Dividing fields into a few relatively homogeneous management zones (MZs) is a practical and costeffective approach to precision agriculture.There are three basic approaches to MZ delineation using soil and/orlandscape properties,yield information,and both sources of information.The objective of this study is to propose an integrated approach to delineating site-specific MZ using relative elevation,organic matter,slope,electrical conductivity,yield spatial trend map,and yield temporal stability map (ROSE-YSTTS) and evaluate it against two other approaches using only soil and landscape information (ROSE) or clustering multiple year yield maps (CMYYM).The study was carried out on two no-till corn-soybean rotation fields in eastern Illinois,USA.Two years of nitrogen (N) rate experiments were conducted in Field B to evaluate the delineated MZs for site-specific N management.It was found that in general the ROSE approach was least effective in accounting for crop yield variability (8.0％-9.8％),while the CMYYM approach was least effective in accounting for soil and landscape (8.9％-3 8.1％),and soil nutrient and pH variability (9.4％-14.5％).The integrated ROSE-YSTTS approach was reasonably effective in accounting for the three sources of variability (38.6％-48.9％,16.1％-17.3％ and 13.2％-18.7％ for soil and landscape,nutrient and pH,and yield variability,respectively),being either the best or second best approach.It was also found that the ROSE-YSTTS approach was effective in defining zones with high,medium and low economically optimum N rates.It is concluded that the integrated ROSE-YSTTS approach combining soil,landscape and yield spatial-temporal variability information can overcome the weaknesses of approaches using only soil,landscape or yield information,and is more robust for MZ delineation.It also has the potential for site-specific N management for improved economic returns.More studies are needed to further evaluate their appropriateness for precision N and crop management.
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