Soil Maps of Cadmium in New Zealand

3. Results and Discussion - 3.5 Future Levels of Cadmium in New Zealand

Future levels of cadmium in New Zealand were calculated using the New Zealand Fertiliser Manufacturers Research Association (FMRA) CadBal model. Based on measured data from the cadmium database, 287 scenarios were run and are summarised in Table 9. Full scenario data are found on pages 40 -44 of this report. Scenarios were run using average and range data for New Zealand as a whole and for regions.

The CalBal model indicated future soil cadmium concentrations would be higher under sheep/beef farming than under dairy farming after 100 years when both are under the same fertiliser regime (Figure 23) although, dairy farming requires more fertiliser for optimal production than beef and sheep farming. Dairy farming was shown to lead to more accumulation of cadmium in soil than sheep/beef farming when both are receiving more typical levels of fertiliser (50 kg ha-1 y-1 for dairy and 30 kg ha-1 y-1 for sheep/beef) (Figure 24). The sedimentation losses used by the model are oversimplified as sedimentation losses are due to a range of factors including topography, soil type, leaching class and climate, not just farm type. Table 10 shows the variation in total suspended sediment (TSS) measurements for different landuses, topography and soil type reported in 5 publications. It appears likely the sedimentation losses used by the model are overestimated for flat land and should be adjusted. In addition, the model gave no consideration to deposition of eroded sediment from steep land to flatter land, animal relocation of cadmium through faeces or land application of dairyshed effluent.

Table 10: Comparison of sediment yield for different landuses, topography and soil type

Site Name Farm Type Topography Soil type TSS (kg ha-1 y-1)
Whatawhata Research Centre1 Sheep & beef Mainly steep land Brown and Ultic Soils, patches of Allophonic Soils 600–3212
Toenepi1, 2 Dairy Rolling to flat Recent and Granular Soils 142
Purukohukohu1,3 Sheep & beef Moderately steep Pumice Soils 22
Moutere4 Pasture Moderately steep Brown Soils, some Recent, Podzols, Ultic, Melanic and Gley Soils 210, 320, 670, and 790
Moutere4 Forestry Moderately steep Brown Soils, some Recent, Podzols, Ultic, Melanic and Gley Soils 40
Big Bush4 Native Bush Moderately steep Brown Soils, some Recent, Podzols, Ultic, Melanic and Gley Soils 60–110
Pukekohe5 Cropping Rolling Granular Soils 490–56800
Whatawhata Research Centre6 Sheep & beef steep land (tread damaged soil) Brown Soils 1666
Whatawhata Research Centre6 Sheep & beef Easy contoured land (tread damaged soil) Allophonic Soils 714

1 Quinn & Stroud (2002)
2 Wilcock et al. (1999)
3 Cooper & Thomsen (1988)
4 Basher (2003)
5 Basher et al. (1997)
6 Nguyen et al. (1998)

Table 9: Scenarios based on measured data from the cadmium database

Blank space = level not reached

  Farm type Fertiliser Rate (kg P /ha/y) Fertiliser Cd (mg/kg P) Soil Group sample depth (m) initial Cd (mg/kg) Cd at +100 years (mg/kg) Years to reach 1 mg/kg Years to reach 3 mg/kg
National Dairy 30 230 Alluvial 0.075 0 0.4199 724  
National Dairy 30 230 Gley 0.075 0 0.4604 602  
National Dairy 30 230 YBE 0.075 0 0.4278    
National Dairy 30 230 YBL 0.075 0 0.5022 587  
National Dairy 30 230 YBP 0.075 0 0.5162 470  
National Dairy 30 230 YGE 0.075 0 0.418 730  
National Dairy 30 230 YGE 0.075 0.31 0.5129 675  
National Dairy 30 230 YBL 0.075 0.5 0.6698 488  
National Dairy 30 230 YBE 0.075 0.64 0.7205 782  
National Dairy 30 230 Gley 0.075 1 1.0591 0  
National Dairy 30 230 Alluvial 0.075 1.09 1.1301 0  
National Dairy 30 230 YBL 0.075 1.35 1.3394 0  
National Dairy 30 230 YBP 0.075 1.51 1.4995 0  
National Dairy 30 230 YBL 0.075 2.36 2.1833 0  
National Dairy 38 230 YBL 0.075 0.5 0.9839 104  
National Dairy 38 230 YBL 0.075 2.36 2.5188 0 604
National Dairy 50 230 YGE 0.075 0 0.8412 125 522
National Dairy 50 230 YBE 0.075 0 0.9215 112 474
National Dairy 50 230 YBL 0.075 0 1.1897 81 339
National Dairy 50 230 YBP 0.075 0 1.1997 80 332
National Dairy 50 230 Gley 0.075 0 0.9874 102 425
National Dairy 50 230 Peat 0.075 0 1.6206 55 225
National Dairy 50 230 Alluvial 0.075 0 0.8755 119 487
National Dairy 50 230 BGCL 0.075 0 1.0884 90 379
National Dairy 50 230 YGE 0.075 2.52 2.9495 0 113
National Dairy 50 230 YBE 0.075 2.52 2.9832 0 104
National Dairy 50 230 YBL 0.075 2.52 3.1559 0 74
National Dairy 50 230 YBP 0.075 2.52 3.1734 0 72
National Dairy 50 230 Gley 0.075 2.52 3.0403 0 92
National Dairy 50 230 Peat 0.075 2.52 3.4652 0 48
National Dairy 50 230 Alluvial 0.075 2.52 2.9855 0 104
National Dairy 50 230 BGCL 0.075 2.52 3.0933 0 83
National Dairy 30 230 Gley 0.1 0.01 0.4027 802  
National Dairy 30 230 Gley 0.1 1.33 1.3414 0  
National Dairy 30 230 YBE 0.1 0 0.3751    
National Dairy 30 230 YBE 0.1 0.89 0.918 484  
National Dairy 30 230 YBL 0.1 0.14 0.4657 771  
National Dairy 30 230 YBL 0.1 1.31 1.3069 0  
National Dairy 30 230 YBP 0.1 0 0.4516 627  
National Dairy 30 230 YBP 0.1 1.55 1.537 0  
National Dairy 38 230 YBL 0.1 0.14 0.6635 199  
National Dairy 38 230 YBL 0.1 1.31 1.5639 0  
National Dairy 30 230 YBE 0.2 0 0.2643    
National Dairy 30 230 YBE 0.2 1.03 1.0367 0  
National Dairy 30 230 YBL 0.2 0.18 0.3697    
National Dairy 30 230 YBL 0.2 1.43 1.4205 0  

Table 9: Scenarios based on measured data from the cadmium database (Contd)

  Farm type Fertiliser Rate (kg P /ha/y) Fertiliser Cd (mg/kg P) Soil Group sample depth (m) initial Cd (mg/kg) Cd at +100 years (mg/kg) Years to reach 1 mg/kg Years to reach 3 mg/kg
National Dairy 38 230 YBL 0.2 0.18 0.4746 389  
National Dairy 38 230 YBL 0.2 1.43 1.5534 0  
National Lettuce 80 175 BGLC 0.15 0.62 1.5892 39 255
National Potato 45 175 BGLC 0.15 0 0.5957 171 556
National Potato 45 175 BGLC 0.15 0.89 1.445 20 405
National Potato 45 175 BGLC 0.15 0.89 1.447 20 405
National sheep / beef 30 230 Alluvial 0.075 0 0.5474 228 981
National sheep / beef 30 230 Gley 0.075 0 0.6293 188 809
National sheep / beef 30 230 YBE 0.075 0 0.5798 214 957
National sheep / beef 30 230 YBL 0.075 0 0.7384 151 666
National sheep / beef 30 230 YBP 0.075 0 0.7532 147 632
National sheep / beef 30 230 YGE 0.075 0 0.5438 230 990
National sheep / beef 30 230 YGE 0.075 0.31 0.7084 185 945
National sheep / beef 30 230 YBE 0.075 0.64 1.0074 98 842
National sheep / beef 30 230 Gley 0.075 1 1.3902 0 621
National sheep / beef 30 230 Alluvial 0.075 1.09 1.408 0 726
National sheep / beef 30 230 YBL 0.075 1.35 1.7897 0 442
National sheep / beef 30 230 YBP 0.075 1.51 1.9557 0 382
National sheep / beef 30 230 YBE 0.1 0 0.475 285  
National sheep / beef 30 230 YBE 0.1 0 0.475 285  
National sheep / beef 30 230 YBE 0.1 0.5 0.7936 177  
National sheep / beef 30 230 YBE 0.1 0.73 1.002 100  
National sheep / beef 30 230 YBL 0.1 0 0.6006 202 888
National sheep / beef 30 230 YBL 0.1 0.04 0.6131 199 885
National sheep / beef 30 230 YBL 0.1 1.1 1.4521 0 659
National sheep / beef 30 230 YBL 0.1 1.25 1.5911 0 618
National sheep / beef 30 230 YGE 0.1 0 0.4441 307  

Table 9: Scenarios based on measured data from the cadmium database (Contd)

  Farm type Fertiliser Rate (kg P /ha/y) Fertiliser Cd (mg/kg P) Soil Group sample depth (m) initial Cd (mg/kg) Cd at +100 years (mg/kg) Years to reach 1 mg/kg Years to reach 3 mg/kg
National sheep / beef 30 230 YGE 0.1 0.33 0.6329 242  
National sheep / beef 30 230 Alluvial 0.15 0.07 0.3669 443  
National sheep / beef 30 230 Alluvial 0.15 0.27 0.4935 383  
National sheep / beef 30 230 YBE 0.15 0 0.3598 427  
National sheep / beef 30 230 YBE 0.15 0.67 0.8567 181  
National sheep / beef 30 230 YGE 0.15 0 0.334 460  
National sheep / beef 30 230 YGE 0.15 0.66 0.8364 197  
National sheep / beef 30 230 YBE 0.2 0 0.295 570  
National sheep / beef 30 230 YBE 0.2 0.85 0.9841 113  
National sheep / beef 50 230 BGCL 0.075 0 0.6805 169 745
National sheep / beef 50 230 Peat 0.075 0 1.048    
Auckland Dairy 50 230 YBE 0.075 0.03 0.931 110 472
Auckland Dairy 50 230 YBE 0.075 1.1 1.739 0 348
Auckland Dairy 50 230 BGCL 0.075 0.03 1.0977 89 378
Auckland Dairy 50 230 BGCL 0.075 1.1 1.8836 0 278
Bay of Plenty Dairy 50 230 YBE 0.075 0.05 0.9381 109 471
Bay of Plenty Dairy 50 230 YBE 0.075 1.6 2.1769 0 271
Bay of Plenty Dairy 50 230 Gley 0.075 0.05 1.0042 100 423
Bay of Plenty Dairy 50 230 Gley 0.075 1.6 2.2389 0 241
Bay of Plenty Dairy 50 230 YBL 0.075 0.05 1.2053 79 337
Bay of Plenty Dairy 50 230 YBL 0.075 1.6 2.3869 0 193
Bay of Plenty Dairy 50 230 YBP 0.075 0.05 1.2157 78 331
Bay of Plenty Dairy 50 230 YBP 0.075 1.6 2.4024 0 188
Bay of Plenty Dairy 50 230 Alluvial 0.075 0.05 0.8935 116 484
Bay of Plenty Dairy 50 230 Alluvial 0.075 1.6 2.164 0 273
Canterbury Dairy 50 230 YGE 0.075 0.01 0.8444 125 522
Canterbury Dairy 50 230 YGE 0.075 0.89 1.4935 18 414

Table 9: Scenarios based on measured data from the cadmium database (Contd)

  Farm type Fertiliser Rate (kg P /ha/y) Fertiliser Cd (mg/kg P) Soil Group sample depth (m) initial Cd (mg/kg) Cd at +100 years (mg/kg) Years to reach 1 mg/kg Years to reach 3 mg/kg
Canterbury Dairy 50 230 Alluvial 0.075 0.01 0.8935 116 484
Canterbury Dairy 50 230 Alluvial 0.075 0.089 1.5309 17 385
Gisborne Dairy 50 230 YBE 0.075 0.05 0.9381 109 471
Gisborne Dairy 50 230 YBE 0.075 0.27 1.0517 93 455
Gisborne Dairy 50 230 Alluvial 0.075 0.05 0.8935 116 484
Gisborne Dairy 50 230 Alluvial 0.075 0.27 1.014 98 466
Hawkes Bay Dairy 50 230 YGE 0.075 0.05 0.8587 123 519
Hawkes Bay Dairy 50 230 YGE 0.075 0.63 1.2647 57 454
Hawkes Bay Dairy 50 230 Alluvial 0.075 0.05 0.8965 116 484
Hawkes Bay Dairy 50 230 Alluvial 0.075 0.63 1.3023 54 422
Hawkes Bay Dairy 50 230 YBE 0.075 0.05 0.9381 109 471
Hawkes Bay Dairy 50 230 YBE 0.075 0.63 1.3316 51 413
Hawkes Bay Dairy 50 230 YBP 0.075 0.05 1.2157 78 331
Hawkes Bay Dairy 50 230 YBP 0.075 0.63 1.5938 37 289
Manawatu Dairy 50 230 YGE 0.075 0.04 0.855 123 520
Manawatu Dairy 50 230 YGE 0.075 0.9 1.5023 16 413
Manawatu Dairy 50 230 Alluvial 0.075 0.04 0.8896 117 485
Manawatu Dairy 50 230 Alluvial 0.075 0.9 1.5398 15 383
Manawatu Dairy 50 230 YBE 0.075 0.04 0.9345 110 472
Manawatu Dairy 50 230 YBE 0.075 0.9 1.5643 15 377
Nelson-Mar Dairy 50 230 YGE 0.075 0.03 0.8513 124 521
Nelson-Mar Dairy 50 230 YGE 0.075 1 1.5913 0 397
Nelson-Mar Dairy 50 230 Alluvial 0.075 0.03 0.8859 117 485
Nelson-Mar Dairy 50 230 Alluvial 0.075 1 1.6287 0 368
Nelson-Mar Dairy 50 230 YBE 0.075 0.03 0.931 110 472
Nelson-Mar Dairy 50 230 YBE 0.075 1 1.6515 0 362
Northland Dairy 50 230 YGE 0.075 0 0.8412 125 522
Northland Dairy 50 230 YGE 0.075 0.67 1.2995 51 448
Northland Dairy 50 230 YBE 0.075 0 0.9215 12 474
Northland Dairy 50 230 YBE 0.075 0.67 1.3656 46 408
Northland Dairy 50 230 Alluvial 0.075 0 0.8755 119 487
Northland Dairy 50 230 Alluvial 0.075 0.67 1.337 48 416
Northland Dairy 50 230 BGCL 0.075 0 1.0884 90 379
Northland Dairy 50 230 BGCL 0.075 0.67 1.5206 37 326
Otago Dairy 50 230 YGE 0.075 0.03 0.8513 124 521
Otago Dairy 50 230 YGE 0.075 0.91 1.5112 15 411
Otago Dairy 50 230 YBE 0.075 0.03 0.931 110 472
Otago Dairy 50 230 YBE 0.075 0.91 1.573 13 375
Otago Dairy 50 230 Alluvial 0.075 0.03 0.8859 117 485
Otago Dairy 50 230 Alluvial 0.075 0.91 1.5487 14 382

Table 9: Scenarios based on measured data from the cadmium database (Contd)

  Farm type Fertiliser Rate (kg P /ha/y) Fertiliser Cd (mg/kg P) Soil Group sample depth (m) initial Cd (mg/kg) Cd at +100 years (mg/kg) Years to reach 1 mg/kg Years to reach 3 mg/kg
Southland Dairy 50 230 YGE 0.075 0.04 0.855 123 520
Southland Dairy 50 230 YGE 0.075 0.62 1.2561 59 455
Southland Dairy 50 230 YBE 0.075 0.04 0.9345 110 472
Southland Dairy 50 230 YBE 0.075 0.62 1.3231 53 414
Southland Dairy 50 230 Alluvial 0.075 0.04 0.8896 117 485
Southland Dairy 50 230 Alluvial 0.075 0.62 1.2936 55 423
Taranaki Dairy 50 230 YBL 0.075 0.04 1.2019 79 338
Taranaki Dairy 50 230 YBL 0.075 1.7 2.4704 0 181
Taranaki Dairy 50 230 Peat 0.075 0.04 1.6322 54 224
Taranaki Dairy 50 230 Peat 0.075 1.7 2.8235 0 119
Waikato Dairy 50 230 YBL 0.075 0.03 1.1987 80 338
Waikato Dairy 50 230 YBL 0.075 2.52 3.1559 0 74
Waikato Dairy 50 230 Peat 0.075 0.03 1.6291 54 224
Waikato Dairy 50 230 Peat 0.075 2.52 3.4652 0 48
Waikato Dairy 50 230 BGCL 0.075 0.03 1.0977 89 378
Waikato Dairy 50 230 BGCL 0.075 2.52 3.0933 0 83
Waikato Dairy 50 230 YBP 0.075 0.03 1.2089 79 331
Waikato Dairy 50 230 YBP 0.075 2.52 3.1734 0 72
Waikato Dairy 50 230 Alluvial 0.075 0.03 0.8859 117 485
Waikato Dairy 50 230 Alluvial 0.075 2.52 2.9855 0 104
Wellington Dairy 50 230 YGE 0.075 0.05 0.8587 123 519
Wellington Dairy 50 230 YGE 0.075 0.9 1.5023 16 413
Wellington Dairy 50 230 Alluvial 0.075 0.05 0.8935 116 484
Wellington Dairy 50 230 Alluvial 0.075 0.9 1.5398 15 383
Wellington Dairy 50 230 YBE 0.075 0.05 0.9381 109 461
Wellington Dairy 50 230 YBE 0.075 0.9 1.5643 15 377
Westland Dairy 50 230 YBE 0.075 0.04 0.9345 110 472
Auckland sheep/beef 30 230 YBE 0.075 0.03 0.5888 211 955
Auckland sheep/beef 30 230 YBE 0.075 1.1 1.4296 0 715
Auckland sheep/beef 30 230 BGCL 0.075 0.03 0.6893 168 743
Auckland sheep/beef 30 230 BGCL 0.075 1.1 1.5164 0 554
Bay of Plen sheep / beef 30 230 YBE 0.075 0.05 0.5955 210 953
Bay of Plen sheep / beef 30 230 YBE 0.075 1.6 1.894 0 560
Bay of Plen sheep / beef 30 230 Gley 0.075 0.05 0.6456 184 805
Bay of Plen sheep / beef 30 230 Gley 0.075 1.6      
Bay of Plen sheep / beef 30 230 YBL 0.075 0.05 0.7534 148 663
Bay of Plen sheep / beef 30 230 YBL 0.075 1.6 2.016 0 386

Table 9: Scenarios based on measured data from the cadmium database (Contd)

  Farm type Fertiliser Rate (kg P /ha/y) Fertiliser Cd (mg/kg P) Soil Group sample depth (m) initial Cd (mg/kg) Cd at +100 years (mg/kg) Years to reach 1 mg/kg Years to reach 3 mg/kg
Bay of Plen sheep / beef 30 230 YBP 0.075 0.05 0.7687 144 629
Bay of Plen sheep / beef 30 230 YBP 0.075 1.6 2.0373 0 363
Bay of Plen sheep / beef 30 230 Alluvial 0.075 0.05 0.5917 206 872
Bay of Plen sheep / beef 30 230 Alluvial 0.075 1.6 1.9195 0 495
Canterbury sheep/beef 30 230 YGE 0.075 0.01 0.5469 229 989
Canterbury sheep/beef 30 230 YGE 0.075 0.89 1.2179 33 793
Canterbury sheep/beef 30 230 Alluvial 0.075 0.01 0.5771 210 876
Canterbury sheep/beef 30 230 Alluvial 0.075 0.089 1.2538 30 696
Gisborne sheep / beef 30 230 YBE 0.075 0.05 0.5955 210 953
Gisborne sheep / beef 30 230 YBE 0.075 0.27 0.7077 181 924
Gisborne sheep / beef 30 230 Alluvial 0.075 0.05 0.5917 206 872
Gisborne sheep / beef 30 230 Alluvial 0.075 0.27 0.7136 176 842
Hawkes Bay sheep/beef 30 230 YGE 0.075 0.05 0.5609 226 986
Hawkes Bay sheep/beef 30 230 YGE 0.075 0.63 0.9779 107 867
Hawkes Bay sheep/beef 30 230 Alluvial 0.075 0.05 0.5917 206 872
Hawkes Bay sheep/beef 30 230 Alluvial 0.075 0.63 1.0137 97 763
Hawkes Bay sheep/beef 30 230 YBE 0.075 0.05 0.5955 210 953
Hawkes Bay sheep/beef 30 230 YBE 0.075 0.63 0.9985 101 844
Hawkes Bay sheep/beef 30 230 YBP 0.075 0.05 0.7687 144 629
Hawkes Bay sheep/beef 30 230 YBP 0.075 0.63 1.1636 68 554
Manawatu sheep/beef 30 230 YGE 0.075 0.04 0.5572 227 987
Manawatu sheep/beef 30 230 YGE 0.075 0.9 1.2273 30 790
Manawatu sheep/beef 30 230 Alluvial 0.075 0.04 0.5878 207 873
Manawatu sheep/beef 30 230 Alluvial 0.075 0.9 1.2631 27 694

Table 9: Scenarios based on measured data from the cadmium database (Contd)

  Farm type Fertiliser Rate (kg P /ha/y) Fertiliser Cd (mg/kg P) Soil Group sample depth (m) initial Cd (mg/kg) Cd at +100 years (mg/kg) Years to reach 1 mg/kg Years to reach 3 mg/kg
Manawatu sheep/beef 30 230 YBE 0.075 0.04 0.5921 211 954
Manawatu sheep/beef 30 230 YBE 0.075 0.9 1.2445 29 772
Nelson-Mar sheep/beef 30 230 YGE 0.075 0.03 0.5536 228 988
Nelson-Mar sheep/beef 30 230 YGE 0.075 1 1.3208 0 760
Nelson-Mar sheep/beef 30 230 Alluvial 0.075 0.03 0.5841 208 874
Nelson-Mar sheep/beef 30 230 Alluvial 0.075 1 1.3566 0 667
Nelson-Mar sheep/beef 30 230 YBE 0.075 0.03 0.5888 211 955
Nelson-Mar sheep/beef 30 230 YBE 0.075 1 1.337 0 744
Northland sheep/beef 30 230 YGE 0.075 0 0.5438 230 990
Northland sheep/beef 30 230 YGE 0.075 0.67 1.0144 96 856
Northland sheep/beef 30 230 YBE 0.075 0 0.5798 214 957
Northland sheep/beef 30 230 YBE 0.075 0.67 1.0343 91 834
Northland sheep/beef 30 230 Alluvial 0.075 0 0.5138 210 877
Northland sheep/beef 30 230 Alluvial 0.075 0.67 1.0501 87 753
Northland sheep/beef 30 230 BGCL 0.075 0 0.6805 169 745
Northland sheep/beef 30 230 BGCL 0.075 0.67 1.1273 72 647
Otago sheep/beef 30 230 YGE 0.075 0.03 0.5536 228 988
Otago sheep/beef 30 230 YGE 0.075 0.91 1.2366 27 787
Otago sheep/beef 30 230 YBE 0.075 0.03 0.5888 211 955
Otago sheep/beef 30 230 YBE 0.075 0.91 1.2538 26 769
Otago sheep/beef 30 230 Alluvial 0.075 0.03 0.5841 208 874
Otago sheep/beef 30 230 Alluvial 0.075 0.91 1.2724 25 691
Southland sheep/beef 30 230 YGE 0.075 0.04 0.5572 227 987
Southland sheep/beef 30 230 YGE 0.075 0.62 0.9689 110 870

Table 9: Scenarios based on measured data from the cadmium database (Contd)

  Farm type Fertiliser Rate (kg P /ha/y) Fertiliser Cd (mg/kg P) Soil Group sample depth (m) initial Cd (mg/kg) Cd at +100 years (mg/kg) Years to reach 1 mg/kg Years to reach 3 mg/kg
Southland sheep/beef 30 230 YBE 0.075 0.04 0.5921 211 954
Southland sheep/beef 30 230 YBE 0.075 0.62 0.9896 103 847
Southland sheep/beef 30 230 Alluvial 0.075 0.04 0.5878 207 873
Southland sheep/beef 30 230 Alluvial 0.075 0.62 1.0046 99 766
Taranaki sheep/beef 30 230 YBL 0.075 0.04 0.7502 149 663
Taranaki sheep/beef 30 230 YBL 0.075 1.7 2.1065 0 363
Taranaki sheep/beef 30 230 Peat 0.075 0.04 1.038 96 404
Taranaki sheep/beef 30 230 Peat 0.075 1.7 2.3543 0 215
Waikato sheep/beef 30 230 YBL 0.075 0.03 0.747 150 664
Waikato sheep/beef 30 230 YBL 0.075 2.52 2.8488 0 150
Waikato sheep/beef 30 230 Peat 0.075 0.03 1.0348 96 404
Waikato sheep/beef 30 230 Peat 0.075 2.52 3.0699 0 87
Waikato sheep/beef 30 230 BGCL 0.075 0.03 0.6893 168 743
Waikato sheep/beef 30 230 BGCL 0.075 2.52 2.8153 0 168
Waikato sheep/beef 30 230 YBP 0.075 0.03 0.7621 145 630
Waikato sheep/beef 30 230 YBP 0.075 2.52 2.8713 0 140
Waikato sheep/beef 30 230 Alluvial 0.075 0.03 0.5841 208 874
Waikato sheep/beef 30 230 Alluvial 0.075 2.52 2.7834 0 188
Wellington sheep / beef 30 230 YGE 0.075 0.05 0.2609 226 986
Wellington sheep / beef 30 230 YGE 0.075 0.9 1.2273 30 790
Wellington sheep / beef 30 230 Alluvial 0.075 0.05 0.5917 206 872
Wellington sheep / beef 30 230 Alluvial 0.075 0.9 1.2631 27 694
Wellington sheep / beef 30 230 YBE 0.075 0.05 0.5955 210 953
Wellington sheep / beef 30 230 YBE 0.075 0.9 1.2445 29 772

Table 9: Scenarios based on measured data from the cadmium database (Contd)

  Farm type Fertiliser Rate (kg P /ha/y) Fertiliser Cd (mg/kg P) Soil Group sample depth (m) initial Cd (mg/kg) Cd at +100 years (mg/kg) Years to reach 1 mg/kg Years to reach 3 mg/kg
Westland sheep/beef 30 230 YBE 0.075 0.04 0.5921 211 954
Wellington sheep/beef 18 230 YBE 0.1 0.19 0.3228    
Wellington sheep/beef 18 230 YBE 0.075 0.14 0.3342

0.0002

    
Waikato sheep/beef 36 230 YBE 0.2 0.39 0.625

0.0002

 276  
Waikato sheep/beef 36 230 YBE 0.1 0.65 1.0744

0.0006

 82 645
Waikato sheep/beef 36 230 YBE 0.075 0.53 1.1024 0.0008 82 504
Waikato sheep/beef 36 230 YBL 0.2 0.68 0.9783 0.0004 108 908
Waikato sheep/beef 36 230 YBL 0.1 0.68 1.2635 0.0009 54 454
Waikato sheep/beef 36 230 YBL 0.075 0.8 1.5547 0.0015 26 326
Waikato Potato 45 175 BGLC 0.15 0.41 0.9879 0.0004 103 488
Waikato Dairy 34 230 YBE 0.2 0.49 0.588 0.0003 675  
Waikato Dairy 34 230 YBE 0.1 0.55 0.721 0.0007 308  
Waikato Dairy 30 230 YBE 0.2 0.49 0.5411 0.0003    
Waikato Dairy 30 230 YBE 0.1 0.55 0.63 0.0006    
Waikato Dairy 34 230 YBL 0.2 0.72 0.8279 0.0006 281  
Waikato Dairy 34 230 YBL 0.1 0.81 1.0023 0.0013 99  
Waikato Dairy 38 230 YBL 0.2 0.72 0.8935 0.0006 166  
Waikato Dairy 38 230 YBL 0.1 0.81 1.1297 0.0015 58  
Wellington Dairy 39 230 YBE 0.1 0.35 0.3839 0.0007 220  
Wellington Dairy 30 230 YBE 0.1 0.35 0.4933 0.0005    
Taranaki sheep/beef 36 230 YBL 0.1 0.37 0.9929 0.0007 102 501
Taranaki sheep/beef 36 230 YBL 0.075 0.75 0.75 0.0015 32 332
Taranaki Dairy 39 230 YBL 0.1 0.61 0.9935 0.0013 102  

Table 9: Scenarios based on measured data from the cadmium database (Contd)

  Farm type Fertiliser Rate (kg P /ha/y) Fertiliser Cd (mg/kg P) Soil Group sample depth (m) initial Cd (mg/kg) Cd at +100 years (mg/kg) Years to reach 1 mg/kg Years to reach 3 mg/kg
Taranaki Dairy 39 230 YBL 0.75 1.41 1.7668 0.0032 0 734
Taranaki Dairy 38 230 YBL 0.1 0.61 0.962 0.0013 112  
Taranaki Dairy 38 230 YBL 0.075 1.41 1.7248 0.0031 0 986
Southland sheep/beef 21 230 YGE 0.075 0.18 0.4152 0.0003 685  
Southland sheep/beef 21 230 YGE 0.1 0.31 0.4421 0.0002    
Southland sheep/beef 21 230 YBE 0.075 0.18 4147 0.0003 875  
Otago sheep/beef 21 230 YGE 0.1 0.23 0.3974 0.0002 894  
Otago sheep/beef 21 230 YGE 0.075 0.1 0.3853 0.0002 702  
Otago sheep/beef 21 230 YBE 0.075 0.11 0.3917 0.0003 890  
Northland sheep/beef 20 230 YBE 0.075 0.31 0.4494 0.0003    
Manawatu sheep/beef 18 230 YGE 0.2 0.15 0.2479 0.0001    
Manawatu sheep/beef 18 230 YGE 0.12 0.2 0.3159 0.0001    
Manawatu sheep/beef 18 230 YGE 0.075 0.16 0.3461 0.0002    
Manawatu sheep/beef 18 230 YBE 0.15 0.12 0.2591 0.0001    
Manawatu sheep/beef 18 230 YBE 0.075 0.27 0.3793 0.0003    
Manawatu sheep/beef 18 230 YBL 0.075 0.18 0.3905 0.0004    
Hawks Bay sheep/beef 20 230 YBP 0.075 0.31 0.5219 0.0005 586  
Hawks Bay sheep/beef 20 230 YBE 0.075 0.31 0.4494 0.0003    

The CalBal model indicated future soil cadmium concentrations would be higher under sheep/beef farming than under dairy farming after 100 years when both are under the same fertiliser regime (Figure 23), although dairy farming requires more fertiliser for optimal production than beef and sheep farming. Dairy farming was shown to lead to more accumulation of cadmium in soil than sheep/beef farming when both are receiving more typical levels of fertiliser (50 kg ha-1 y-1 for dairy and 30 kg ha-1 y-1 for sheep/beef) (Figure 24). The sedimentation losses used by the model are oversimplified as sedimentation losses are due to a range of factors including topography, soil type, leaching class and climate, not just farm type. Table 10 shows the variation in total suspended sediment (TSS) measurements for different land-uses, topography and soil type reported in 5 publications. It appears likely the sedimentation losses used by the model are overestimated for flat land and should be adjusted. In addition, the model gave no consideration to deposition of eroded sediment from steep land to flatter land, animal relocation of cadmium through faeces or land application of dairyshed effluent.

Table 10: Comparison of sediment yield for different landuses, topography and soil type

Site Name Farm Type Topography Soil type TSS (kg ha-1 y-1)
Whatawhata Research Centre1 Sheep & beef Mainly steep land Brown and Ultic Soils, patches of Allophonic Soils 600–3212
Toenepi1, 2 Dairy Rolling to flat Recent and Granular Soils 142
Purukohukohu1,3 Sheep & beef Moderately steep Pumice Soils 22
Moutere4 Pasture Moderately steep Brown Soils, some Recent, Podzols, Ultic, Melanic and Gley Soils 210, 320, 670, and 790
Moutere4 Forestry Moderately steep Brown Soils, some Recent, Podzols, Ultic, Melanic and Gley Soils 40
Big Bush4 Native Bush Moderately steep Brown Soils, some Recent, Podzols, Ultic, Melanic and Gley Soils 60–110
Pukekohe5 Cropping Rolling Granular Soils 490–56800
Whatawhata Research Centre6 Sheep & beef steep land (tread damaged soil) Brown Soils 1666
Whatawhata Research Centre6 Sheep & beef Easy contoured land (tread damaged soil) Allophonic Soils 714

1 Quinn & Stroud (2002)
2 Wilcock et al. (1999)
3 Cooper & Thomsen (1988)
4 Basher (2003)
5 Basher et al. (1997)
6 Nguyen et al. (1998)

Peat soils accumulated more cadmium than the other soil types, YBL, YBP and BGCL soils accumulated the next largest amount of cadmium while YBE, YGE and alluvial soils accumulated the least cadmium. Differences in cadmium accumulation were due to differences in the leaching losses and soil bulk densities used by the model. The importance of soil bulk density on soil cadmium concentrations is discussed in section 3.6. The model also showed cadmium levels in soils under dairy farms fertilised at 30 kg ha-1 y-1, to decrease in cadmium with time once soil cadmium exceeded about 1.3 mg kg-1 due to high sedimentation losses (900 kg ha-1 y-1). Figure 25 shows an example of this occurrence in a YBP soil under dairy farming with a fertiliser regime of 30 kg P ha-1y-1. The decrease should be further investigated to evaluate the accuracy of this prediction as it has implications for the long term sustainability of dairy farming.

Figure 23: Comparison of 100 years accumulation of cadmium, starting at Cd = 0 mg kg-1, by soil groups under dairy and sheep/beef farming (both 30 kg P ha-1y-1).

Figure 23: Comparison of 100 years accumulation of cadmium, starting at Cd = 0 mg kg-1, by soil groups under dairy and sheep/beef farming (both 30 kg P ha-1y-1).

Figure 24: Comparison of 100 years accumulation of cadmium, starting at Cd = 0 mg kg-1, by soil groups under dairy and sheep/beef farming (50 kg P ha-1 y-1 for dairy and 30 kg P ha-1 y-1 for sheep and beef).

Figure 24: Comparison of 100 years accumulation of cadmium, starting at Cd = 0 mg kg-1, by soil groups under dairy and sheep/beef farming (50 kg P ha-1 y-1 for dairy and 30 kg P ha-1 y-1 for sheep and beef).

Figure 25: Soil cadmium concentrations decreasing with time in YBP soil under dairy (30 kg P ha-1y-1).

Figure 25: Soil cadmium concentrations decreasing with time in YBP soil under dairy (30 kg P ha-1y-1).

Figure 26: Soil cadmium concentrations decreasing with increased sample depth for a YBE under dairy (30 kg P ha-1y-1).

The CalBal model showed increasing the sampling depth effectively diluted the cadmium concentration due to mixing (Figure 26) indicating cadmium is held in the upper part of the topsoil. Cropping soils are usually regularly tilled to 20 cm allowing mixing, while pastoral soils may not be tilled after the initial seeding.

Pastoral farming resulted in increased soil cadmium content in all regions and nationally (Table 11). The peat soils of the Waikato region showed the highest potential for cadmium accumulation. The regions with the highest present day soil cadmium content also have the highest potential to accumulate cadmium in the future.

Table 11: Soil cadmium range in 100 years time after pastoral farming compared with present range

Region Present Range (µg g-1) Range in 100 years assuming pastoral farming (µg g-1)
Auckland 0.03–1.10 0.59–1.88
Bay of Plenty 0.05–1.60 0.59–2.40
Canterbury 0.01–0.89 0.55–1.53
Gisborne 0.05–0.27 0.59–1.05
Hawkes Bay 0.05–0.63 0.56–1.59
Manawatu-Wanganui 0.04–0.9 0.56–1.56
Nelson-Marlborough 0.03–1.00 0.58–1.65
Northland 0–0.67 0.51–1.52
Otago 0.03–0.91 0.55–1.57
Southland 0.04–0.62 0.56–1.32
Taranaki 0.04–1.7 0.75–2.82
Waikato 0.03–2.52 0.58–3.47
Wellington 0.05–0.90 0.56–1.56
Westland – 0.59–0.93
National 0–2.52 0.55–3.47

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