Speaker
Description
Introduction
Australia is renowned for being a hot, dry and water limited crop production zone. However, parts of the Australian high rainfall zones (HRZ) have a growing season water supply that can in theory support yields greater than reported record yields globally. The physiological basis underpinning higher yields in these regions are relevant to a global audience aiming to raise the yield frontier. Potential yield benchmarking is an important and established method to assess yield gaps and productivity. The relationship between temperature and radiation in the critical period for yield formation, defined as the photothermal quotient (PTQ), has been demonstrated to be an accurate predictor of potential yield in wheat (Fischer, 1985; Rawson, 1987). However, the relationship between yield and PTQ in the critical period for barley and recently identified critical period for canola (Kirkegaard et al., 2018) has received less attention. In addition, these relationships have not been defined for new wheat cultivars, nor for novel farming systems such as spring sowing of barley (versus traditional autumn sowing), modern canola cultivars (hybrids) and the most recent crop management practices. Our objective was to compile data from high-yielding canola (> 5 t/ha) and cereal (>8t/ha) crops in Australian irrigated and HRZ crops to explore the relationship between temperature and radiation (PTQ) in the critical period on yield potential and determine which management practices influence growth in the critical period. We sought to determine the frequency with which PTQ was likely to limit yield relative to water and N supply under current management practices and to explore the relationship between PTQ and water supply on yield when other agronomic factors are not limiting. We focussed on the Australian HRZ (> 400 mm growing season rainfall), to make comparisons to other high production areas internationally in Europe, South America, and New Zealand.
Materials, Methods:
We compiled data from a series of cereal and canola agronomic experiments conducted across Australia’s HRZ from 2016 -2023. The data included phenology, biomass, yield and yield components as well as water and N supply, temperature, and radiation in the critical period. Relationships between PTQ in the critical period and yield were compared with simple and accessible seasonal potential yield calculators such as that developed by French and Schultz (1984) for water-limited yield, and more sophisticated daily timestep models such as APSIM (Holzworth et al., 2014).
Results:
Our extensive dataset reported yields greater than 6t/ha for canola and up to 17t/ha for wheat. These new insights revealed that the relationship between PTQ in the critical period and potential yield required updating for recent wheat cultivars and management. A modified equation could be used to provide a reliable estimate of barley and canola potential yield based on the highest yielding canola and barley crops in Australia’s high rainfall zone. These relationships held up well when expanded to commercial crops, including a record 7.2 t/ha canola in Oberon NSW, and cereals including world record crops reported in NZ and Europe approaching 18t/ha. In such high rainfall environments, the relationship between water supply and yield were less reliable determinants of yield potential. Highest yields came from a combination of higher biomass and higher harvest index suggesting the environmental drivers of these traits were favourable in the critical period.
Discussion
Our data reveals yield comparable to the highest recorded global yields are achievable in some parts of Australia, despite the national average well below other high production regions. Our data demonstrate that actual and yield potential > 6t/ha in canola, and >10t/ha in cereals, well above the national Australian average, are frequent and could be achieved in the HRZ with appropriate crop management to optimise the PTQ in the critical period. This provides a framework for improvement for growers, agronomists and breeders to re-consider temperature and radiation in the critical period as drivers of yield potential. A future focus for research could consider biomass accumulation and allocation during the critical period to improve yield further.
References:
| Keywords | Yield; potential; radiation; temperature; management |
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