Monday, November 13, 2006

Spatial and Temporal Variability of Soil Sampling Across a Pasture Field.

Solomon Kariuki, Travis Hanks, and Hailin Zhang. Oklahoma State Univ., Dept. of Plant and Soil Sciences, 368 Agriculture Hall, Stillwater, OK 74078

Spatial and temporal variabilities in soil test for essential plant nutrients influence how well producers are able to fertilize their fields and comply with environmental regulations, especially when animal manure is applied. The objective of this study was to determine the effect of spatial and temporal variability on soil test in a pasture system. Soil samples were collected from a 6 ha pasture field using different sampling methods. Three independent whole field samples were collected by three samplers, and each sample was split into three independent subsamples before submitting to the lab. The field was then divided into 15 grids. A 20-core random composite sample, a single point from the center and sample consisting of 10 cores near the center of each grid were collected. The whole field sampling was repeated monthly for one year.  All samples were tested for soil pH, organic matter, and plant available N, P, and K. A complete random design (CRD) was used to compute the treatment mean differences among the sampling techniques and among the samplers. Differences (P < 0.1) were found among the different methods of sampling indicating the presence of spatial variability in a specific analyte. The technique of soil sampling is crucial in explaining spatial variability of measured soil properties.