The impact of topography on soil properties and yield and the effects of weather conditions

Quantitative knowledge of the factors and interactions affecting yield is essential for site-specific crop management. One of the factors that frequently affects yield is topography. The aims of this study were to compare elevation data obtained from a combine harvester yield monitor and a hand RTK-GPS, and to evaluate the relationships between the spatial variation of cereal yield, selected crop nutrient concentration and topographic attributes derived from the two sources of elevation data. Simple models of elevation, slope and flow accumulation were created from the data of an experimental field in the Czech Republic, and the relations between yield and soil nitrogen and organic carbon contents and topography were determined over a four-year period. The models of elevation, slope and flow accumulation were compared with the yield, and soil nitrogen and organic carbon contents during the growing seasons of 2004, 2005, 2006 and 2007 in relation to total precipitation and temperature. The relationship between yield and topographic attributes was evaluated with the help of geostatistical methods. The results of correlation analysis among the variables were evaluated statistically by forward stepwise linear regression. No significant differences between elevation data from the combine harvester yield monitor and RTK-GPS were found. There was a significant relation between yield and crop nutrient concentration with topography. The correlation coefficients between flow accumulation and yield were weak for the wetter years and strong for the drier years.