USE OF SPATIAL PATTERNS OF SOIL PROPERTIES AND WHEAT YIELD IN GEOSTATISTICS FOR DETERMINATION OF FERTILIZER RATES

Researchers traditionally conduct fertilizer experiments on small, rep licated areas at university or governmental research centers. This app roach has two problems: (1) extrapolation of the results to large crop ped fields requires taking into account the impacts of spatial variabi lity of soil properties on the optimum amount and type of fertilizer t o apply and (2) farmers have limited access to the research work, part icularly in developing countries, which limits the information transfe r needed for farmers to adopt the recommended fertilizer techniques. W ith these problems in mind, field and laboratory investigations were c onducted on a farmer's field to study the spatial patterns of some soi l properties and wheat yield using geostatistics for determination of fertilizer rates. The field was divided into four parallel transects, and soil samples were collected at 15-m intervals along each transect. These soil samples were analyzed for different physical and chemical properties. A uniformity trial was conducted on wheat in the field. Cl assical statistical and geostatistical techniques were used to describ e the variability in measured soil properties and wheat yield. Most of the soil properties and wheat yield had a very high coefficient of va riation. Variability in soil properties and wheat yield was best descr ibed by a linear model. The potential wheat yield was estimated using the relationship between wheat yield and lime content, and was used in determining nitrogen (N) fertilizer rates for different areas. The ef fects of soil variability on crop growth and profitability of fertiliz er used were also demonstrated to the farmers.