendation of lime and fertilizer is defined through the interpretation of the results of chemical analysis of the sample. With the objective of evaluating the results of the chemical analysis of the soil as a function of the sampling method, soil samples were collected from 12 different areas that have been under no-tillage system for 2, 5 and 10 years. The Ducth auger hole and the electric drill were used to collect the soil samples at 3 different positions and 2 depths, evaluating the soil fertility as a function of time of the direct planing system. There was an increment of P in areas with 10 years under no-tillage system in comparison with the others areas. The values of Ca, Mg, P, K, pH, CTC and V showed concentration gradient as a function of time of no tillage, superficial application of lime and fertilization in the planting rows. The sampling equipment influenced the results of soil analysis, and all macronutrients except S and all micronutrients, showed higher values when soil was sampled with the electric drill.