Soil tillage resistance as a tool to map soil type differences

Precision agriculture is based on spatial knowledge of soil and crop condit ions in the management decisions. In this paper, a method to improve determ ination of soil physical properties is proposed. Current practice is to ana lyse soil samples, taken at several locations in a field, for physical prop erties. To obtain a sound coverage, many soil samples have to be analysed. When soil properties are correlated, it is possible to reduce the number of soil samples of one property and enhance its spatial resolution with the i nformation of another, more densely sampled, property. In this study, infor mation gathered automatically during the major soil tillage operation, plou ghing, is used to improve the spatial resolution of sampled topsoil clay co ntent. Plough draught was measured during two seasons on a 6 ha field. The specifi c plough draught varied between 30 and 50 kNm(-2). Clay content varied betw een 6 and 22% and topsoil moisture content range was 120-240g kg(-1) during the first year and 180-300g kg(-1) in the second year. The specific plough draught maps of both years showed a similar spatial pattern with a cross c orrelation coefficient at zero distance of 0.6. The use of specific plough draught as co-variable in the co-kriging techniq ue made it possible to decrease the number of topsoil clay content samples from 60 to 18 ha(-1) with only 20% increase in prediction error. On this fi eld, the spatial variation in top soil clay content was correlated with the spatial variation of the crop yield. (C) 2001 Silsoe Research Institute.