Soil tests measure the relative nutrient status of soil. The accuracy of a soil test is influenced by the laboratory analysis but may be influenced even more by the quality of the soil sample. Sample collection is extremely important in the accuracy and repeatability of a soil test. Sample handling following collection is also important. A soil sample which does not represent the area being sampled will be misleading and result in over or under-application of fertilizer. It is therefore very important to collect and handle soil samples properly.
Soil Sampling as a basis for fertilizer Application. Data regarding how, when and where to sample.
Soil Sampling for High Yield Agriculture. The text provides details especially regarding sampling patterns options but also sampling procedures, auxiliary data layers, sampling under different tillage systems.