The important but weakening maize yield benefit of grain filling prolongation in the US Midwest

Authors: ZHU, PENG - Purdue University; JIN, ZHENONG - Purdue University; ZHUANG, QIANLAI - Purdue University; CIAIS, PHILIPPE - Laboratoire Des Sciences Du Climat Et De L'Environnement (LSCE); Bernacchi, Carl; WANG, XUHUI - Laboratoire Des Sciences Du Climat Et De L'Environnement (LSCE); MAKOWSKI, DAVID - Institute Of Plant Sciences Paris-Saclay; LOBELL, DAVID - Stanford University

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2018
Publication Date: 9/26/2018
Citation: Zhu, P., Jin, Z., Zhuang, Q., Ciais, P., Bernacchi, C.J., Wang, X., Makowski, D., Lobell, D. 2018. The important but weakening maize yield benefit of grain filling prolongation in the US Midwest. Global Change Biology. 24:4718-4730. https://doi.org/10.1111/gcb.14356.
DOI: https://doi.org/10.1111/gcb.14356

Interpretive Summary: To understand how best to increase crop productivity to meet growing demands for food, fuel, feed, fiber, and all other agricultural uses, it is important to understand how crops response to past and current environmental conditions. Recent improvements in corn production have been linked to a number of possible breeding strategies, however, there is a lot of uncertainty regarding what the major determining factors for crop improvement may be. In this experiment, we use a model to disentangle the major reasons why corn improvements have been occurring in recent history. We used satellite data with crop yield reports to show that over the last 16 years the grain filling period, defined as the time needed to fully ‘fill’ the corn grain kernels with starch, has been increasing at a rate of one extra day every three years. However, data from excessively warm counties show that the rate of yield increase with longer grain filling period is less than in cooler counties. The results from this study show that a shift toward varieties with longer grain filling periods has a much greater contribution to higher yields than previously thought. The modeling component of this study suggests that if breeding continually increases the time corn plants stay in the grain filling stage, yield losses in the future could be lower. But this only is likely to occur in the absence of extreme heat waves and droughts.

Technical Abstract: A better understanding of recent crop yield trends is required for sustaining the yield progress and maintaining food security. Several possible mechanisms have been investigated recently in order to explain the steady growth in maize yield over the US Corn-Belt, but a substantial fraction of the increasing trend remains elusive. In this study, we argue that shift towards longer varieties with prolonged grain filling period (GFP) had a much greater contribution to the recent yield trends than previously thought. By using long term satellite data from 2000 to 2015, we identified an average lengthening of GFP of 0.37 days per year over the region, which probably results from variety renewal. An empirical statistical model demonstrated that longer GFP contributed roughly one-quarter (23%) of the yield increase trend by promoting kernel dry matter accumulation, yet less yield benefit was identified in hotter counties. Both official survey data and crop model simulations estimated a similar contribution of GFP trend to yield. If growing degree days that determines the GFP continues to prolong at the current rate for the next 50 years, yield reduction will be lessened with 25% and 18% longer GFP under Representative Concentration Pathway 2.6 (RCP 2.6) and RCP 6.0, respectively. However, this level of progress is insufficient to compensate yield losses in future climates, because drought and heat stress during the GFP will become more prevalent. Our study highlights devising multiple effective adaptation strategies is necessary to withstand the upcoming challenges in food security.