Thursday 4 February, 2016
Australian grain growers are planting their winter crops a month earlier than three decades ago, according to survey results released by the Australian Export Grains Innovation Centre (AEGIC).
The results are being presented for the first time in a book chapter entitled “Innovations in dryland agriculture in Australia” co-authored by Doctors David Stephens, Wal Anderson and Kadambot Siddique which will appear soon in an overview book on agricultural innovation.
“Between 1978 and 2014 the mean midpoint of national wheat sowing shifted from around 10 June in the late 1970s and early 1980s to 10 May in 2014, the earliest recorded midpoint,” AEGIC Agro-Meteorologist Dr David Stephens said.
The findings came from an analysis of 168 sowing date survey forms of growers spread across Australia between 1978 and 1990 in a GRDC funded PhD project, and the mean midpoint of 233-613 paddocks monitored by the Birchip Cropping Group (BCG) Yield Prophet programme.
“The combination of zero tillage technology – which includes chemical spraying of weeds and faster seeding equipment – and grain varieties that perform better with early sowing, has enabled this major shift in farming practice,” Dr Stephens said.
“Formerly farmers would plough the ground, wait for the weeds to germinate, then plough the soil again before seeding with a third pass, using a lot more fuel in the process.
“In the last two years excellent opening rains in April and May meant many farmers were sowing wheat in a single pass from as early as mid-April and had their seeding programmes finished in early May.
“This early sowing, in combination with more nitrogen fertiliser, meant yields in many regions turned out much better than expected given the dry El Niño spring finishes to the two seasons.”
Dr Stephens said this innovation was a major contributor to growers increasing their profitability and doubling their crop water use efficiency over that time.
“This is because early sowing enables the crop growing window to shift to a period with a lower evaporative demand compared to late spring when evaporation rises rapidly and hot temperatures can reduce yields in grainfilling,” he said.
“In addition, early sowing enables better plant germination in warmer soils, better plant absorption of solar radiation, a reduced tendency for small plants to be affected by waterlogging, and better weed management options.”
“With earlier sowing and warmer temperatures hurrying crop growth, grain receival points are now opening much earlier, and as an example, the CBH bin at Merredin in Western Australia has moved its opening date from around 22 November in the early 1970s to an average around 18 October over the last four years.”
“This innovation in farming systems has been a lifesaver for growers battling a 5-30% decrease in growing season rainfall since the 2000s and it is fortunate that we don’t have such a fixed window to plant growth like in Canada where the growing season is more determined by snow cover”.
Dr Stephens said the analysis also highlighted that simple yield forecasting models based on rainfall summations could become inaccurate without taking into account the changed growing season, and that proper water balance models – like those used in AEGIC and in the Yield Prophet programme – should be utilised.
“The GRDC has continued to invest significantly to assist growers to increase yield and maximise WUE,” he said.
Key findings lately have emphasised that further gains in yield can be made in certain districts by planting even earlier with long-season varieties with long coleoptile length, so the trend to earlier sowing at a regional scale has not finished yet.
“The two challenges to these changes is the marked decline in May rainfall which is putting real pressure on early sowing opportunities and plant survival, and the continued irregular occurrence of frosts in southern districts which can affect early sown crops more.
“Overall, this major change in crop practice is helping build resilience to climate variability and is a key strategy in mitigating the effects of climate change.”