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Increasing global food demand will require more food production without further exceeding the planetary boundaries, while at the same time adapting to climate change. We used an ensemble of wheat simulation models, with sink-source improved traits from the highest-yielding wheat genotypes to quantify potential yield gains and associated N requirements. This was explored for current and climate change scenarios across representative sites of major world wheat producing regions. The sink-source traits emerged as climate neutral with 16% yield increase with current N fertilizer applications under both current climate and mid-century climate change scenarios. To achieve the full yield potential, a 52% increase in global average yield under a mid-century RCP8.5 climate scenario, fertilizer use would need to increase fourfold over current use, which would unavoidably lead to higher environmental impacts from wheat production. Our results show the need to improve soil N availability and N use efficiency, along with yield potential.

Episodes of heat stress constrain crop production and will be aggravated in the near future according to short and medium-term climate scenarios. Global increase in cloudiness has also been observed, decreasing the incident solar radiation. This work was aimed to quantify the probability of occurrence of heat stress and cloudiness, alone or combined, during the typical post-flowering period of wheat and canola in the Southern Cone of South America. Extended climate series (last 3-5 decades with daily register) of 33 conventional weather stations from Argentina, Brazil, Chile and Uruguay (23ºS to 40ºS) were analysed considering the period from September to December. Two different daily events of heat stress were determined: i) maximum daily temperature above 30ºC (T>30ºC), and ii) 5ºC above the historical average maximum temperature of that day (T+5ºC). A cloudiness event was defined in our work as incident solar radiation 50% lower than the historical average radiation of that day (R50%). The T>30ºC event increased its probability of occurrence throughout the post-flowering phase, from September to December. By contrast, the risk of T+5ºC event decreased slightly, just like for R50%, and the higher the latitude, the lower the probability of R50%. The T>30ºC plus R50% combined stresses reached greater cumulated probabilities during post-flowering, compared to T+5ºC plus R50%, being 42% vs. 15% in northernmost locations, 26% vs. 19% in central (between 31ºS to 35ºS), and 28% vs. 1% in southernmost locations, respectively. A curvilinear relationship emerged between the monthly probability of combined stresses and the number of days with stress per month. In summary, T>30ºC was the most frequent thermal stress during post-flowering in wheat and canola. Both combined stresses had a noticeable risk of occurrence, but T>30ºC plus R50% was the highest. Evidence of the recent past and current occurrence of heat stress individually, and its combination with cloudiness events during post-flowering of temperate crops, serves as a baseline for future climate scenarios in main cropped areas in the Southern Cone of South America.

Sunflower (Helianthus annuus L.) is an annual oilseed crop primarily grown for its edible oil and fruits in temperate and subtropical climates worldwide. Its oil is somewhat superior to other vegetable oils due to the greater proportion of the unsaturated fatty acids and the content of bioactive compounds (e.g. tocopherols and phytosterols). Here, we update the knowledge about sunflower crop physiology in the context of climate change with focus on (i) the main factors affecting growth and phenology, (ii) the capture and efficiency use of radiation, water and nutrients, iii) how grain number (GN) and grain weight are defined to conform the crop yield and iv) how grain and oil quality are elaborated. All these traits are analysed considering the genetic potential of the crop and how crop management practices can modulate them (by affecting environmental factors).

In the last 40 years, the global use of mineral N fertilizers has increased to support increasing food demand. Misuse of fertilizer has led to environmental problems in some regions and the rarefaction of energy leads to an increasing cost of mineral N fertilizers. For these reasons, improving N-use efficiency of crops and cropping systems is becoming a real challenge to growers, agronomists and breeders. Nitrogen-use efficiency depends on agronomic practices including mineral and organic nitrogen fertilization and the use of legumes in cropping systems, and genetic progress in nitrogen-use efficiency. The objective of this chapter is to develop a framework of the principles governing regulation of N uptake, N allocation and growth of plants and crops, and to apply these principles in tools for improving fertilization management and breeding. A theoretical analysis of the dynamics of plant and crop N demand in relation to growth potential during the crop cycle is developed. Agronomical tools to evaluate nitrogen status of plants and crops are presented and discussed. Physiological and morphological responses of plants and crops to N deficiency are then examined. Finally, the concept of nitrogen-use efficiency is considered in the light of the principles developed previously, and avenues for improving nitrogen-use efficiency through plant breeding and agronomy are discussed from a crop physiology point of view.

This chapter considers the genetic basis of yield potential and the implications for breeding, identifies barriers to future gains in yield potential, and assesses the scope for the use of physiological tools to select for high yield potential. Yield potential is the yield of cultivars when grown in environments to which they are adapted with nutrients and water nonlimiting and with pests, diseases, weeds, and other stresses effectively controlled. It is somewhat theoretical since “optimal” radiation and temperatures, for example, most likely interact with genotype and growth stage. This differs from the attainable yield, which corresponds to the best yield achieved through skillful use of the best available technology. On-farm yields normally realize from 60 to 80% of attainable yield; the gap relates to the physical environment being suboptimal on most farms and to moderate use of fertilizer and crop protection measures in environmentally sensitive farming. The yield gap may therefore be quite large, especially in the more marginal environments.