1. Central

Introduction

Figure 1. Details and names of the GRDC agro-ecological zones used for reporting.

Table 1 Area of cultivation 1984 2001 Change (%) Agricultural area 16,681,565 16,351,516 -2.0 Grain crop area 1,186,735 1,460,068 23.0 Cereal area: 1,178,696 1,326,017 12.5 Cropping intensity (%) 7.1 8.9 25.5 Cereal proportion (%) 99.3 90.8 -8.6

1800000

NSW Central 1600000 NSW NorthEast-Qld SouthEast NSW NorthWest-Qld SouthWest 1400000 Qld Central

1200000

1000000

800000 Wheat area (ha) 600000

400000

200000

0

3 5 6 8 9 1 3 4 6 7 9 0 1 2 8 8 8 8 9 9 9 9 0 0 9 984 9 9 9 9 992 9 995 9 9 0 0 1 1 198 1 1987 1 1 1990 1 1 199 1 1 199 1 1998 1 2 200 2 Year of reporting

3 NSW Central NSW NorthEast-Qld SouthEast 2.5 NSW NorthWest-Qld SouthWest Qld Central

2

1.5 Wheat yield (t/ha) 1

0.5

0 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 Year of reporting

Figure 2. Trend in wheat area sown and yield harvested over 20 years for AEZs in GRDC northern region.

Figure 3 Variation across NSW central for grain yield trends a) wheat and b) barley.

Figure 4 Variation across NSW central for grain water use efficiency a) wheat and b) barley.

Figure 5. Distribution in available water capacity in a) layer 1 and b) layer 2 across the zone.

Figure 6. Variation in saturated hydraulic conductivity for a) layer 1 and b) layer 2 across the zone.

Figure 7. Variation in pH for a) layer 1 and b) layer 2 across the zone.

Figure 8. Variation in depth of soil in a) layer 1 and b) layer 2 across the zone.

Figure 9. Variation in bulk density for a) layer 1 and b) layer 2 across the zone.

Figure 10. Variation in soil texture for a) layer 1 and b) layer 2 across the zone.

Table 2. The area treated with lime, the amount and rate of application and percentage of agricultural land treated in 2001. Source ABS AgStats. NSW Central Zone Area Lime Rate of Percentage SLAs treated with equivalent application of total lime (ha) applied (t) (t/ha) land treated Bogan 87 140 1.61 0.007 Cobar 0 0 1.57 0.000 Lachlan 1,811 3,299 1.82 0.128 Carrathool 2,994 3,023 1.01 0.181 Griffith 2,923 4,781 1.64 1.884 Leeton 0 0 0.90 0.000 Murrumbidgee 737 1,687 2.29 0.686 Berrigan 1,019 1,281 1.26 0.555 3291 5,182 1.57 1.694 2,257 4,082 1.81 0.568 135 234 1.74 0.558 Murray 2,141 4,688 2.19 0.624 3,364 3,171 0.94 0.938 Windouran 2,228 651 0.29 0.299 0 0 0.78 0.000 Wentworth 0 0 0.33 0.000 Bogan 3 22 6.66 0.000 Total 22,991 32,241 1.40 0.141

Table 3. The area fertilised, the average rate of Nitrogen (N), Phosphorus (P) and Potassium (K) applied within Statistical Local Areas (SLA) in 2001. Source ABS AgStats.

NSW Central Zone Area N rate P rate K rate SLAs fertilised (ha) kg/ha kg/ha kg/ha Balranald 58,072 14.6 10.6 0.6 Berrigan 139,511 37.6 15.9 1.0 Bogan 160,616 14.7 13.2 0.2 Carrathool 385,322 25.4 12.6 0.5 Cobar 71,114 17.1 8.9 0.1 Conargo 118,700 38.9 15.0 0.7 Deniliquin 14,380 34.2 15.0 0.7 Griffith 129,120 56.9 13.5 1.1 Hay 30,920 84.7 13.9 0.1 Jerilderie 143,656 48.5 17.0 0.4 Lachlan 390,988 13.5 12.0 0.1 Leeton 67,734 59.4 15.0 1.3 Murray 125,927 29.3 14.2 0.4 Murrumbidgee 110,599 41.8 10.0 0.5 Wakool 150,479 29.4 13.3 0.7 Wentworth 41,162 23.5 10.7 4.8 Windouran 16,282 37.7 13.3 0.5 Total 2,154,582 30.2 13.13 0.6

Table 4. The percentage (%) of crop area that was sown without cultivation in 1996 and 2001 and the change between the two years within Statistical Local Areas. Source ABS AgStats. NSW Central Zone SLAs 1996 2001 Change Bogan 9.2 20.4 11.2 Cobar 4.4 4.3 -0.1 Lachlan 4.9 6.8 1.9 Carrathool 4.9 11.0 6.1 Griffith 9.7 15.7 6.0 Hay 1.9 9.3 7.4 Leeton 8.6 22.4 13.8 Murrumbidgee 6.6 9.8 3.3 Berrigan 7.7 35.3 27.6 Conargo 7.1 29.5 22.5 Deniliquin 1.1 25.0 23.9 Jerilderie 9.9 37.5 27.6 Murray 14.7 36.6 21.8 Wakool 6.0 8.2 2.3 Windouran 2.7 31.3 28.7 Balranald 4.4 4.3 -0.1 Wentworth 2.0 6.0 4.1 Average 6.2 14.8 8.6

Table 5. The proportion of total landholders (%) that observed salinity present, undertake some management for salinity, grow cereals, oilseed or pulse crops, apply fertiliser or lime on their holdings in 2001 by Statistical Local Area. Source ABS AgStats. Salinity Salinity Apply Apply NSW Central Zone SLAs present manage Cereal Oilseed Pulse fertliser lime Bogan 1 8 68 7 7 66 4 Cobar 1 5 34 3 0 32 1 Lachlan 6 20 87 8 7 84 6 Carrathool 10 33 81 20 24 85 14 Griffith 8 41 29 5 7 79 8 Hay 2 27 33 8 2 49 9 Leeton 15 41 49 10 5 85 10 Murrumbidgee 10 53 87 29 11 92 12 Berrigan 7 49 65 29 8 83 29 Conargo 7 55 75 25 1 90 24 Deniliquin 4 43 66 4 4 80 23 Jerilderie 8 56 86 38 5 92 27 Murray 7 48 79 26 14 82 39 Wakool 20 50 59 8 6 78 19 Windouran 4 45 77 12 0 83 10 Balranald 12 24 34 2 2 58 9 Wentworth 10 39 6 1 0 71 9 60 14 6 76 15

Potential gains from improving WUE Potential gains were estimated for individual SLAs were calculated in two ways based on improvements to wheat applying uniformly across all grains. The first reflects a targeted approach, with the amount of increased production of grain (from the maximum area sown to grain crops in the last 20 years) if yields were improved to bring water use efficiency to certain benchmark levels (i.e. they were not increased for those areas already achieving the benchmark). The second reflected a uniform improvement across the board by increasing water use efficiencies across the board by 10 percentage points (other increases will be simple multiples of this). The gains (Table 6) from the step up from 60% to 70% in average water use efficiency is much larger than from 50% to 60% because a larger area would be involved in achieving that target efficiency. Although the total gains for achieving a benchmark WUE and for increasing by 10% points give a different distribution across SLAs.

Table 6. Estimates of average annual production gains (tonnes) based on achieving benchmark water use efficiencies if the maximum grain area was sown to wheat. NSW Central Zone Benchmark Water use efficiencies (%) SLAs Now 50 60 70 +10 Bogan 0.36 72,739 124,696 176,653 18,704 Cobar 0.63 7,881 7,092 Lachlan 0.42 257,179 400,057 60,009 Carrathool 0.91 47,865 Griffith 0.79 13,056 Leeton 0.98 5,008 Murrumbidgee 0.79 9,431 Berrigan 0.69 2,222 15,332 Conargo 0.83 9,635 Deniliquin 0.76 1,057 Jerilderie 0.95 15,648 Murray 0.57 7,888 34,182 14,988 Wakool 0.57 10,708 46,402 20,345 Windouran 0.91 1,687 Balranald 0.63 9,445 8,500 Wentworth 0.84 5,854 Total 72,739 400,472 676,841 254,210

Contribution of some soil constraints The contributions of some soil constraints to grain production were estimated by making rough calculations using the soil parameters derived from the ASRIS data base using wheat as indicator crop. The area of a soil feature was derived for just the agricultural lands within the soil cropping zone (ie not all of each agro-ecological zone was estimated). The features in the ASRIS database considered most likely to limit wheat yield were soil acidity (pH), bulk density and permeability. Soil acidity (pH less than 5.5) was considered to reduce yield by reducing access to available water and assumed to be 12.5 mm in the topsoil, which at 20 kg/ha/mm meant a reduction in yield of 0.25 t/ha: for the subsoil it was assumed to be 10 mm for a reduction of 0.2 t/ha. The greater of the 2 values was used in the summary table. Bulk density greater than 1.4 g/cc (in the subsoil) was considered to reduce root penetration and access to 10 mm of water, which equated to 0.2 t/ha. Permeability or hydraulic conductivity was considered to reduce water infiltration when it was mainly in topsoil or to produce waterlogging if in the subsoil and the effect were assigned as 0.25 t/ha and 0.1 t/ha respectively. The greater of the two values was used in the Table 7.

Table 7. Estimates of the benefits (tonnes of grain) from overcoming some soil constraints derived from ASRIS on grain production in the Statistical Local Areas of the AEZ. Maximum area of grains sown in each area was used in the estimation. Bulk density Permeability Max area of NSW Central Zone SLAs pH <5.5 > 1.4 < 3mm/hr grain (ha) Bogan 5,274 4,349 5,297 164,074 Cobar 5,402 892 568 63,326 Lachlan 46,825 33,313 3,241 387,152 Carrathool 68,734 10,493 6,587 270,423 Griffith 629 6,085 1,330 46,627 Leeton 2,679 3,427 78 19,872 Murrumbidgee 5,850 5,176 460 36,273 Berrigan 5,813 13,036 0 67,841 Conargo 1,096 8,136 163 41,708 Deniliquin 0 1,124 49 5,622 Jerilderie 6,722 10,448 669 64,394 Murray 235 16,929 563 84,676 Wakool 11 15,240 11,221 118,287 Windouran 29 1,657 29 8,393 Balranald 175 9,964 2,536 66,930 Wentworth 0 6,056 2,038 47,596 Total 87,612 146,325 34,829 1,493,194