Contents lists available at ScienceDirect Agricultural Systems journal homepage: www.elsevier.com/locate/agsy Geospatial modeling of conservation tillage and nitrogen timing effects on yield and soil properties F.M. Liben a, *, C.S. Wortmann a , A. Tirfessa b,c a Dept. Agronomy and Horticulture, Univ. of Nebraska, Lincoln, NE 68583, United States b The Univ. of Queensland, Queensland Alliance for Agriculture and Food Innovation, St Lucia, QLD 4072, Australia c Ethiopian Institute of Agricultural Research, P.O.Box 436, Adama, Ethiopia ARTICLE INFO Keywords: Crop model Conservation Maize Nitrogen Rotation Tillage ABSTRACT Crop growth simulation can complement field research for adapting and targeting practices to diverse pro- duction areas. Two simulated experiments of 30-year duration were conducted with CERES and CROPGRO to evaluate the effects of fertilizer N practices and conservation tillage (CT) alternatives on maize (Zea mays L.) grain yield, soil organic C and soil organic N for seven technology extrapolation domains (TED) in Ethiopia. Mean maize grain yield was 663 kg ha -1 more with three compared two N applications per season for high rainfall TED in western Ethiopia. Tillage did not affect response to N. Averaged across TED, maize yield was 33% more with a combination of conservation tillage, rotation and additional N application (CT r+N ) compared maize monoculture with conventional tillage and the recommended N rate (CP mm ), primarily because of crop rotation. Maize grain yield increased over time with the conservation tillage under rotation (CT r ) but declined under CP mm . Soil organic C and N declined over time, but the rate of decline was lower with CT r+N compared to CP mm . Stored soil organic C and N were 8543 and 594 kg ha -1 more with CT r+N compared with CP mm, respectively, averaged over the 30 years. First order stochastic dominance analysis from maize grain partial net returns showed that maize rotation dominated maize monoculture. Second order stochastic dominance analysis for partial net return indicated the absence of an unambiguous dominant of conservation tillage for a farmers’ preference of low risk to higher net return or high net return to low risk. 1. Introduction Agriculture accounts for 46% of the gross domestic product and 85% of total employment in Ethiopia (Admassu et al., 2013a). Land degradation and declining soil fertility due to conventional crop pro- duction (CP), soil water deficits due to low and erratic rainfall, and inadequate use of good practices are constraints to sustainable crop intensification (Admassu, 2013b). Increased climate variability will challenge sustainable crop intensification which will require good spatial and temporal adaptation and targeting of practices. Conservation tillage (CT), by definition, requires crop rotation, little or no tillage, and retention of crop residue in the field. It has been recommended as a more sustainable crop management alternative to CP but has had very little adoption by smallholder farmers in Ethiopia (Liben et al., 2017, 2018a). Maize (Zea mays L.)-soybean (Glycine max L.) or maize-dry bean (Phaseolus vulgaris L.) rotation or intercropping systems, in addition to maize monoculture, are practiced in most major maize producing technology extrapolation domains (TED) of Ethiopia. Maize yield in Ethiopia could be doubled with application of good TED- specific practices possibly including optimized N use, crop rotation, reduced tillage, and crop residue retention. Information for CT and N use variables are available for only a few TED while maize production in Ethiopia occurs across complex terrain, soil and climatic diversity. Conducting field research to adapt practices for TED-specificity would have a high monetary and time cost, but complementing field research with geospatial crop growth simulation research may greatly reduce these costs. Agroecological zones have been used to identify crop yield varia- bility and limiting factors, spatially target recommendations, compare yield trends, and analyze impacts of climate change on agriculture https://doi.org/10.1016/j.agsy.2019.102720 Received 4 April 2019; Received in revised form 30 September 2019; Accepted 8 October 2019 Abbreviations: AP, at planting; CT, conservation tillage; CP, conventional practice; NT, no-tillage; CP mm and CT mm , maize monoculture with CP or CT; CP sm and CT sm , soybean or dry bean monoculture with CP or CT; CP r and CT r , maize-soybean or dry bean rotation with CP or CT; CT r+N , maize-soybean or dry bean rotation with CT but with additional fertilizer N; DAP, days after planting; SOC and SON, soil organic C and N; TED, technology extrapolation domain ⁎ Corresponding author. E-mail address: feyeraliben@gmail.com (F.M. Liben). Agricultural Systems 177 (2020) 102720 Available online 12 November 2019 0308-521X/ © 2019 Elsevier Ltd. All rights reserved. T