Evaluating irrigated rice yields in Japan within the Climate Zonation Scheme of the Global Yield Gap Atlas

S Ishikawa,T Iizumi,T Nakashima,M C Hare

doi:10.1017/s0021859621000186

Abstract

AbstractThe Global Yield Gap Atlas (GYGA) is an international project that addresses global food production capacity in the form of yield gaps (Yg). The GYGA project is unique in employing its original Climate Zonation Scheme (CZS) composed of three indexed factors, i.e. Growing Degree Days (GDD) related to temperature, Aridity Index (AI) related to available water and Temperature Seasonality (TS) related to annual temperature range, creating 300 Climate Zones (CZs) theoretically across the globe. In the present study, the GYGA CZs were identified for Japan on a municipality basis and analysis of variance (ANOVA) was performed on irrigated rice yield data sets, equating to actual yields (Ya) in the GYGA context, from long-term government statistics. The ANOVA was conducted for the data sets over two decades between 1994 and 2016 by assigning the GDD score of 6 levels and the TS score of 2 levels as fixed factors. Significant interactions with respect to Ya were observed between GDD score and TS score for 13 years out of 21 years implying the existence of favourable combinations of the GDD score and the TS score for rice cultivation. The implication was also supported by the observation with Yg. The lower values of coefficient of variance obtained from the CZs characterized by medium GDD scores indicated the stability over time of rice yields in these areas. These findings suggest a possibility that the GYGA-CZS can be recognized as a tool suitable to identify favourable CZs for growing crops.

Highlights

The year 2020 was experienced as an unprecedented year all over the globe
We developed an alternative approach to deal with Climate Zonation Scheme (CZS) in order to overcome the relatively small geographical scale and mountainous topography of Japan as well as to utilize statistical information stored, mostly, on a municipality basis
Maps where the Global Yield Gap Atlas (GYGA) Climate Zones (CZs) are expressed on a municipality scale between the years 1993–2002 and 2005–2016 are shown in Figs 3(b) and (c), respectively

Summary

Introduction

The year 2020 was experienced as an unprecedented year all over the globe. As a response to the Covid-19 pandemic declared by the World Health Organization on 11th March, food export restrictions were imposed by several nations (Hepburn et al, 2020). An international project named Global Yield Gap Atlas (GYGA) initiated by Van Ittersum et al (2013) has been helping to provide the international community with the basic knowledge to address the issue of food security by adopting the simulation approach using crop models. In the GYGA project, the possibility for achieving the world’s food production capacity is expressed in the form of yield gaps (Yg), i.e. the difference between potential (Yp) and actual yields (Ya). What makes GYGA different from other yield gap studies (Sentelhas et al, 2015) is that its original Climate Zonation Scheme (CZS) was developed in the project (Van Wart et al, 2013) allowing it to be used on a global basis. The climate here is used in a conservative context in accordance with the definition ‘the weather conditions prevailing in an area in general or over a long period’ (Lexico Dictionaries, 2019)

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