ABSTRACT
Using appropriate soil sampling techniques can increase energy efciency and reduce the amount of nutrients required to maximize yields. Many crop nutrient needs and rates are determined through the use of soil testing.1 Soil nutrient recommendations protocols, which relate a soil nutrient extractant or other measurements with a relative supply and availability for specic crops, have been developed for most of the United States and many parts of the world. These procedures are constantly under scientic scrutiny for their continued usefulness and levels of condence (North American Prociency Testing Program, Soil Science Society of America, Madison, WI). This chapter presents methods of obtaining representative grid samples and processing them in a manner that will maximize condence in the resulting nutrient recommendations. There are many geographic areas in which zone sampling has replaced grid sampling; however, some of the principles presented here should also be considered in zone-sampled elds. Data and directions for calculating inverse distance weighting (IDW) factors and semivariances are provided.
