Climatic and agronomic conditions

​​Australian Crop Report: September edition

During August 2019, rainfall was generally average in central and southern cropping regions in Western Australia, southern cropping regions in Victoria, south-eastern South Australia, and northern cropping regions in Queensland (Map 1). Rainfall was well below average to below average across New South Wales and remaining areas in Victoria, South Australia, Queensland and Western Australia.

Map 1 Australian rainfall percentiles, 1 to 31 August 2019

 

Note: Rainfall percentiles are displayed for cropping regions only.
Source: Bureau of Meteorology

During late autumn and winter (May to August), rainfall totals in most southern cropping regions in Queensland and central and northern cropping regions in New South Wales were up to 150 millimetres lower than average, with vast areas recording between 25 and 50 millimetres over the past four months (Map 2). In contrast rainfall totals in large parts of southern cropping regions in Victoria were up to 100 millimetres higher than average. Rainfall totals of between 100 and 200 millimetres in parts of southern New South Wales, South Australia, Western Australia and the remainder of Victoria were average or slightly below average.

Map 2 Australian rainfall totals, 1 May to 31 August 2019

Note: Rainfall totals are displayed for cropping regions only.
Source: Bureau of Meteorology

Map 3 shows the relative levels of modelled root zone (0 to ~1 metres) soil moisture for cropping zones across Australia in August 2019. Soil moisture estimates are relative to the historical long-term average (1911 to 2015) and presented in percentiles.

Relative root zone soil moisture in August 2019 (Map 3) was extremely low to well below average in most cropping areas in New South Wales and Queensland and northern cropping regions in South Australia and Western Australia. In contrast, root zone soil moisture was average to above average in most cropping regions in Victoria, eastern South Australia and central Queensland. In the remaining parts of South Australia and Western Australia and central Queensland, root zone soil moisture was below average.

Map 3 Root zone soil moisture, August 2019

Note: Relative root zone soil moisture is displayed for winter crop growing regions only. The extremely high band indicates where the estimated soil moisture level for August 2019 fell into the wettest 10 per cent of estimated soil moisture levels on that day each year between 1910 and 2015. The extremely low band indicates where the estimated soil moisture levels for August 2019 fell into the driest 10 per cent of estimated soil moisture levels on that day between 1910 and 2015.
Source: Bureau of Meteorology.

According to the latest three-month rainfall outlook (September to November), issued by the Bureau of Meteorology on 29 August 2019, there is no strong tendency towards higher or lower than average spring rainfall in most cropping regions in Western Australia. In other states the chance of exceeding median rainfall is quite low. However, this does not mean large areas of eastern Australia will not receive any rainfall during spring.

It is highly likely there will be enough early spring rainfall to sustain crops through to harvest in regions where crops were in a strong position at the start of spring. There is a 75% chance of receiving between 25 and 100 millimetres in most southern cropping regions in Victoria and South Australia between September and October 2019 (Map 4). There is a similar probability of receiving between 25 and 100 millimetres in south eastern cropping regions in New South Wales and in southern and western cropping regions in Western Australia.

In most cropping regions in Queensland and New South Wales, and some cropping regions in Victoria, South Australia and Western Australia, there is a 75% chance of receiving between 2 and 25 millimetres. In regions with low levels of soil moisture, low early spring rainfall totals are unlikely to be sufficient to sustain crop production through to harvest.

The outlook for temperatures during spring indicates hotter than average daytime temperatures are likely across all winter cropping regions. Night-time temperatures are likely to be hotter than average in cropping regions in central and northern New South Wales, Queensland and Western Australia.

Map 4 Rainfall totals that have a 75% chance of occurring, September to October 2019

Note: Rainfall outlook is displayed for cropping regions only.
Source: Bureau of Meteorology

Map 5 shows modelled water availability levels that have a 75% chance of occurring by the end of October 2019. Water available for crop growth comes from water stored at sowing time and in-crop rainfall. On average, the total water requirement to achieve the national 5-year average wheat yield of 2.0 tonnes/ha is 235 millimetres, based on a conversion rate of 16kg of wheat per millimetre of water. The total water requirement to achieve 1.5 tonnes/ha, 1.0 tonnes/ha and 0.5 tonnes/ha based on this same conversion rate have been estimated to be 205, 175 and 140 millimetres, respectively.

ABARES estimated the winter cropping areas likely to achieve 235, 205, 175 and 140 millimetres of water availability. These indicative estimates is based on modelled plant available soil moisture as at 30 April 2019, recorded rainfall totals as at 31 August 2019 and an estimate of rainfall totals with a 75% chance of falling for September and October derived from the Bureau of Meteorology latest rainfall outlook released on 29 August 2019.

The crop yield associated with a specific level of water availability varies across regions with variations in soil characteristics. The indicative estimates presented above, abstract from this complexity by assuming a conversion rate of 16kg of wheat per millimetre of water and a standard soil evaporation loss factor of 110 millimetres. As a result the implications of the analysed threshold values of water availability may be quite different across regions. Additionally, in some seasons the responsiveness of crop growth to water availability will be better than average (around 22kg/mm) and in other years it will be worse (around 6kg/mm) as responsiveness depends on factors such as temperature, humidity, soil nutrition and the timing of rainfall.

Map 5 Modelled water availability levels that have a 75% chance of occurring by the end of October 2019

 

Note: Modelled water availability is displayed for cropping regions only.
Source: ABARES & Bureau of Meteorology

At the end of August 2019, there was a 75% chance of achieving at least 235 millimetres of water availability by the end of October 2019 in cropping region in southern Victoria, central and southern South Australia and western and southern Western Australia. Across part of southern New South Wales and much of the remainder of Victoria, South Australia and Western Australia there is a 75% chance of achieving between 140 and 205 millimetres of water availability by the end of October 2019.

Table 4 Rainfall in major cropping districts, median and actual, June 2019 to August 2019
DistrictDistrict no. June median
mm
June 2019
mm
July median
mm
July 2019
mm
August median
mm
August 2019
mm
New South Wales
NW Plains (W)52 33 6 29 8 19 1
NW Plains (E)53 36 11 35 12 30 1
NW Slopes (N)54 38 15 41 9 37 2
NW Slopes (S)55 43 14 41 16 40 5
N Tablelands (N)56 43 22 44 10 42 6
CW Plains (S)50 37 17 36 12 30 7
CW Plains (N)51 33 5 28 6 23 2
CW Slopes (N)64 39 11 44 9 35 7
CW Slopes (S)65 47 25 50 13 45 12
C Tablelands (N)62 41 15 45 7 44 9
C Tablelands (S)63 53 39 56 19 58 17
Riverina (W)75 32 21 30 26 32 9
Riverina (E)74 44 32 40 35 43 13
SW Slopes (N)73 57 41 59 27 61 20
SW Slopes (S)72 92 70 102 84 114 54
Victoria
N Mallee76 26 24 28 26 30 12
S Mallee77 33 43 33 35 36 20
N Wimmera78 42 62 42 44 43 34
S Wimmera79 58 71 64 64 65 47
Lower North80 40 40 40 43 39 20
Upper North81 54 57 55 44 52 29
Lower North East82 107 88 113 97 118 63
North Central88 80 101 83 66 85 67
Western Plains89 57 78 60 67 67 61
West Coast90 85 93 90 108 93 76
Queensland
Central Highlands35 27 21 16 14 12 7
Maranoa43 25 8 22 6 19 3
W Darling Downs42 27 17 28 3 19 3
E Darling Downs41 29 20 31 2 24 2
Moreton S Coast40 37 44 36 11 28 5
South Australia
Upper South East25B 50 52 53 46 56 44
Murray Mallee25A 31 41 30 30 35 19
Murray River24 28 28 26 19 30 17
East Central23 73 71 76 55 74 58
Yorke Peninsula22A 53 48 57 37 54 30
Lower North21 43 49 43 25 47 29
Upper North19 26 32 26 9 26 9
Western Agricultural18 30 25 29 10 28 14
Western Australia
North Coast8 70 104 65 39 48 20
Central Coast9 142 172 141 85 113 71
Northern Central10 53 77 50 35 43 21
South Central10A 56 66 59 38 52 38
South East12 19 24 18 8 16 12

​​Note: Displayed for major cropping districts only. See table 4 for district names and observed district rainfall.
Source: Bureau of Meteorology.

Map 6 Rainfall districts, Australia

 

Note: Displayed for major cropping districts only. See table 4 for district names and observed district rainfall.
Source: Bureau of Meteorology.

Statistical tables​​

Last reviewed: 4 November 2019
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