Morphological plasticity of root growth under mild water stress increases water use efficiency without reducing yield in maize

Qian Cai,Yang Liu,Zhe Zhang,Liangshan Feng,Jochem B Evers,Chen Feng,Yue Zhang,Jiaming Zheng,Wei Bai,Lizhen Zhang,Zhanxiang Sun,Ning Yang,Yulong Zhang

doi:10.5194/bg-14-3851-2017

Abstract

Abstract. A large yield gap exists in rain-fed maize (Zea mays L.) production in semi-arid regions, mainly caused by frequent droughts halfway through the crop-growing period due to uneven distribution of rainfall. It is questionable whether irrigation systems are economically required in such a region since the total amount of rainfall does generally meet crop requirements. This study aimed to quantitatively determine the effects of water stress from jointing to grain filling on root and shoot growth and the consequences for maize grain yield, above- and below-ground dry matter, water uptake (WU) and water use efficiency (WUE). Pot experiments were conducted in 2014 and 2015 with a mobile rain shelter to achieve conditions of no, mild or severe water stress. Maize yield was not affected by mild water stress over 2 years, while severe stress reduced yield by 56 %. Both water stress levels decreased root biomass slightly but shoot biomass substantially. Mild water stress decreased root length but increased root diameter, resulting in no effect on root surface area. Due to the morphological plasticity in root growth and the increase in root ∕ shoot ratio, WU under water stress was decreased, and overall WUE for both above-ground dry matter and grain yield increased. Our results demonstrate that an irrigation system might be not economically and ecologically necessary because the frequently occurring mild water stress did not reduce crop yield much. The study helps us to understand crop responses to water stress during a critical water-sensitive period (middle of the crop-growing season) and to mitigate drought risk in dry-land agriculture.

Highlights

Maize (Zea mays L.) is the most important crop globally, and a major food crop in north-eastern China with an average yield around 5.3 t ha−1 (Dong et al, 2017)
Due to the increasing probability of extreme climate events (IPCC, 2007), water stress for agricultural production is likely to increase in this region (Song et al, 2014; Yu et al, 2014) which is detrimental for crop photosynthesis and yield (Richards, 2000)
Mild water stress from maize jointing (V6) to filling stages (R3) did not significantly reduce maize grain yield. This is different from a previous report which claimed that maize yield is much more affected by water stress during the flowering stage than at other stages (Doorenbos et al, 1979)

Summary

Introduction

Maize (Zea mays L.) is the most important crop globally, and a major food crop in north-eastern China with an average yield around 5.3 t ha−1 (Dong et al, 2017). The yield gap to the potential of 10.9 t ha−1 is still large (Liu et al, 2012), mainly due to frequent summer droughts. The averaged total rainfall during the cropgrowing season can meet the requirements of rain-fed maize in the semi-arid north-east of China, the yearly and seasonal variations often cause droughts (mostly mild water stress) during summer, resulting in yield loss. Shortduration water deficit during the rapid vegetative growth period causes around 30 % loss in final dry matter

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