**1. Introduction**

Corn (*Zea mays*), also called maize or field corn, is the most important cereal in the world, with annual global production exceeding that of wheat and rice. In 2017, corn production accounted for 41% of total grain production in the world [1]. While corn is a staple food in parts of the world, it has many uses, including animal feed, biofuel and sweetener. This chapter provides an overview of the evolving role of corn in agriculture.

Corn was first domesticated in southern Mexico about 9000 years ago [2, 3]. Its closest wild relative is teosinte, a wild grass of Mexico, Guatemala and Honduras. A major puzzle is the great genetic differences between teosinte and corn, indicating how key mutations and human selection contributed to genetic evolution [4]. After the Columbian exchange, corn production spread throughout the world. Corn is a highly productive crop with the ability to exploit

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

available soil nutrients. As a C4 plant, corn has some photosynthetic advantages in capturing solar energy in warm weather compared to C3 crops such as wheat, rice and soybean. Due to its high productivity under various climate conditions, corn is now the largest grain crop in the world [1]. Favorable agro-climatic conditions in the US "Corn Belt" have made the US the largest corn producer. In 2017, corn production in the US accounted for 35% of world corn production [1].

we reflect on what may come next. Some evidence suggests that agricultural productivity growth may be slowing down, raising concerns about our ability to feed a growing world

Genetic selection has been a very important driver of agricultural productivity. The process started some 9000 years ago in Mexico when corn was first "selected" and evolved from its wild ancestor [2]. Over the centuries, accidental mutations and some intentional selections contributed to beneficial changes [3]. But as **Figure 1** indicates, the rate of genetic improvement was very slow before 1940. Genetic selection was then based mostly on traditional breeding methods trying to combine desirable characteristics of each parent into the progeny. Applied to crops, farmers used selective breeding to pass on desirable traits while omitting undesirable ones. The desirable traits included higher yield and better quality as well as improved adaptation to local agro-climatic and ecological conditions. When applied by farmers, the

The early part of the twentieth century saw the rise of modern genetics and its applications to plant breeding. The discovery of hybrid vigor led to the development of hybrid seed corn and rapid improvements in corn productivity [5, 8]. The higher corn yields stimulated the rapid adoption of hybrid seed corn among US farmers [8, 9]. The new corn hybrids also contributed to the development of a seed corn industry that focused on refined genetic selection [10]. The increased intensity of genetic selection contributed to the development of improved varieties that were better at capturing soil nutrients and more resistant to diseases [5]. As **Figure 1** shows, the result has been decades of genetic improvements and rapid and sustained growth in corn yields. Starting in the 1980s, progress in biotechnology revolutionized genetic selection. The identifica-

genetic selection. Eventually, this process led to the development of genetically engineered (GE) corn hybrids that, along with the patenting of GE seeds, stimulated the growth of biotechnology in agriculture. The first GE corn hybrids became commercially available in the US in 1996, with US farmers rapidly adopting the technology. In 2017, more than 90% of all corn planted in the US was GE [12]. The rapid adoption of GE corn in the US led to significant productivity improvements [13]. Over the last two decades, the adoption of GE seed in agriculture has proceeded around the world, though at different rates depending on each country's regulations [14].

Two major types of GE traits are currently available in the hybrid seed corn market: those providing insect resistance (IR) (commercially available in corn in 1996) and those providing herbicide tolerance (HT) (commercially available for corn in 1998). Hybrid seed corn contains these traits either singly or combined as stacks or pyramids, so that a single hybrid is both IR

We now know that horizontal gene transfers across species are not uncommon and that they played an important role

technologies opened new opportunities for

Corn Productivity: The Role of Management and Biotechnology

http://dx.doi.org/10.5772/intechopen.77054

15

population (e.g., [7]). We ponder these prospects as they apply to corn production.

selection intensity was low, generating slow genetic changes.

tion of genes and the refinements in gene transfer<sup>2</sup>

to multiple pests and HT to more than one herbicide.

2

in the evolution of life (e.g., [11]).

**2. Corn productivity**

The rise of corn as the most important cereal in the world has been associated with important improvements in its productivity [5]. **Figure 1** illustrates the evolution of the average corn yield on US farms from 1870 to 2017 [6]. **Figure 1** shows that corn productivity was basically stagnant before 1940: during the period 1870–1940, US average corn yields stayed within a narrow range between 20 and 30 bu/acre. (between 1200 and 1900 kg/ha)<sup>1</sup> Starting in 1940, a period of fast and steady rise in corn productivity began and continues to this time. US average corn yield increased from 28.9 bu/acre (1.81 metric tons/ha) in 1940 to 176.6 bu/acre (11.1 metric tons/ha) in 2017 [6]. This amazing achievement means that a given area of land can produce 6.1 times more corn in 2017 than in 1940, which corresponds to an average annual growth rate of 2.35%, reflecting the rapid technological progress sustained over the last seven decades. This achievement raises two questions. First, what are the sources of this growth in corn productivity? Second, is it likely to continue in the future? Below, we discuss the role played by two key drivers of corn productivity: improved genetics and improved management. We also consider the corn market and its evolving prices. Finally,

**Figure 1.** Historical corn yield, US. Source: The corn yield is measured in dollar per bushel, as reported by USDA-NASS [6].

1 1 bushel of corn equals 25.40 kg and 1 acre of land equals 0.4047 hectare. Thus, 1 bu/acre = 62.77 kg/hectare. we reflect on what may come next. Some evidence suggests that agricultural productivity growth may be slowing down, raising concerns about our ability to feed a growing world population (e.g., [7]). We ponder these prospects as they apply to corn production.
