Agricultural sciences in transition from 1800 to 2020: Exploring knowledge and creating impact

Europ. J. Agronomy 59 (2014) 96–106

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European Journal of Agronomy journal homepage: www.elsevier.com/locate/eja

Agricultural sciences in transition from 1800 to 2020: Exploring knowledge and creating impact Huub Spiertz ∗,1 Centre for Crop Systems Analysis (CSA), Plant Sciences Group, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands

a r t i c l e

i n f o

Article history: Received 27 January 2014 Received in revised form 22 May 2014 Accepted 3 June 2014 Keywords: Agronomy Crop physiology Plant breeding Climate change Cropping system Resource use Technology Innovation

a b s t r a c t Transitions in agricultural sciences are brought about by incorporating new findings and insights emerging from biological, chemical and biophysical sciences, by more advanced ways of experimentation and last but not least by quantitative methods and models for data analyses and processing. Major breakthroughs occurred from 1800 onwards when new insights on photosynthesis and mineral nutrition were incorporated in the theory on the growth of crops. It took almost half a century before the humus theory was replaced by a more sound theory on mineral nutrition. The publication by Darwin on domestication in 1868 and the rediscovery of Mendel’s laws in 1900 gave a boost to genetics underlying classical plant and animal breeding, which was mainly based on crossing and selection. A major accomplishment of the evolutionary synthesis was the compatibility of Mendelian inheritance with Darwinian natural selection. The discovery of the DNA-structure in the mid-fifties of the 20th century on modern plant breeding showed already impact within some decades. To assess the wide diversity of plant traits for the performance of plants in yield and quality of the produce advanced phenotyping method under controlled conditions has become popular. Genome-wide selection for environments with multiple stresses, however, does require phenotyping in situ. Since 1800 the transition from observations on the plant, field and farm towards dedicated experimentation took place. During the 19th and 20th century the methods for experimentation and data analyses were strongly improved. It took until the mid-20th century before the importance of experiments under controlled conditions was recognized. Studies of plant processes under controlled conditions provided the building blocks for mechanistic modelling of crop growth and production. A systems approach combining knowledge at different scales and incorporating cutting-edge findings from the basic sciences into applied sciences will become important for making a great leap forward in developing agricultural science with impact. Transitions in agricultural research will continue to depend on progress made in the related basic sciences and the capacity for agricultural research and innovation. Therefore, an adequate public funding is required to maintain or even accelerate progress in sciences. This requires the support of the public at large. Public–private partnerships will be needed to bridge the gap between science and innovation. © 2014 Elsevier B.V. All rights reserved.

Contents 1. 2. 3.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 Agricultural sciences in the 19th century: exploration and invention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 Agricultural sciences in the 20th century: capacity building in the public and private domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 3.1. Genetics and plant breeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 3.2. Research on photosynthesis and assimilate allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 3.3. Research on the use of water and nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 3.4. Research on modelling crop growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

∗ Tel.: ++31 317 485 315. E-mail addresses: [email protected], huub [email protected] 1 Emeritus-professor Crop Ecology. http://dx.doi.org/10.1016/j.eja.2014.06.001 1161-0301/© 2014 Elsevier B.V. All rights reserved.

H. Spiertz / Europ. J. Agronomy 59 (2014) 96–106

4.

5.

Agricultural sciences in the 21st century: challenges and opportunities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. Research on closing yield gaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. Research on the genetics of yield improvement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3. Research on adaptation to abiotic stress and climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4. Research on mechanistic and functional–structural plant modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5. Research on ecological intensification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Discussion and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix A. Science and society: the role of leading scientists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction Agricultural science developed in the Arab, Asian, Greek, Maya and Roman cultures based on empirical insight and the wisdom of people (e.g. Cato, 234–149 BC. “De AgriCultura”). Famous are the intricate irrigation systems of at least 2000 years ago. Without written documents and oral communication agricultural methods, tools and infrastructure would not have been developed. The evolution from primitive to modern farming systems in Europe was described by various authors (Zadoks, 2013). Mediaeval Europe (11–14th century) shifted from the subsistence agrarian economy to one where spatially dispersed trade in agricultural commodities could support societies that devoted resources to develop monastic institutions and cultural works in cities (Fraser, 2001). The relationships between agricultural revolutions and socio-economic developments during the period from 1450 to 2010 were studied by Moore (2010). He concluded that capitalist agencies pioneered successive agricultural revolutions, resulting in food surpluses. However, around 1800 a family of the working class in Berlin spent about 73% of their household budget on food of which two-thirds on bread (Braudel, 1979). Thus, during periods of political turmoil there was always a looming food crisis. With the growth of cities more food than the subsistence level of the farming community had to be produced. Progress in agricultural research took place much later than the modernization of sciences in general. A giant in the modernization of science has been Isaac Newton with his publication of the Philosphiae Naturalis Principia Mathematica in 1687 (Janiak, 2012). He was the first scientist to develop new concepts on space and time. Newton stressed the importance of theory and experiment. It took until about 1800 before systematic experimentation was introduced in agricultural sciences. The development of agricultural sciences has been shaped by societal needs and demands on the one hand and by knowledge provided by basic sciences. Some trends in society and science are presented in Table 1. In this review major events affecting the content and course of agriculture science during the period from 1800 to 2000 are presented and discussed. The hypothesis is that major transitions in agricultural science were built on new insights in basic sciences. This applies especially for chemistry, physics, biology and mathematics. Chemistry played an essential role in the development of new theories on plant nutrition (Van der Ploeg et al., 1999), chemical regulation of growth (Davis and Curry, 1991), inventing the DNA structure (Watson and Crick, 1953), and a better understanding of food quality and safety (Friedman and Mc Donald, 1997). The role of physics has been essential in developing theories on photosynthesis (Farquhar et al., 2001), crop geometry and light use (Leuning et al., 1995), and on soil structure and processes (Jury et al., 2011). The role of biology in developing new insights on crop phenology, pest and disease incidence, and more recently the applications of molecular and cell biology in plant breeding (Stamp and Visser, 2012). Last but not least mathematics played a role in the development of statistical analyses and mechanistic modelling (De Wit, 1968). The objective of this review is to evaluate the boundaries and characteristics of major breakthroughs in agricultural sciences

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100 101 101 102 102 102 103 103 103 104

in the past (19th and 20th century) and present (21th century). Furthermore, an outlook is presented on future developments in agricultural sciences based on the present developments. 2. Agricultural sciences in the 19th century: exploration and invention In the 17th century various theories existed already on how plants were fed by the soil. The role of water and manure was already known for centuries. However, a variety of theories existed on the uptake of salts, ‘juices’ and even soil particles by plants. The pioneer studies by Priestly in 1777 and Ingen-Houszin 1780 on leaf photosynthesis laid the basis for understanding the role of carbon dioxide assimilation by plants. These new insights were published in a book “Recherches chimiques sur la vegetation” (De Saussure, 1804). New findings were conflicting with the dominant theory at that time – the “Humus Theory”, strongly defended by Albrecht Daniel Thaer among others at the beginning of the 19th century. The German agronomist Thaer became well-known through his books in which he published results of large scale field experiments carried out in a systematic way to underpin the conceptual framework of “rational agriculture” (Feller et al., 2003). He developed a scale to rate the production function of soils taking into account cropping system and nutrient requirements of crops. The production value ranged from 1514 to 5942 units for farming systems varying from purely arable (triennial rotation including fallow) to mixed farming including pasture. The most productive system turned out to be based on keeping cattle in the stable to maximize recycling of nutrients by manure applications on arable land. Thus, he choose already an integrated approach on the sustainable use of nutrients by considering recycling as an integral part of mixed farming: combining land use, arable cropping and cattle farming (Thaer, 1809). The “Mineral Theory” was developed by Sprengel and later widely published by Liebig during the 19th century (Van der Ploeg et al., 1999). It was clearly demonstrated that plant nutrients were taken up by the plant as mineral components. The new theory did boost the experimental work on nutrient uptake by crop plants. Most well-known is the initiative of Gilbert and Lawes in 1843 to start large long-term field experiments at Rothamsted (UK) to study the effects of the use of fertilizers and manure on soil fertility, biomass production and crop yield (Jenkinson, 1991; Rasmussen et al., 1998). The research on the famous Broadbalk fields contributed strongly to the understanding of the effect of management (manuring, fertilization, rotation, weed, pest and disease control, etc.) on the response of crops to nutrients. From the theoretical perspective the Law on Diminishing Returns and the Law on the Limiting Factor (Liebscher, 1895; De Wit, 1992) contributed to the understanding how to manage fertilizer input. 3. Agricultural sciences in the 20th century: capacity building in the public and private domain Synergy between agricultural and plant sciences is a characteristic of progress made in the 20th century. The growing

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understanding of the functioning of individual plant and of plant communities, especially in sole crops, but also in different cropping arrangements (mixed crops, intercrops, relay-intercropping, double cropping, etc.) has been a driving force for research and innovation on crop productivity. Field experimentation became more scientifically reliable and efficient by the important contributions of Fisher and colleagues to the theory and application of agricultural statistics (Street, 1990). It took until the mid-20th century before the importance of experiments under controlled conditions was recognized (Evans et al., 1985). Studies of plant processes under controlled conditions provided the building blocks for mechanistic modelling of crop growth and production. Landgrant colleges in the US, state institutes in France and the UK, university faculties in Germany, Italy and other European countries carried out experimental research in the field of agronomy and breeding (Spiertz and Kropff, 2011). As a consequence, progress was made in breeding (semi-dwarf cultivars), agronomy (use of nitrogen, herbicides, fungicides, etc.) and technology (advanced equipment for soil tillage, sowing, spraying and harvesting). During the second half of the last century not only yields per ha increased with a factor 10, but labour productivity (grain yield per hour) even more by a factor of 200 (De Wit et al., 1987). Higher productivity of agriculture depended greatly on innovation in farming practices. A revolutionary change in cereal production, the solid base of global food security, was made when large-scale investments were made in agricultural research, land reclamation and supporting infrastructure (e.g. irrigation systems) by national governments and the World Bank as well as foundations such as the Ford and Rockefeller Foundations (Zeigler and Mohanty, 2010). The need not just to improve crop productivity, but to develop integrated systems for food, feed and bio-based feed stocks that are sustainable became an incentive for building bridges between the various domains of sciences: agronomy, biology, breeding, (bio-)technology, nutrition and health, and social sciences (Wezel et al., 2009; Spiertz and Kropff, 2011; Albajes et al., 2013; Léo and Pintureau, 2013). The underpinning of the

above-mentioned general progress in agricultural research is presented for four key areas: genetics and plant breeding, photosynthesis and assimilate allocation, use of water and nutrients and modelling crop growth. 3.1. Genetics and plant breeding A major breakthrough in genetics in the 20th century were the rediscovery of the Mendel Laws in 1900 by Hugo de Vries and Erich von Tsermak-Szeneygg (Allen, 2003; Brown, 2013). Half a century later, in 1953, the Watson–Crick model on the structure of DNA was presented, which provided the basis of molecular genetics and later allowed application of knowledge on genetic information of traits. The impact of this invention for molecular genetics became clear quite soon after restriction enzymes and cloning were implemented. The first transgenic commercial product was human insulin, approved in 1982. The very beginning of genetic modification of plants was the cutting edge research of Marc van Montagu (1933–) and Jeff Schell (1935–2003) at Ghent University on the discovery of the Ti plasmid and using Agrobacterium to transfer genes to plants. Van Montagu had foreseen a bright future for this new tool and therefore founded in 1982 a company Plant Genetics Systems in Ghent, Belgium (Van Montagu, 2011). The Agrobacterium-mediated plant gene engineering laid the cornerstone for the breeding of Bt Cotton in Asia and Bt Maize in Europe and the US. The pioneering work on Arabidopsis thaliana started in the beginning of this century by Friedrich Laibach in Germany. In the US, the group of Chris Somerville used mutants in physiological research and in the Netherlands screening mutants for specific physiological traits was started (Koornneef and Meinke, 2010). Ultimately, this research effort led to the choice to use Arabidopsis as the model plant for research in plant biology (Meinke et al., 1998). In 2000, Arabidopsis was the first plant species of which the genome sequence could be published. Arabidopsis research has led to the discovery of many gene functions up to the molecular and biochemical levels, which was often found to be translatable

Table 1 Trends in social issues, natural sciences and agricultural sciences in the period from 1800 to 2000. Period

Social issues

Natural sciences

Agri-sciences

19th century

Food insecurity Low agricultural productivity

Humus theory (Thaer) Mineral nutrition theory (Sprengel/Liebig)

20th century

Industrialization Population growth (from 2 to 6 billion) World war I and II (destruction and starvation) Agricultural intensification (“Green Revolution”) Environmental concerns (Silent Spring, Rachel Carson): a. Biodiversity b. Climate change c. Water quality d. GHG-emissions Sustainability paradigm IT, communication and innovation

Plant physiology (photosynthesis and sink-source theory) Genetics (Mendel Laws) Chemistry: a. Chemical nitrogen fixation b. Development of biocides (pesticides, etc.) c. DNA-helix structure (Watson & Crick) Genetics: a. Bt-transformation b. Plant ideotype c. Rht-1 dwarfing gene d. Arabidopsis plant genome Plant and crop sciences: a. Photosynthesis and transpiration of leaves b. Mechanistic crop modelling Nanotechnology

21th century

Population growth, migration and urbanization Ageing population and health concerns (food-related diseases; obesities, etc.) Scarcity of resources (energy, land, water, phosphorus, metals, etc.) Weather extremes: a. Heat and drought b. Tsunamis, tornados and flooding Organic-based food production/abolishing chemical biocides in food production

Molecular genetics and synthetic biology Stem cell functioning Synthetic biology

Tripod model: Education–research–extension Strengthening of the research infrastructure by Government and Industry to support: a. Research on improving productivity of land and crops b. Research on mechanization and substitution of human labour c. Research on lowering environmental impact and developing more resource-efficient cropping and farming systems d. Precision farming by fine-tuning of dosing and timing of external inputs (energy, nutrients, water, herbicides, fungicides, pesticides) Transition of agricultural into general science-based universities Food and nutrition era: a. Top Institutes Food and Nutrition (TIFN) b. Joint research efforts by the public and private sectors Closing yield gaps: a. Molecular-assisted plant breeding b. Advanced decision support systems for crop and farm management Embedding ecological principles into agronomy

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to crop species. Recent technological developments such as next generation sequencing made research approaches that previously were only possible in Arabidopsis now also amenable to crops and led to an increasing knowledge on where plant species differ in the biochemical mechanisms underlying traits and trait variation (Koornneef, pers. comm.). A great leap forward in plant breeding was the introduction of hybrid varieties in maize since 1916 and the introduction of disease resistance genes in cereals, potato and vegetables since the mid-1950s and dwarfing genes in wheat and rice since 1965 (Fischer and Edmeades, 2010). The development of double and single hybrids was mainly undertaken by the private sector in the US (Duvick, 2005), whereas, the lead in introducing semi-dwarfs of wheat and rice was taken by CIMMYT (Reeves and Cassaday, 2002) and IRRI (Khush, 2013). Also public sector breeding institutes in West Europe, especially PBI in the UK, were successful in breeding high-yielding modern varieties. Classical plant breeding of wheat and other cereals became an important activity in agricultural universities since the beginning of the 20th century. In the UK various institutes were established: John Innes in 1910, Plant Breeding Institute in 1912, Scottish Plant Breeding Station in 1921 and Welsh Plant Breeding Station in 1919. Despite the big successes in breeding and releasing new varieties of wheat and barley, the ARFC Plant Breeding Institute (PBI) was privatized as part of a policy to reduce public spending on agricultural research in the 1980s (Thirtle et al., 1998). In The Netherlands already around 1930 plant phenological and physiological research was initiated to support plant breeding with a better understanding of the functioning of crops. Feekes did pioneering research on day-length sensitivity of wheat genotypes and developed a morphological scale to score development rate (Zadoks et al., 1974). Traditionally, leafy and tall crops have shown to be more competitive to weeds. Since the full control of weeds by mechanical methods and/or chemical control, breeding for shorter less leafy crops in cereals turned out to result in higher yields (Sinclair, 1998). This breeding strategy resulted in allocating more carbohydrates in the reproductive organs (grains) or the harvestable vegetative parts (e.g., roots of sugar beets). An innovative concept was developed by Donald in Australia on the plant ideotype of wheat (Donald, 1968; Donald and Hamblin, 1976). Such a plant ideotype would combine specific traits favourable for photosynthesis, assimilate allocation and grain yield. It was hypothesized that tillering should be restricted and erect leaves were needed to raise the reproductive capacity of wheat. An erect leaf angle was considered to improve light capture and utilization by crops and less tillers would favour the carbon allocation to grains. The cooperation between plant breeders and crop scientists based on the concept of plant ideotype was not always successful. Concepts and methods were sometimes too different among disciplines to facilitate an easy exchange of ideas and insights. The concepts of Donald were not implemented in breeding, because many other traits turned out to be more strongly associated with yield (Reynolds et al., 2012). The strength and weaknesses of ideotype breeding to increase rice yield potential are clearly presented by Peng et al. (2008). They concluded: “The success of super hybrid rice breeding in China and progress in NPT breeding at IRRI suggest that the ideotype approach is effective for breaking the yield ceiling of an irrigated rice crop”. IRRI started breeding on the New Plant Type (NPT) of rice in 1989. The choice of extreme plant traits, e.g. 200–250 grains per panicle, led to poor grain filling. China established in 1996 a mega project on the development of “super” rice. The inter-subspecific rice cultivar Liangyoupeijiu was released in Jiangsu Province in 1999. This super rice cultivar yielded 28.6% more than the check cultivar Shanyou 63 in a first experiment. Since, extensive research has been carried out on morphological and physiological traits that then may contribute to this success. Based on the new insights Prof Longpin Yuan

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started in 1998 a super “hybrid” rice breeding programme with a very specific morphological description of the ideotype (Yin et al., 2003). This approach turned out to be very successful. Nowadays, genetic modified crops cover 12% of the arable land globally; in the EU-countries this acreage is not more than 1%. The polemic on genetic modified organism in Europe is not based on scientific evidence, but largely by an ethical and/or emotional response to a new technology. This response is fuelled by NGOs like Green Peace in their fight against the economic power of multinationals (Federoff, 2013). The case of the ‘golden’ rice, where genes derived from maize and bacteria are used to enrich the beta-carotene content of rice shows that concerns by the public on genetic modification were abused by Green peace and related green organizations (Christou, 2013; Potrykus, 2013). The beneficial effects on the health of people in poor countries (e.g. Bangladesh, India and Philippines) with a deficiency in vitamin A could not convince policymakers and protesters. It shows that the mistrust in GMO-technology as such is deeply rooted in most of the EU-countries (Ammann, 2014). Any technology can be used in a bad or good way; therefore, not the technology, but how and for what purpose the technology is used should be critically assessed. Nowadays, a lot of information is needed for registration and permission; for GMO-crops much more details have to be provided than for crops conventionally bred. To overcome this mistrust the involvement of public research organizations and more transparency to the public in the utilization of modern technologies will be necessary (Mayer and Stirling, 2001). The complicated and expensive regulation for GMO-crops is also a hurdle for vegetable and small crop breeders to use this technology. 3.2. Research on photosynthesis and assimilate allocation After the pioneering work of Ingen-Housz and others around 1780 not much progress was made on measuring photosynthesis of plant leaves for 150 years. In the mid-1950s methods were developed to measure the rates of leaf photosynthesis and transpiration simultaneously (Gaastra, 1959). These gas exchange methods were later refined (Von Caemmerer and Farquhar, 1981), and further incorporated with other measuring techniques and now become a routine measurement for studying leaf photosynthesis (Long and Bernacchi, 2003). Crop and leaf enclosures were also used to measure plant responses to environmental factors, and to study the functioning of new systemic herbicides (Van Oorschot and van Leeuwen, 1988). To bridge the gap between the functioning of single leaves and a crop, researchers developed mobile equipment’s that made it possible to measure the rates of photosynthesis and transpiration in crop enclosures at multiple locations (Leach, 1979). The next development was to study effects of elevated CO2 on crop photosynthesis and crop growth on open-top chambers, so-called OTCs (Schapendonk et al., 2000) or on Free-Air CO2 Enrichment (FACE) under field conditions (Kimball et al., 1995). FACE experiments are also suggested as a platform to conduct screening of genotypes and to elucidate the inheritance and mechanism that underlie genotypic differences in productivity under elevated CO2 (Ainsworth et al., 2008). A much simpler approach to assess yield was developed by Monteith and co-workers. They hypothesized that biomass production and therefore also grain yield was mainly related to the amount of intercepted light (Goudriaan and Monteith, 1990). The assumption is that light-use efficiency (LUE) does not differ greatly among treatments for a given crop in a temperate climate. The importance of light interception over light-use efficiency was also found for intercropping systems (Zhang et al., 2008), such as the relay strip intercropping of wheat and cotton. However, it was also shown that for the yield determining carbon accumulation in reproductive organs stay-green characteristics associated with a higher LUE can make a difference (Dreccer et al., 2000). These new insights should

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also be used to improve the photosynthesis modules of crop growth models. The first findings of a functional relationship in plants between above- and below-ground parts were presented by Brouwer (1983). The allocation of carbohydrates and nitrogen during the reproductive period in wheat in relation to light intensity and temperature was studied by Spiertz (1978) in controlled environments. He found that there exists a functional relationship between the amount of assimilates stored in grains (sink) and the availability of carbohydrates and proteins by current assimilation and/or remobilization of reserves from the vegetative parts. This relationship is affected by climatic conditions and nitrogen supply. Research on the carbohydrate and nitrogen economy of cereals has been continued for decades and got a boost when the determinants of genetic variation in nitrogen accumulation, partitioning and remobilization in wheat and rice could be assessed (Gaju et al., 2014; Khush, 2013). 3.3. Research on the use of water and nutrients Drought is the main abiotic constraint for crop growth and yield under semi-arid and water-limited temperate conditions for most crops. Generally, C4 crops need less water than C3 crops to produce the same amount of dry matter (Lawlor and Mitchell, 1991; Alberto et al., 2013). In rainfed environments water availability is a major source of variability in crop yields. Under drought conditions the annual increase of yields of cereals during the second half of the 20th century was much lower than under optimal water supply. The gap between the best varieties under the two conditions increased from one to about five tonnes per ha in 1960 and 2000, respectively (Araus et al., 2002). Therefore, much attention has been paid to affect evaporation and transpiration by soil and crop management. The ratio between yield and evapotranspiration (ET), the so-called water use efficiency (WUE) has been widely used as the parameter to determine the productivity of crops under water-limiting conditions (Fischer and Turner, 1978). To get more insight in the opportunities to improve WUE by agronomic measures Asseng et al. (2001) used the Agricultural Production Systems Simulator (APSIM) to upscale experimentally derived parameters in time and space to the farming system level. The growing availability of fertilizer N at low costs after World War II gave a push to research on dosing and timing of nitrogen in major cropping systems (rice, wheat and maize). Under rainfed as well as irrigated conditions water availability determines also the response of the crop to N applications. The potential for water saving in flooded rice systems has been extensively explored (Bouman and Tuong, 2001; Belder et al., 2004). Water savings in rice ranged from 5 to 40% without much impact on the yield level. Thus, improved water management based on a quantitative understanding of evapotranspiration and unnecessary evaporative and seepage losses, did result in a great leap forward in water saving and in water-use efficiency and water productivity. In supplementary irrigated cropping systems matching demand and supply of nutrients was realized by fertigation (Castellanos et al., 2013), while in high-yielding winter wheat crops the timing and dosing of nitrogen applications was based on crop demand during specific growth phases (Spiertz, 2010). Improved efficiency of nutrient use at a field and farm scale, both aiming at increasing crop yield and reducing losses, is dependent upon the magnitude of matching nutrient supply and demand of the crop (Cassman et al., 2002). Water availability strongly affects N-uptake and -recovery in rice (Belder et al., 2004). For high yielding corn with controlled irrigation regimes and a mean grain yield of 14.7 Mg ha−1 , mean fertilizer N recovery (ANR) in the aboveground biomass was reported to be 74% at the lowest N rate compared with 40% at the highest N rate (Wortmann et al., 2011). For high-yielding temperate wheat crops ANR can be as high as 0.80 (Spiertz and De Vos, 1983). Thus, the apparent nitrogen recovery of the main food

crops is strongly associated with agroclimatic conditions, water regime and N supply during the growing season. The agronomic nitrogen use efficiency, derived from apparent recovery (ANR) and physiological nitrogen use efficiency (PNUE), amounts to 0.50 on average for crops under temperate conditions. 3.4. Research on modelling crop growth The quantitative understanding of these plant physiological processes at the crop level became the core of the theoretical framework for mechanistic crop modelling (De Wit, 1968). The first estimate of a 10 tonne potential yield for wheat under optimal water and nutrient supply was mainly based on photosynthesis processes and a conventional harvest-index of 0.40. The dramatic increase in harvest-indices during the 1970s by introducing semi-dwarf wheat cultivars was not foreseen. The theory of quantitative analysis of inter-specific plant competition was developed in the early 1960s. This methodology was instrumental to study the competition between crops and weeds. An eco-physiological model to study competition under different weather conditions was developed by Kropff and Spitters (1992). An overview of model development and applications in the first 25 years of mechanistic crop modelling are presented by Bouman et al. (1996). Progress has also been made in modelling crop growth and yield of horticultural crops (Marcelis et al., 1998). Since, the pioneering phase crop models became widely used in studies on cropping and farming systems, improving crop water and nutrient use, reducing environmental emissions and climate change (Jeuffroy et al., 2012). 4. Agricultural sciences in the 21st century: challenges and opportunities Worldwide there is an increasing awareness that more investments in agricultural research are needed to solve the needs of a fast growing global population while the essential resources to produce food, feed and green feed stocks become more scarce (Lambin and Meyfroidt, 2011; Serageldin, 1999). This is especially the case for land, water and some essential nutrients (e.g. phosphorus and zinc). The challenge will be to produce more with less inputs. During the last century agronomist and ecologist had conflicting goals, such as intensification of agricultural production and nature conservation (Robinson and Sutherland, 2002). Priorities in agricultural research moved from environmental topics, such as emissions of nutrients, to combing food security, food safety and quality of life. The latter integrates health and well-being of people with concerns on longterm effects of climate change and biodiversity loss. In the future concerted actions by researchers with a background in contrasting disciplines are needed to make progress in achieving food security and improving the quality of life for all people (Yu et al., 2012). Sensor and information technology will contribute to make crop production more resource efficient (Zhang et al., 2000). The productivity per unit of external input has to be increased substantially in the coming decades in order to meet the growing demand and environmental boundaries such as emissions to soil, water and air. The development in agricultural research at present and in the future will not only be determined by the growing demand for food and feed, but also the demand for feed stocks in the emerging biobased economy (Van Dam et al., 2005; Spiertz, 2013; Zilberman et al., 2013). These feed stocks will be needed in a circular economy that promotes the re-use of material and minimizes the use of material derived from fossil fuels. In a low carbon economy, biobased fuels are going to play a more important role. Research capacities have been strengthened to study the potential of 2nd generation plant-based resources, but also the potential of algae and cyanobacteria (Melis, 2009; Wijffels and Barbosa, 2010). However,

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progress can also be made in crop plants (Zhu et al., 2010a,b). The impact of the research on fundamental physiological processes for crop yields will become not clear at the short term. Nevertheless much progress has been made in various fields. These are discussed for the following topics: closing yield gaps, genetics and yield improvement, adaptation and climate change, modelling and ecological intensification 4.1. Research on closing yield gaps Major contributions to achieve higher and more stable yields in small cereals, especially wheat and rice, were achieved by technology transitions based on the introduction of dwarfing genes, chemical weed and pest control and optimizing water and nitrogen supply. The vast on-going activities on quantifying yield gaps for a range of cropping systems and agroecological environments resulted from a study by Lobell et al. (2009) on the importance, magnitude and causes of crop yield gaps. They found that in most irrigated crops (wheat, rice and maize) yields appear to centre around 80% of the yield potential; however, for rainfed systems yields stagnated at about 50% of the potential yield. They concluded that under rainfed conditions there is ample room for improvement. The research on yield gaps has grown to maturity by improving the problem definition and research methods. Van Ittersum et al. (2013) suggested that “yield gap analyses with local to global relevance are needed to inform decisions on policy, research, development and investment affecting future crop yield and land use”. This objective may be too ambitious taking into account that progress made by breeding and the role of the economics and global trade are not taken into account. A more science-based analysis of yield gaps for major cropping systems at different scales is currently carried out. It will result in a Global Yield Gap Atlas that may give guidance to future research and development to narrow the yield gap. Depending on agro-ecological and soil conditions it will result in more external inputs: water, nutrients and crop protection measures. 4.2. Research on the genetics of yield improvement Concerns on progress in genetic improvement of cereal yields under optimal conditions (Yp) and water-limited conditions (Yw) are expressed by Hall and Richards (2013). They conclude that the current and expected future rates in yield progress of maize, wheat and rice lag behind the annual increase (ca. 1.5%) needed to meet the projected demands for cereals in 2050. As potential areas to make progress on the long run they identified the improvement of the photosynthetic capacity for both non-stressed and waterlimited conditions, and the improvement of root systems to capture more water in dry environments (see also Reynolds and Trethowan, 2007). Raising productivity through increasing crop photosynthesis was proposed by various researchers (Long et al., 2006; Parry et al., 2011; Gu et al., 2014). They proposed options for increasing photosynthetic capacity and efficiency of C3 crops, such as ‘better’ Rubisco, and improving efficiency of light capture. Another approach is to engineer the C4 photosynthetic pathway into C3 crops, which got recently much attention in rice research (Hibberd et al., 2008). This type of research in rice was identified by Zhu et al. (2010) as: “An ideal arena for systems biology research”. However, proof of concept for this great leap forward in photosynthesis of a major food crop is needed. Changes in agricultural practices (e.g. less diversity in crop species and varieties) and in the regulation of the use of pesticides are increasing the demand for durable resistances to pests and diseases (Summers and Brown, 2013). Concerns are the small number of crops and the low rates of breeding progress in self-pollinating cereals. There are contrasting views on making progress by

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breeding. Stamp and Visser (2012) believe that progress can be made by implementing new technologies and genomics as well as by traditional plant breeding. Trade-offs between new genes for resistance and genes for improving productive were found by Summers and Brown (2013). It will be a big challenge for plant breeders to provide excellent germplasm and varieties for a sustainable increase of plant production meeting the demands of society by 2050 (Seifi et al., 2013). In the past the time-scale from initial research to the release of new cultivars to farmers was around 20 years. The time taken to the identification and incorporation of new traits by conventional breeding is very slow. When appropriate germplasm is available then breeders need fast and effective selection methods such as molecular markers and advanced phenotyping (Richards et al., 2010). The broad potential of recombinant DNA technology and metabolomics has been shown in animal as well as plant breeding (Miflin, 2000; Putri et al., 2013). Nowadays, metabolomics is a key technology for plant improvement facilitating phenotyping the chemical composition of plants. This information is useful to improve quality, disease and stress tolerance. Modern analyses offers the potential of molecular analysis of the genes contributing to the performance of plants and animals at decreasing costs and provides tools to improve productivity and associated traits. A gain of three years in developing drought resistant rice varieties by using genomics-based precision breeding was shown by Swamy and Kumar (2013). The projection of a technological revolution in the tools to acquire knowledge about the genetics of crop plants by Miflin (2000) has become true. The capacity to sequence DNA increased dramatically during the first decade of the 21st century and as a consequence the costs per genome decreased. Much emphasis and research capacity has been devoted to identify the sequence of specific genes; this was coined the genocentric view. Miflin (2000) made a warning that the pace of determining DNA-sequences should be a in balance with the capacity to determine the function of the genes used for crop improvement. More emphasis on phenomics is needed to balance the genocentric view by a phenocentric approach. Tardieu and Tuberosa (2010) stressed the importance of using phenotyping systems and platforms. Genomic selection will become the most advanced breeding tool to accelerate breeding. An example of a recent breakthrough in raising yields of rice is the discovery of a unique gene – SPIKE – in an Indonesian landrace (Fujita et al., 2013). When this gene is present in a near-isogenic line of the indica cultivar IR 64 it increases spikelet number, leaf size, root capacity, and the number of vascular bundles, resulting in a yield increase of 13–36% under optimal conditions. Since the beginning of the breeding programme for New Plant Type (NPT) at IRRI in 1989, the SPIKE-gene is the first breakthrough in the yield potential of rice. It should be noted that these claims on increasing yield potential should be validated in field experiments under contrasting conditions as well as by crop modelling. Especially, the performance under conditions where inputs are limiting due to high costs or lack of availability should play a role in selecting adapted varieties. Genetic modified crops, such as soybean, maize, cotton and canola, were introduced in the late 1990s in the USA and next in many countries globally, except for the EU-countries. The adoption of GM maize and soybean in the USA has been very fast: in a time-span from 1996 to 2010 from almost zero to more than 90% (Xu et al., 2013). The driving force for this adoption is only partly yield increase, but mainly a more cost-effective control of weeds and pests. In soybean cultivation it is often combined with conservation management of the soil (zero or minimum tillage). The on-going debate on the acceptance and safety of GM-crops is dominated by ethical, religious and social views, especially in the European Union. To facilitate the discussion among educated citizens, consumers and scientists about the use of modern breeding tools, we should clearly distinguish between genetic modification and molecular based tools in conventional

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breeding. The importance of growing crops with zero tillage (soybean), insect resistance (Bt-cotton) and improved drought tolerance (maize) by genetic modification is clearly shown by the vast expansion of various GM-crops in many countries. The pressure on research institutes to show benefits of the vast research spending on genomics should be counterbalanced by checks and balances in the agricultural research community. The use of molecular based breeding techniques is mainly opposed by people that adopt the philosophy underpinning organic farming. The concerns of all consumers have to be taken serious. However, at the same time some researchers (Jacobsen et al., 2013) contribute to more confusion by considering all molecular-based breeding methods as genetic modification. They state that the need for GM-crops to feed the world does have no scientific support, but that it reflects only corporate interests. Without presenting any scientific evidence, they claim that agricultural biodiversity is threatened by genetic modification of crops (Federoff, 2013). In their paper they confused also future challenges in feeding the world and the need for a more balanced research funding. Spiertz (2013) made already earlier a plea for more public funding of research on so-called minor crops. The urgency of diversification in growing a wider range of food crops for food security and human health is underpinned by a study of Khoury et al. (2014). They conclude that narrowing the diversity in crop species results in national food supplies that became more similar in composition because of the increased supply of globally available cereal and oil crops.

4.3. Research on adaptation to abiotic stress and climate change Crop responses to climatic variation were evaluated by Porter and Semenov (2005). They found that climate variability and the frequency of extreme events are important for yield and its stability. They made a plea that modellers of climate change should make more use of the knowledge on crop critical temperatures and their temporal resolution. Based on an analysis of physiological determinants of yield responses to drought Araus et al. (2002) made a wide array of recommendations to breed cereals for mild to moderate drought conditions. They stated that “analysing physiological determinants of yield responses to water may help in breeding for higher yield and stability under drought conditions”. Besides avoidance and tolerance traits most yield gain can be achieved by improvements of traits associated with water use, water-use efficiency and assimilate relocation (harvest-index). To identify “vulnerability hotspots”, where cereal production may decline in response to future climate change and drought a study was carried out by Fraser et al. (2013) in which they integrated the results of socio-economic and hydrological modelling. In their analysis of the adaptive capacity of cropping systems, they found a significant risk on drought effects on wheat yields in many parts of the world; especially: western Russia, northern India, and south-eastern South America and Africa. This is a different type of exploring crop responses to climate change than carried out with mechanistic crop growth models. Results may be flawed by the fact that the physiological adaptation of cereal crops to temperature is not taken into account. Options for intensification of maize production on degraded soils in Zimbabwe were shown by Rusinamhodzi et al. (2013). Not only aboveground crop responses do matter, also the belowground processes that determine crop response to abiotic stress are important. In a study by Smithwick et al. (2012) on tree responses to changes in the belowground biogeochemical environment, it is shown that high nitrogen depositions do affect root lifespan, rooting depth and/or mycorrhizal colonization. Belowground interactions are also found in intercropping of various crop species, especially cereals and legumes (Zhang et al., 2010). The degree of facilitation and competition in nutrient acquisition and uptake does determine crop performance. At a low

P status of soils facilitation can contribute to a better availability of this limiting nutrient. 4.4. Research on mechanistic and functional–structural plant modelling An example of basic knowledge provided by plant sciences is the finding that among Arabidopsis natural variants all dwarfs are mutations in the same gene as the semi-dwarf genes of rice and barley (Barboza et al., 2013). Thus looking at natural variation one may predict which genes are useful in plant breeding too. A more advanced understanding of the control of plant morphogenesis requires a better insight in the genes involved in transcriptional control. The use of the Arabidopsis embryo to study embryogenesis in space and time was reviewed by Wendrich and Weijers (2013). The goal is to develop models that use existing knowledge, but also to identify emerging traits that are important but not yet known. This is a kind of pathway modelling at much lower aggregation levels than the above-mentioned crop modelling. This type of research is still in an early phase and therefore it will difficult to identify yet potential applications. A better understanding of the morphogenesis of plant organs (sink or source) may guide molecular-assisted plant breeding to improve plant traits. At the lower organizational level, there are quite some examples that modelling based on auxin transport predicts quite well meristem formation, flower and root development (Scheres and Xu, 2006). However, for traits such as flowering time (‘earliness’) the up-scaling from gene to crop phenology is less complex (Laurie, 1997). The transfer of sugar beet from a summer to a winter annual is an example of increasing yield by only modifying one or a few genes (Pin et al., 2012). The gap between plant breeding and crop modelling was bridged by Yin et al. (2003 and 2004). They showed opportunities for collaboration between modellers and breeders by recognizing the complementarity’s of QTL-mapping and crop growth modelling. Modelling Genotype × Environment interactions was considered as a major challenge. To understand gene to phenotype relationships and genotype by environment interactions combining physiological and genetic knowledge is essential (Edmeades et al., 2004). Especially, the up-scaling from gene to plant and crop for yield traits is highly complex (Boote et al., 2013). Further improvements in exploring improvements in potential yields can be made by including the plasticity of morphogenetic processes in mechanistic crop models. A new tool is functional–structural plant modelling (Vos et al., 2010). This type of modelling combines the quantification of three-dimensional plant structure (types of organs, initiation and expansion, canopy geometry, etc.) and the related physiological processes (photosynthesis, assimilate allocation). The potential application of these models is in ex-ante evaluation of genetic traits related to crop performance under specific growing conditions. It can also contribute also to the understanding of competition in mixed cropping systems (Zhu et al., 2014). 4.5. Research on ecological intensification Maintaining and developing agricultural biodiversity is important for future ecological intensification of the production of food, feed and bio-based feedstock. A plea for ecological intensification in cereal production systems was already made by Cassman (1999) at the end of the 19th century. Promising results are presented on studying ecological intensification not just on the field and farm level, by taking into account the role of biodiversity at the landscape scale (Tscharntke et al., 2012; Godfray et al., 2013; Schulp et al., 2014). Transitions in cropping systems and soil management (e.g. minimum tillage, soil conservation practices) do potentially also contribute to enrich biodiversity and intensify ecological

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processes in the soil (Tilman et al., 2002). The effects are however strongly determined by environmental conditions (Giller et al., 1997). A more comprehensive view on this concept including ecological services besides the production function of land was presented by Doré et al. (2011). They suggest that knowledge of natural ecosystems may also provide ‘sources of inspiration’ for ecological intensification of cropping systems. As building blocks of knowledge to guide ecological intensification are mentioned: (a) existing agronomic knowledge, (b) basic knowledge provided by plant sciences (e.g. genetics, ecophysiology, etc.), (c) knowledge of natural ecosystem functioning and d. farmers’ knowledge. In their conceptually rich paper they suggest to add meta-analysis and comparative analysis of agroecosystems to the existing methodology that is dominated by experiments and modelling. 5. Discussion and conclusions Major breakthroughs in agricultural sciences occurred from 1800 onwards when new insights on photosynthesis and mineral nutrition were incorporated in the theory on the growth of crops. Transitions in agricultural sciences are brought about by incorporating new findings and insights emerging from biological and biophysical sciences, by more advanced ways of experimentation and last but not least by quantitative methods and models for data analyses and processing (Kropff et al., 2001; Spiertz and Kropff, 2011). Communication among scientists and dissemination of knowledge to stakeholders and society have been important in the 20th century and will continue to play an important role (Appendix A). The rapidly growing demand for food, feed and fuel will require further improvements in experimental and modelling research on land and water management, crop productivity and resource-use efficiencies. A systems approach, including systems biology, combining knowledge at different scales and incorporating cutting-edge findings from the basic sciences into applied sciences will become important for making a great leap forward in developing agricultural science with impact. Multidisciplinary, integrated assessments of resource-use efficiencies, ecological services and economic profitability are needed to guide policymakers, consumers and farmers to develop efficient but also sustainable food systems (Bouwman et al., 2013). In contrast with the last decades of the 20th century, governments and funding agencies do give higher priority to strengthen the research capacities of developing countries. In the developed countries agricultural research has become more efficient by putting more emphasis on quality and impact in evaluating academic research institutions (Miller et al., 2013). Transitions in agricultural research will continue to depend on progress made in the related basic sciences. Therefore, an adequate public funding will be needed to maintain or even accelerate progress in sciences. This requires the support of the public at large. Acknowledgements Special thanks to colleagues of Wageningen University; especially, Prof. Maarten Koornneef, Prof. Ken Giller, Prof. Paul Struik and Dr. Xinyou Yinfor advice and constructive criticism. Furthermore, I acknowledge the suggestions made by two anonymous reviewers. Appendix A. Science and society: the role of leading scientists In the 20th century the impact of research on crop improvement and food production became more important and therefore draw the attention of a wider audience. This can be illustrated with some

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examples how the work of leading scientist did change the content and organization of agricultural sciences: a. The impact of the work of botanist and geneticist Nikolaj Vavilov (1887–1943) on identifying the centres of origin of cultivated plants and the founder of the N.I. Vavilov Institute of Plant Industry in St. Petersburg with the largest collection of plant genetic material in the world (Dvorak et al., 2011). b. The role of the plant pathologist and geneticist Norman Borlaugh (1914–2009) in breeding high-yielding, disease-resistant wheat varieties have had a big impact on food security in many countries, especially Mexico and India, from 1965 onwards (Sumberg et al., 2012). He was called the father of the Green Revolution. The impact of his research initiatives at the CGIAR institute for Maize and Wheat (CIMMYT) has had a great impact for the agronomy and breeding of high-yielding wheat varieties for almost five decades. He was also influential to mobilize critical mass in solving urgent threats by new strain rust diseases. The approach in solving the big risk of a new virulent strain of the wheat rust UG99 (Singh et al., 2008) is a good example. c. The role of geneticist M.S. Swaminathan (1925–) as scientist and administrator in leading the birth of India’s “Green Revolution”. Later he became well-known for his efforts in the field of an “evergreen revolution” and education of the poor in India. d. The role of the theoretical agronomist C.T. de Wit (1924–1993) has been important in embedding theories of physics and chemistry in agricultural and crop sciences. This new approach is shown in his publications on topics as: “Crop Transpiration”, “Crop Photosynthesis” and “Plant Competition”. Since the mid-60s he became the founding father a mechanistic crop growth modelling (De Wit, 1968). His scientific work shows a unique mix of theory, experiment and quantification of biological processes. To foster the role of science public visibility of cutting-edge research is needed. Great scientists of the past were aware of this role. They were member of prestigious societies (e.g. Royal Society in the UK) and travelled a lot abroad to meet colleagues, but also to communicate with a wider audience. Albert Einstein (1879–1955) was a missionary of science on the international stage (Renn, 2013). His travels and dissemination of the relativity theory had a great impact to make the public and policymakers aware of the role of science. Nowadays, in the Netherlands we experience the popularity of Robbert Dijkgraaf (1960–), currently Director of the Institute for Advanced Study (IAS) in Princeton. In special TV-shows the theory behind the “big bang” and the “string theory” based on mathematical physics was presented. As a successful scientist he is not only capable to communicate with professionals, but also to attract the attention of the young generation. The same applies for the cutting edge research by Hans Clevers (1957–) and co-workers of the Hubrecht Lab in The Netherlands on development of stem cells and the potential to use these phenomena in curing cancer (Clevers, 2006). Currently, there are many scientists, business man, “stars” and even politicians that play an important role in the debate on sustainable food production, human health, poverty and even more important food security and global change in 2050 and thereafter. Because of the power to get things done Bill Gates (1955–) is the most influential individual. The Bill and Melinda Gates Foundation does make more money available to improve food production and health in Africa than the US government through US-Aid. The role of the former Secretary-General of the UN, Kofi Annan (1938–), is still important to make institutional changes in the cooperation between countries and global institutions. In the Netherlands, writer and university professor Louise Fresco (1952–), is intensively engaged in public discussions on TV and in the scientific community to develop a balanced view on feeding a

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growing global population and improve the quality of life by more healthier diet choices. Writing scientific papers is most important to make progress in science possible; however, it is not the best instrument to make things done in the farming community and in the society. Dissemination of knowledge and communication of research ‘highlights’ through social media is becoming increasingly important. A good example of communication on prospects and pitfalls in introducing N2 fixation on in wider scale in food and feed crops in Africa is the N2Africa programme led by Ken Giller, Wageningen University, and funded by the Melinda and Bill Gates Foundation [see: www.n2africa.org].

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