The little field across the road from Owl Acres is planted in soybeans this year. Last year it was corn. It’s late summer now, and the soybeans (Glycine max) are beginning to dry and change color. Green leaves and stems are turning yellow, and the pods hanging from the plants are darkening to brown. When they’re dry enough, the combine will come and collect them. No weeds spoil the symmetry of neat rows of healthy plants burdened with seed pods as they march through the field. Those seed pods will yield an estimated 58 bushels of soybeans per acre.
My dad raised soybeans. He was in a constant fight with the weeds. In June, after the bean plants were established, he would drag the cultivator through the field, stirring up the soil between the rows to dislodge the weeds. Later in the summer, kids were hired to “walk the beans” using a hoe to dig out stubborn weeds. There’s none of that now. Careful applications of herbicides, fungicides and pesticides combined with patented designer beans that are immune to the herbicides eliminate the weeds.
The plants grow two to three feet tall with upright woody stems. In the spring, they produce little white or purple flowers, which in time produce curved seed pods with two to three seeds in each. A typical plant will produce 60 to 80 beans in 20 or more pods.
Soybeans are native to China. The earliest evidence of cultivation dates back to around 1100 B.C.E. In 1765, a colonist living in Savannah, Georgia imported soybeans in an effort to make soy sauce. Soy’s popularity waxed and waned in America. During World War I, people started using soy as a source of protein when meat was scarce. During the Great Depression, soy oil began to be part of people’s diets as well. Henry Ford became interested in soy for plastics to be used in his manufacturing processes. He even had a suit made of soy fibers. In 1904 George Washington Carver, a noted agricultural scientist working at Iowa State University, recommended soy as a source of oil and as a high protein animal feed. He also promoted the concept that rotating crops such as corn and cotton with soybean crops was highly beneficial to the soil.
Crop rotation is still a common practice. The reason is nitrogen. Nitrogen is a fundamental requirement for life for humans and plants alike. It makes up about 78% of the air we breathe. We breathe it in and we breathe it out, but we don’t use it directly from the air. We get what we need from the food we eat. Plants also need it for growth and DNA, but they can’t use the nitrogen in the air either. They have to get it in some other form from the soil. Some plants, including soybeans, peanuts, alfalfa and clover, can replenish usable nitrogen in the soil. They do this in partnership with bacteria called rhizobium. Shortly after emerging, the soybean plants develop root systems which include nodules on the roots. Rhizobium bacteria move into the nodules. There the bacteria take energy from the bean plant and in turn capture nitrogen from the air and “fix” it. Fixation is a chemical process that combines nitrogen from the air with hydrogen to make ammonia, and then reacts the ammonia with water to make ammonium. Plants can use the nitrogen in ammonium. The bean plant gets this “fixed” nitrogen compliments of the bacteria and uses it to grow. When it dies, it leaves it in the soil for next year’s corn.
Iowa is a leading producer of soybeans With 9.7 million acres planted to soybeans this year, the overall yield is estimated to be 558 million bushels in 2023 with market prices just under $15 per bushel.
Soy is everywhere these days. You find it in everything from plastic bags to salad oil, dogfood to industrial lubricants, cleaners to candy, paint to pancake flour. Iowa even has a law that state agencies must use soy ink in their printing. The farmers around Owl Acres will get a good crop of soybeans this year, and next year we’ll see corn or alfalfa in those fields.
Photo by Author. Alt text: Soybean pods covered with fine hairs hang in clusters from central plant stem