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Site attributes used in for investigating the cropping network.

 
Attribute Case study 1 Case study 2 Case study 3
Site† Hamilton runoff site Cressy runoff site Hamilton research station
Soil type (Isbell, 2002) brown chromosol grey sodosol black vertosol
Soil type (Soil Survey Staff, 2006) mollic haploxeralf vertic natrixeralf xeric endoaquerts.
Subsurface soil texture clay sodic clay sodic clay
Surface cracking–facilitated drainage moderate weak strong
Surface slope high low low
Sealing topsoil yes yes yes
Surface soil texture fine sandy clay loam fine sandy loam clay
For additional detail of soil types, refer to http://www.dpi.vic.gov.au/dpi/vro/glenregn.nsf/pages/glenelg_soil_surveys_hri



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Sensitivity analyses of Dissolved Nitrogen Export Factor using the Bayesian Network for high rainfall cropping in south eastern Australia (assuming that the crop was canola, it was a medium rainfall year, and the field had been under continuous cropping and would be conventionally tilled).

 
Variance node Hamilton site Cressy site Hamilton research farm
Variance reduction Belief variance Variance reduction Belief variance Variance reduction Belief variance
Dissolved N export factor 13.8 0.519 14.0 0.519 13.97 0.519
Surface water 5.9 0.161 6.0 0.163 6.0 0.164
Total runoff 5.9 0.195 5.9 0.195 5.9 0.195
Subsurface water 4.8 0.142 4.8 0.142 4.9 0.142
Crop yield 4.0 0.125 4.0 0.125 4.0 0.125
Sowing fertilizer source factor 2.1 <0.001 2.2 <0.001 2.2 <0.001
Sowing fertilizer nitrogen 0.7 <0.001 0.7 <0.001 0.7 <0.001
Days between sowing and runoff 0.7 <0.001 0.7 <0.001 0.7 <0.001
Soil source factor 0.2 0.002 0.2 0.002 0.2 0.001
Fertilizer rate at sowing 0.2 <0.001 0.2 <0.001 0.2 <0.001
Estimated mineral nitrogen 0.1 0.001 0.1 0.001 0.1 0.001



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Results of interrogating the cropping Bayesian Network.

 
Node settings Node values
Transport conditions Crop Rainfall Yield Pasture/ley rotation Tillage practices Estimated mineral N Fertilizer rate at sowing Fertilizer type at sowing Surface water Subsurface water Soil source factor Plant source factor Sowing fertilizer source factor Dissolved N load factor
Surface-dominant flow midseason wheat medium default default default default default default 33.3 4.5 5.4 0.2 2.2 1.0
Subsurface-dominant flow midseason wheat medium default default default default default default 6.6 29.1 5.5 0.2 2.2 1.0
Surface-dominant flow canola medium default default default default default default 74.4 9.3 5.4 0.4 2.2 2.3
Subsurface-dominant flow canola medium default default default default default default 12.8 71.4 5.5 0.4 2.2 2.2
Surface dominant-flow barley medium default default default default default default 351.0 34.2 5.4 0.2 2.4 6.5
Subsurface-dominant flow barley medium default default default default default default 51.9 319.0 5.5 0.2 2.4 6.0
Surface-dominant flow canola medium high default default default default default 0.0 0.0 5.4 0.4 2.2 0.0
Surface-dominant flow canola medium medium default default default default default 51.9 9.5 5.4 0.4 2.2 3.3
Surface-dominant flow canola medium low default default default default default 484.0 45.2 5.4 0.4 2.2 6.7
Subsurf-ce dominant flow canola medium high default default default default default 0.0 0.0 5.4 0.4 2.2 0.0
Subsurface-dominant flow canola medium medium default default default default default 15.3 49.9 5.4 0.4 2.2 3.2
Subsurface-dominant flow canola medium low default default default default default 51.9 470.0 5.4 0.4 2.2 6.3
Surface-dominant flow canola medium medium default default high default default 51.9 9.5 6.8 0.4 2.2 3.7
Surface-dominant flow canola medium medium default default low default default 51.9 9.5 1.5 0.4 2.2 2.0
Subsurface-dominant flow canola medium medium default default high default default 15.3 48.8 6.9 0.4 2.2 3.8
Subsurface-dominant flow canola medium medium default default low default default 15.3 48.8 1.5 0.4 2.2 1.7
Surface-dominant flow canola medium medium continuous cropping no tillage default default default 51.9 9.5 4.9 0.4 3.1 3.4
Surface-dominant flow canola medium medium continuous cropping conventional cultivation default default default 51.9 9.5 5.9 0.4 3.1 3.1
Default default default default default default default high MAP† 163 29.4 5.4 0.27 4.4 4.5
Default default default default default default default nil MAP 163 29.4 5.4 0.27 0 2.6
Default default default default default default default high urea 163 29.4 5.4 0.27 3.6 4.1
Default default default default default default default nil urea 163 29.4 5.4 0.27 0 2.6
MAP, mono-ammonium phosphate.