Abstract
Long-term trend of crop yields has been widely studied in global scales to find which crops and which geographic regions offer the best hope of meeting food demands, and which regions needed the most improvements. In this study, a mathematical method was applied to analyze spatial patterns in long-term temporal trends of three major crops’ yields in Japan archipelago. The changes in annual yields of rice, wheat, and soybean over a period of about 60 years in all 47 prefectures of Japan was analyzed by using the data of agricultural records. For all the three crops, the nationwide yields previously improved, but currently were stagnating in Japan. The result suggests that the annual yields were not improving in 53, 85, and 89% of those prefectures in Japan for rice, wheat, and soybean, respectively. The spatial patterns in temporal trends show that the percentage of number of yield-not-improving prefecture was higher in low latitude regions than high latitude regions. These results highlight the increasingly difficult challenge of meeting the growing demands and stagnating supplies in daily staple foods not only for agricultural scientists but also for Japanese society.
Highlights
Crop production in agriculture is directly related to food supply
The spatial patterns in temporal trends show that the percentage of number of yield-not-improving prefecture was higher in low latitude regions than high latitude regions
The long history of cultivation and the geographical variation of climatic conditions, such as the number of rainy days during cropping season, result in large spatial differences in crop yield (Lobell et al, 2009)
Summary
Crop production in agriculture is directly related to food supply. As a result, the crop yield must be increased to meet the growing demands (Alexandratos, 1999; Cassman, 1999; Glover et al, 2012; Tilman et al, 2002) driven by the increasing human population, meat consumption, and biofuel use (Foley et al, 2011; Godfray et al, 2010; Holdren & Ehrlich, 1974; Pingali, 2006; Tilman et al, 2011). Some reports have suggested that those crop yields may be stagnating or declining in many important global croplands (Brisson et al, 2010; Cassman, 1999; Finger, 2010; Hafner, 2003; Kendall & Pimentel, 1994; Peltonen-Sainio et al, 2009), in particular for three key crops – maize, rice, and wheat (Tilman et al, 2011). The yields were reported that either never improved, stagnated, or collapsed across 24–39% of maize-, rice-, wheat-, and soybean-growing areas including the most important cropland areas over the world during the period 1961–2008 (Ray et al, 2012)
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