Climate trends account for stalled wheat yields in Australia since 1990

Abstract

Global food security requires that grain yields continue to increase to 2050, yet yields have stalled in many developed countries. This disturbing trend has so far been only partially explained. Here, we show that wheat yields in Australia have stalled since 1990 and investigate the extent to which climate trends account for this observation. Based on simulation of 50 sites with quality weather data, that are representative of the agro-ecological zones and of soil types in the grain zone, we show that water-limited yield potential declined by 27% over a 26 year period from 1990 to 2015. We attribute this decline to reduced rainfall and to rising temperatures while the positive effect of elevated atmospheric CO concentrations prevented a further 4% loss relative to 1990 yields. Closer investigation of three sites revealed the nature of the simulated response of water-limited yield to water availability, water stress and maximum temperatures. At all three sites, maximum temperature hastened time from sowing to flowering and to maturity and reduced grain number per m and average weight per grain. This 27% climate-driven decline in water-limited yield is not fully expressed in actual national yields. This is due to an unprecedented rate of technology-driven gains closing the gap between actual and water-limited potential yields by 25 kg ha yr enabling relative yields to increase from 39% in 1990 to 55% in 2015. It remains to be seen whether technology can continue to maintain current yields, let alone increase them to those required by 2050.

Agronomic Practices for Reducing Wheat Yield Gaps: A Quantitative Appraisal of Progressive Producers

“…Mean wheat Y a in our database was very similar to these long-term estimates and was considerably greater than state-or county-level yields (Patrignani et al, 2014). Regions characterized by similar Y w include India (3.5 < Y w < 7 Mg ha −1 ; Aggarwal et al, 1994), Russia (4.3 < Y w < 5.6 Mg ha −1 , Schierhorn et al, 2014), Australia (4.9 < Y w < 5.3 Mg ha −1 , Hochman et al, 2017), Spain (6.1 < Y w < 7.1 Mg ha −1 , Abeledo et al, 2008), and China (Y w ? Regions characterized by similar Y w include India (3.5 < Y w < 7 Mg ha −1 ; Aggarwal et al, 1994), Russia (4.3 < Y w < 5.6 Mg ha −1 , Schierhorn et al, 2014), Australia (4.9 < Y w < 5.3 Mg ha −1 , Hochman et al, 2017), Spain (6.1 < Y w < 7.1 Mg ha −1 , Abeledo et al, 2008), and China (Y w ?…”

“…Identifying management practices that contribute to increased grain yield can reduce wheat Y G in regions characterized by yield stagnation (Hochman et al, 2017). The use of replicated research trials where different treatments are imposed on the crop (e.g., Jaenisch et al, 2018) is the most common approach to identify opportunities to reduce the Y G (Grassini et al, 2015); however, these are costly and impracticable at a large scale (van Ittersum et al, 2013).…”

Australian wheat production expected to decrease by the late 21st century

“…Global wheat production with CO 2 fertilization was approximately 20% and 35% higher by 2050s and 2090s, respectively, compared to estimates that assumed climate change without CO 2 fertilization (Balkovič et al., ). However, in almost all Australian states, the negative effects of increased temperatures and reduction in rainfall on wheat are not fully compensated for by the positive effects of increased CO 2 concentrations (Hochman, Gobbett, & Horan, ). This highlights the need for adaptation plans to cope with climate change.…”

Crops, Nitrogen, Water: Are Legumes Friend, Foe, or Misunderstood Ally?

“…Analyses of the 'water footprint' of legumes and other crops emphasizes that there are significant gains to be made (increasing production per unit of water consumed) through better understanding of fundamental aspects of plant biology and its management (e. g., [105]). While there is little evidence of a global increase in drought over the past 60 years [106], there is good evidence of changing amounts and seasonal distribution of rainfall in many of the world's most important grain cropping areas (e.g., in USA [107]), and that this is already reducing crop yields in drier areas (e.g., in Australia [108]). Furthermore, projections of future climates strongly suggest an increase in drought in many regions [109].…”