Agronomic consequences of potential management zones delineated on the basis of EM38DD measurements

摘要

This study was conducted to investigate the feasibility of dual dipole apparent electrical conductivity (ECa) measurements obtained with an EM38DD sensor as an explicit information source to delineate potential management classes in an agricultural field in the Polder area of Belgium. The success of class delineation was evaluated In relation to soil physical-chemical properties and sugar beet yield. The average apparent electrical conductivity (ECa-A) derived from vertical and horizontal dipole measurements was capable of delineating 3 relatively large management classes. The analysis of variance of soil properties indicated that topsoil sand and lime and subsoil clay, sand and lime were largely different across these classes (all having a proportion of the variance accounted for by a classification of > 0.5). During the growing season of 2005, we monitored topsoil NO3--N and moisture content and found strong differences among classes. As a result, the crop biomass at harvest (roots plus leaves) was strongly variable between classes (ranging from 105 Mg ha(-1) to 153 ha(-1)), as well as the sugar content (ranging from 15.4% to 17.2%). However, due to a compensation effect between the crop biomass and sugar accumulation, differences in sugar yield and financial income between classes were relatively small (the income ranged from 3950 E ha(-1) to 4230 E ha(-1)). However, these-income values resulted from strongly different growing conditions, calling for a class-specific management. The image of the average ECa was found to be a reliable basis for delineating agronomically relevant management zones.