Marion Calmer has done independent, on-farm research for nearly 30 years. With more than 300 research plots on his farm, the Alpha, Ill., corn and soybean farmer has tested – and continues to test – practices to break through his soybean-yield barrier. Five have risen to the top. “You can't improve on things you don't measure,” he says.

"During the mid-1980s, my soybean yields averaged in the mid- to upper 40 bushels per acre," he says. “I have added about 20 bushels to the acre. The goal, naturally, is to shoot for 100 bushels, if it’s economical."

Here are his top five yield-busting tools:

1. Switch to no-till. After realizing in the 1980s that conventional tillage was not going to meet his long-term environmental goals, Calmer no-tilled soybeans. Before that, soybeans had been one of the most soil-erosive crops he had ever grown, he says.

"I started no-tilling beans into cornstalks. No-till requires trying different things to see what will work on your farm. If you keep a positive attitude, you can make it work," he says. "No-till really helped my yields during a dry 2012."

2. Narrow rows. Calmer also started planting corn in 15-inch rows in 1995. He adjusted his row cleaner at planting until he was able to pull residue from one row without throwing it into the next row. He has not touched his equipment settings since about 1998. The residue cover is uniform and provides a good environment for corn and soybeans to emerge in the spring.

He compared 30-inch to 15-inch rows in the 2008-2011 seasons, using the same planter, variety and inputs. He planted four replications per year for a total of 16 replications. The average response in changing to 15-inch rows was a 4-bushel yield increase per acre. The 2012 difference was even more.

"With the drought, we increased yield from 60 to 66 bushels per acre in 15-inch rows, or $72 more per acre," he says. "I believe there is still room for improvement."