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Nebraska Test Law put HP into perspective 
The keyword in all tractor discussions is horsepower. Every tractor is identified by its horsepower rating. The model number, alongside the horsepower rating, are the first labels
a manufacturer puts on a new model.
A 1908 Abenaque tractor was arbitrarily rated at 15 horsepower 12 years before Nebraska Tests were devised to create an industry standard. Dozens of tractor manufacturers attempted to display horsepower ratings on their models as best they could, settling on a dual rating of
drawbar HP/brake HP.
Aultman & Taylor built one of the largest early tractors. Their 1914 model was considered one of the best at the time. They rated it at 30 DB HP/60 Brake HP and called it the 30/60 model. It was a huge tractor weighing 24,450 pounds.
Deere entered the tractor business by purchasing Waterloo Gas Engine Company in 1918. Starting in 1914, Waterloo was one of the strongest competitors in the industry by introducing their lightweight tractor. It was first rated at 12 DB HP and 24 Brake HP.
That was the first tractor tested under the Nebraska Test Law (NTTL) in 1920. NTTL is a program administered by the University of Nebraska. It is in accordance with Nebraska law to test the performance of agricultural equipment to be sold in the U.S. for compliance with OECD standards. The NTTL has operated since 1920 as the standard referral for tractor performance in the United States.
The impetus for the Nebraska Test Act of 1919 came from Nebraska farmer Wilmot F. Crozier, who had been disappointed with the performance of several tractors he had bought.
Horsepower is a unit of measurement of power, or the rate at which work is done, usually about the output of engines or motors. Scottish engineer James Watt adapted the term in the late 18th century to compare the output of steam engines, turbines, and electric motors. The development of steam engines provided a reason to compare the output of horses with that of engines that could replace them. — (Reference: Encyclopedia Brittanica)
From 1920 on, tractor manufacturers lined up to test in Nebraska. Thousands of tests have been completed and continue daily., a significant source of tractor information, uses only three columns on its website: Model, horsepower, and year. In past years, the year of an automobile was the most important. Not so with tractors. Horsepower has always been the key statistic.
These categories have been used throughout the years:
Belt HP - How much horsepower (HP) is transferred by a belt from one pulley to another.
Brake HP - The available power of an engine, assessed by measuring the force needed to brake it.
PTO HP - The amount of HP available for running implements.
Engine HP - Refers to the power an engine produces. It is calculated through the energy needed to move 550 pounds one foot in one second or by the power required to move 33,000 pounds one foot in one minute.
Maximum (or Gross) HP - The most an engine produces on a test bench without air cleaner, radiator, or any accessories.
Tractor horsepower has always been on the increase. Before Nebraska Tests, ratings ran between 8 and 80. After the tests began, manufacturers used test results in their marketing, and the ratings were much more accurate for buyers.
Manufacturers have always had larger HP models on the drawing board for their next tractor announcement. Whether the larger tractors are the result of larger implements or vice versa, the increases have never stopped.
When Steiger released one of the earliest 300 HP tractors in the early 1960s, predictions were that no larger models would be on the future market. That was over 60 years ago, and horsepower has never stopped increasing. Models exceeding 700 are now on the market.
Future electric-powered tractors will play a part in the horsepower of the future.
The growing popularity of track undercarriages replacing wheels makes the bigger horsepower
tractors more beneficial. We can be sure that changes coming in the future cannot be easily predicted now.
Paul Wallem was raised on an Illinois dairy farm. He spent 13 years with corporate IH in domestic and foreign assignments. He resigned to own and operate two IH dealerships. He is the author of THE BREAKUP of IH and SUCCESSES AND INDUSTRY FIRSTS of IH. See all his books on Email your comments to