Earlier crop flowering caused by global warming alleviated by irrigation

Abstract

Ensuring that crops flower within an optimal window minimises long-term risk of abiotic stress exposure, improving prospects for attaining potential yield. Here we define the optimal flowering period (OFP) as the calendar time in which long-term risk of frost, water and heat stress are collectively minimal. Using the internationally-renowned farming systems model APSIM, we characterised effects of climate change and extreme climatic events on the OFPs of barley, durum wheat, canola, chickpeas, fababean and maize from 1910 to 2021. We generated response surfaces for irrigated and dryland conditions using a range of representative sowing times for early and late maturity genotypes. Global warming truncated crop lifecycles and shifted forward flowering of winter crops by 2-43 days in dryland environments and by -6 -19 days in environments with irrigation. Relief from water stress by irrigation delayed OFPs by 3-25 days or 11-30 days for early and late maturity winter crops, respectively, raising average yields of irrigated crops by 44%. Even so, irrigation was unable to completely negate the long-term yield penalty caused by the climate crisis; yields within OFPs declined by 24% and 13% for rainfed and irrigated crops over the 111-year simulation duration. We conclude with two important insights: (1) use of irrigation broadens OFPs, providing greater sowing time flexibility and likelihood of realising potential yields compared with dryland conditions and (2), the most preferable maturity durations for irrigated winter and summer crops to maximise potential yields are early-sown long-season (late) and later-sown short-season (early) maturity types, respectively.

Whole farm planning raises profit despite burgeoning climate crisis

“…Thus, irrigation mitigates the extent to which development is increased as the climate warms and consequently the longer crop growing cycle allows greater biomass production and seed set. This result is analogous to findings of Schauberger et al 76 , and Muleke et al 11 . Our study also found that yield reductions were higher in the low rainfall ('dry and hot') regions of Griffith (41%) and Kerang (39%, Figs.…”

“…The length of the optimal flowering window varied between crop genotypes under irrigation and rainfed conditions across sites (Tables 5, S1, S2, S3 and S4). Generally, irrigation extended the OFP window compared with dryland crops, particularly for the late winter genotypes, consistent with findings by Muleke et al11 . The latest OFP was at Hagley for irrigated late winter genotypes of canola (25 September), chickpea (4 October), spring barley (5 November) and durum wheat (12 November).…”

“…Optimal flowering periods (OFP) for each site were computed as the flowering dates corresponding to ≥ 95% of the maximum 15-day running mean frost-heat yield (FHY), following 53 and Liu et al 54 . FHY represents simulated yields accounting for biological impacts of suboptimal (frost) and supraoptimal (heat) stress following Liu et al 53 , Liu et al 54 , and Muleke et al 11 ; table reproduced in the supplementary information for clarity (Table S10).…”

“…Previous studies have demonstrated trade-offs between the potential crop yield, commodity prices, variable costs and water use in determining crop profits 8,9 . For example, high yield per unit area (e.g., cotton bales per hectare) can offset high water-use and variable costs resulting in greater crop profit, whereas high commodity prices (e.g., mungbean prices) can sustain high returns on irrigation investments, despite low crop yield per hectare 10,11 . While commodity prices govern profitability for many rainfed farm businesses 12,13 , water price and use on irrigated farms may have a dominating influence on profitability compared with other variable costs 14 .…”

Sustainable intensification with irrigation raises farm profit despite climate emergency

“…Past work on agronomic adaptation to climate change has primarily focused on field‐scale interventions such as changes to management and/or genotype/crop type combinations to improve yield (Ibrahim et al, 2019; Langworthy et al, 2018; Liu et al, 2021; Liu, Harrison, Hunt, et al, 2020) such as that aimed at closing yield gaps (Angella et al, 2016; Bryan et al, 2014; Liu et al, 2015, 2022; Muleke, Harrison, de Voil, et al, 2022; Pradhan et al, 2015). However, higher crop yields do not necessarily translate to higher crop profitability, because above a certain level of inputs, the rate of return from increased inputs diminishes (Ibrahim et al, 2018).…”