Stagnation of Wheat Grain Yield Is a Threat to Global Food Security: A Mini-Review with Focus on Winter Wheat Production in France and Germany Under High-Input and Rainfed Farming Conditions

The aim of this mini-review is to provide a short and concise overview on the topic of stagnation of wheat grain yield, with a focus on the European countries France and Germany. These countries are important producers and exporters of bread wheat for human consumption. Thus, both countries are contributing to global food security among other major wheat-exporting nations. Unfortunately, the grain yield of winter wheat has been stagnant for about 30 years in many northwestern European countries under high-input, rainfed farming conditions, including France and Germany. Many different reasons may have contributed to the overall observed yield stagnation at the national level. Potential reasons include, for example, (1) recently changed climatic conditions, (2) altered soil and crop management methods of farmers, (3) economic factors, and (4) agricultural policies, which support environmentally friendly low-input systems which usually have lower yields, such as organic wheat production. Consequently, the reviewed evidence of this mini-review suggests that wheat grain yield stagnation is a multi-factorial phenomenon. There is enough evidence in the literature to say that extreme climatic events such as prolonged heat and drought episodes during wheat growth, and altered management effects of farmers such as the reduced cultivation of legumes in conventional farming systems, are particularly important drivers of the observed wheat grain yield stagnation, but an exact quantification of their magnitude has not been performed yet. Economic and agricultural policy effects are confirmed by a smaller body of evidence and cannot be generalized, for example, due to regional and local differences of wheat production systems. However, it can be said that organic winter wheat production with its usually lower grain yields, is only a minor contributor to the stagnation of average national wheat grain yields in France and Germany, respectively, because the share of organic in the total wheat production area is relatively small (less than 5% of total wheat production area). Because wheat grain yield stagnation is a multi-factorial phenomenon, the abovementioned four categories of important drivers of wheat yield patterns should be considered in order to cope with the wheat grain yield stagnation processes in Europe and elsewhere, because national, regional and local socioeconomic differences in wheat production systems are likely to be considered to maintain sufficiently high wheat grain yields. However, a ceiling of winter wheat grain yield is likely present in many high-yielding wheat production locations in France and Germany, respectively, where it is very difficult to increase wheat grain yield on the existent production area, especially due to increasingly occurring extreme weather events such as heat and drought, which generally counteract yield-improving technologies. Considering the evidence found in the literature, it is quite possible that the stagnation of average national winter wheat grain yields in France and Germany will continue rather than end. Therefore, in France and Germany and possibly elsewhere, enhancing the stability of winter wheat grain yield and quality across years and locations will be increasingly important in the future, presumably, much more important than further increasing the maximum potential yield of winter wheat cultivars. The future overall goal should be to maintain wheat grain yields at least at their current levels. This will be likely possible by implementing various adaptation measures at different scales in future winter wheat production systems. A considerable surplus of wheat grain should also be realized, which can be exported to other countries, in order to be able to continue to contribute to global food security in the future, which will be extremely critical for wheat grain-importing countries with population growth such as Egypt.