Trade wars with China. Arguments over a border wall with Mexico. Strained relations with South Korea. They all might sound like issues for politicians and the CEOs of multinational corporations, but among the Americans who have a vested interest in foreign affairs are a more unlikely group: family farmers in rural Nebraska.

Rick and Heidi Hammond and their daughter, Meghan, are one such Nebraskan family. The fifth and sixth generation of a miniature farming dynasty, they raise corn, soybeans and cattle while dealing with the uncertainties of the weather, farming machinery—and national and international politics. Along for ride is journalist Ted Genoways, who recounts the challenges the family has faced since they first arrived in the Cornhusker State in the 1860s in his new book, This Blessed Earth: A Year in the Life of an American Family Farm.

“I saw firsthand conversations about what to do at a particular moment on a soybean farm in rural Nebraska that was directly influenced by what was happening at that moment in trading in China,” Genoways says. Before, it was enough that we grew the most abundant and cheapest crops. But now, Genoways says farmers follow everything from trade agreements like the Trans-Pacific Partnership to the debate over NAFTA and immigration from Mexico—to which the Mexican government has suggested it might stop imports of American corn.

“There are many influences on who decides to trade with us and certainly right now there’s a great deal of nervousness over what Trump’s volatile relations overseas will mean for sales of grains in particular, but also our meat sales and really all ag products,” Genoways says.

This Blessed Earth: A Year in the Life of an American Family Farm "This Blessed Earth" is both a concise exploration of the history of the American small farm and a vivid, nuanced portrait of one family’s fight to preserve their legacy and the life they love. Buy

The system in place today means that midsized family-run farms like the Hammonds’ are almost as dependent on the decisions of politicians in Washington, D.C., as they are on the sun and rain in Nebraska. How did we get to the point where agriculture was so closely tied to American geopolitics and global events?

Abraham Lincoln, eager to preserve a West free of slavery, signed the Homestead Act in 1862. It granted cheap plots of land to any citizen who had never taken up arms against the federal government and funneled money from the purchase of those lands into schools for agriculture and mechanical arts (known as A&Ms). Lincoln also signed the Pacific Railway Act, providing land grants for railroad companies. Among the young men lured west by the promise of a life of agriculture and freedom was Thomas Barber, Heidi Hammond’s great-great-grandfather and the first of his clan to forge a life on the frontier.

But farmers’ yields over the second half the of the 19th century were unpredictable, even as the amount of land overtaken by crops expanded. In 1874, nearly three-fourths of the country’s crops were chewed to nothing by swarming grasshoppers, and then came the Bank Panic of 1893, and then multiple years of drought. If farmers wanted more reliable yields, and the nation a ready source of food, something had to be done.

Along came two men who would forever change how and what we grow. First was Henry A. Wallace, an innovator experimenting with corn hybridization. He developed a drought-resistant variety just as the Dust Bowl hit, and for his work was appointed Secretary of Agriculture by Franklin Roosevelt in 1933. Within a decade, the share of America’s corn that came from hybrid seeds had grown from 1 percent to more than 75. From there, Wallace went on to become Roosevelt’s vice president and convinced him to establish a federal grain reserve. In years of high production, the Department of Agriculture would store grain, and release it during lower production years to keep prices down.

Then there was famous car manufacturer Henry Ford. After losing $120 million in the early 1930s due to a decline in sales of trucks and tractors, Ford turned to soybeans as a way to “rescue” debt-ridden farmers and engage in a new industry. He promoted soybeans mainly for their chemurgic applications, but also stocked his company commissary with soy milk ice cream and baked goods made of soy flour. Soybeans had better yields than corn in periods of drought, and after the bombing of Pearl Harbor, the government pushed for even greater yields, since the beans provided a source of edible fat and oil. Between 1943 and 1945 the country’s soybean production went from 78 million bushels to 193 million—and when the war ended, those beans could feed the cattle that Americans were so eager to eat as they had before the war after years of rationing.

Wallace’s hybrid varieties came with one setback, however they grew so quickly that they rapidly depleted nitrogen from the soil. Enter Monsanto and other munitions manufacturers like DuPont, whose business had boomed during World War II. When peace was struck, they were starved for customers. Soon these companies were churning out chemical fertilizers and pesticides for use by farmers who in turn grew year after year of surplus grains, using ever more precise hybrid varieties of corn and soybeans. The stage was set for an agricultural system that could be further manipulated by a federal government eager to undercut grain commodities of Communist countries during the Cold War and buy allies with cheap produce.

“We’ve really built a system where we’re exporting grains in large numbers in order to have some influence around the world, not just with our friends but also with our enemies, by controlling the food supply,” Genoways says. “What that means is that they’re not only dependent on us for supply, but we’re also dependent on them for demand.”

That dependency can mean the survival or failure of a family farm, and family-owned farms still comprise 99 percent of the 2.1 million farms in the United States. As grain prices have fallen over the past five years, more and more farmers are feeling the squeeze, Genoways says—and that’s not even accounting for the fact that in 2015, U.S. agricultural exports were at their lowest value in five years. Little wonder that farmers closely watch foreign markets and the evolving relationship the U.S. has with its trading partners, like China and Mexico.

For Genoways, it’s time people realized the complexity of farming in a global system, where choices made by the government will have a direct impact on farmers and the food we eat. He hopes readers will come away from his book with that new appreciation. “What they do is incredibly valuable, and the heritage they represent is valuable, and we’re trying to preserve that way of life and make it sustainable,” Genoways says.