**The Value of Tactical Adaptation to El Niño–Southern Oscillation for East Australian Wheat**

**Bangyou Zheng 1, Scott Chapman 1,2 and Karine Chenu 3,\***


Received: 6 August 2018; Accepted: 8 September 2018; Published: 11 September 2018

**Abstract:** El Niño–Southern Oscillation strongly influences rainfall and temperature patterns in Eastern Australia, with major impacts on frost, heat, and drought stresses, and potential consequences for wheat production. Wheat phenology is a key factor to adapt to the risk of frost, heat, and drought stresses in the Australian wheatbelt. This study explores broad and specific options to adapt wheat cropping systems to El Niño–Southern Oscillation, and more specifically, to the Southern Oscillation Index (SOI) phases ahead of the season (i.e., April forecast) in Eastern Australia, when wheat producers make their most crucial managemen<sup>t</sup> decisions. Crop model simulations were performed for commercially-grown wheat varieties, as well as for virtual genotypes representing possible combinations of phenology alleles that are currently present in the Australian wheat germplasm pool. Different adaptation strategies were tested at the site level, across Eastern Australia, for a wide range of sowing dates and nitrogen applications over long-term historical weather records (1900–2016). The results highlight that a fixed adaptation system, with genotype maturities, sowing time, and nitrogen application adapted to each location would greatly increase wheat productivity compared to sowing a mid-maturity genotype, mid-season, using current practices for nitrogen applications. Tactical adaptation of both genotype and managemen<sup>t</sup> to the different SOI phases and to different levels of initial Plant Available Water ('PAW & SOI adaptation') resulted in further yield improvement. Site long-term increases in yield and gross margin were up to 1.15 t·ha−<sup>1</sup> and AU\$ 223.0 ha−<sup>1</sup> for fixed adaptation (0.78 t·ha−<sup>1</sup> and AU\$ 153 ha−<sup>1</sup> on average across the whole region), and up to an extra 0.26 t·ha−<sup>1</sup> and AU\$ 63.9 ha−<sup>1</sup> for tactical adaptation. For the whole eastern region, these results correspond to an annual AU\$ 440 M increase for the fixed adaptation, and an extra AU\$ 188 M for the PAW & SOI tactical adaptation. The benefits of PAW & SOI tactical adaptation could be useful for growers to adjust farm managemen<sup>t</sup> practices according to pre-sowing seasonal conditions and the seasonal climate forecast.

**Keywords:** ENSO; Southern Oscillation Index; SOI; El Niño; La Niña; soil water; environment type; climate adaptation; managemen<sup>t</sup> practices; crop model; APSIM
