In the early 1950s the average corn yield was around fifty bushels per acre. Flash forward to 2014 and the national average yield is pegged at around 170 bushels per acre. With the exceptions of severe weather (heat and drought), on average, corn yields have increased on average two bushel per acre per year. There are many factors contributing to this tripling of average yields involving all aspects of corn production. These factors include improved genetics through convention breeding and genetic engineering; improved understanding of soil fertility and nutrients; improved equipment to facilitate all aspects of corn production; development of a variety of reduced and no-tillage systems to conserve soil and moisture while improving organic matter levels; the development of integrated pest management systems for weed, disease, and insect control; and a better understanding of the ecology of crop fields including the importance of crop rotations.
It also helps that corn is a C4 plant. Without going into all the details, warm season grasses like corn have the ability to increase the rate of photosynthesis while plants like soybeans and wheat are C3 plants and by midmorning on a sunny day, they are photosynthesizing at their maximum level and increasing sunlight won’t increase the production of sugars. Meanwhile corn, provided adequate water, nutrients, and optimal temperatures can keep photosynthesizing faster. This and the other benefits of being a C4 plant provide producers a crop with a greater upside in terms of yield potential.  
Every year the National Corn Growers Association conducts a yield contest. These contests are strictly monitored with very precise rules. One is that when yields are above a certain threshold, the test is redone on a second part of the field. The benefits are two-fold. First, winning producers nationally and by state receive prizes, recognition and bragging rights. Second, and more importantly, by examining how these producers obtained their winning yields, all corn producers can benefit by adopting those practices.
This year, the overall winner was an irrigated producer from Valdosta Georgia with a winning yield of 503.7 bushels per acre. The other two irrigated the lowest yield for the top six irrigated winners was 422 bushels per acre. For the six categories with three winners per category, the average yield was over 350 bushel per acre. All but two categories are non-irrigated.  
For Kansas, the two top irrigated yields were over 335 bushels per acre. One Kansas farmer, Jason Taylor of White Cloud, had a 300 bushel per acre winner using no-till/strip-till. All the top three Kansas entrants in each category were well over 200 bushels per acre.
What is the importance of all this? With two billion more people on the way over the next two decades, food production must increase dramatically in all phases of agriculture, especially in the developed world. With our combination of soil, climate, technology, infrastructure, and an educated agricultural population, the United States must be one of the country’s leading the way to feed the world.