REQUIRED NUMBER OF CORN AND SOYBEAN PLANTS SAMPLED NECESSARY TO DETERMINE THE ELEMENTAL CONTENT OF THEIR LEAVES AT SPECIFIC ACCURACY AND CONFIDENCE LEVELS

A maximum crop yield depends upon a balanced supply of the 16 essentia l elements throughout the growth cycle. Achieving this balance can oft en be achieved by plant analysis guided fertilizer treatments. Samplin g is the first step when conducting a plant analysis. An extensive sur vey of the literature revealed a lack of published research that stati stically determined what number of plants must be sampled in order to obtain a representative sample. In our study, we utilized three field research sites in South Dakota, two locations planted to soybean (Glyc ine max L.) [Experiments 1 and 21 and the other to com (Zea mays L.) [ Experiment 3]. Ninety six plants were sampled at each site, collecting leaf tissue. After the leaf samples were collected, dried, and ground , they were analyzed for their N, P, K, Ca, Mg, S, Mn, and Zn content. Stein's equation, n = t2s2/d2, was used to estimate the number of pla nts required to be sampled in order to obtain a given level of precisi on and accuracy for each element. Our results indicate that the number of plants to be sampled in order to estimate the population mean for the elements assayed are 16 and 34 for soybean and com, respectively.