True, but Communism, not ammonia, killed more

"The synthesis of ammonia made possible the growth of the world's population. ... [B]y 1900, most of the good arable land in the world was already being farmed, so that increased food production could come most readily from the application of additional fertilizer. ... The Haber-Bosch process for synthesizing ammonia made it possible to increase the food supply and support the world's current population of about 6.2 billion people. In other words, in the twentieth century, the population of the world increased from about 1.6 to 6.2 billion largely because of the Haber-Bosch process. That increase in the human population alone makes the twentieth century unique in all of human history. ... More than that, it also made possible the industrial production of explosives, and, because Germany was the first to use this new technology, increased the confidence of its military leaders. And that was to be a crucially important factor contributing to the outbreak of world war in 1914."  Origins of the Modern World (2007)

http://www.delanceyplace.com/view_archives.php?2818&p=2818

The USSR and China killed millions with death camps and starvation.  Now we have a new global form of Marxism, intent on reversing the gains of the 20th century. Globalism.