Crop Yield Definition, Formula, Statistics

What Is Crop Yield?

Crop yield is a standard measurement of the amount of agricultural production harvested—yield of a crop—per unit of land area. Crop yield is the measure most often used for cereal, grain, or legumes; and typically is measured in bushels, tons, or pounds per acre in the U.S.

Sample sizes of a harvested crop are generally measured to determine the estimated crop yield for a larger region.

How Crop Yield Works

To estimate crop yield, producers usually count the amount of a given crop harvested in a sample area. Then the harvested crop is weighed, and the crop yield of the entire field is extrapolated from the sample.

For example, if a wheat producer counted 30 heads per foot squared, and each head contained 24 seeds, assuming a 1,000-kernel weight of 35 grams the crop yield estimate using the standard formula would be 30 x 24 x 35 x 0.04356 = 1,097 kg/acre. Moreover, since wheat is 27.215 kg/bu, the yield we estimated would be 40 bu/acre (1097/27.215) or 40 bushels per acre.

Crop yield can also refer to the actual seed generation from the plant. For example, a grain of wheat yielding three new grains of wheat would have a crop yield of 1:3. Sometimes crop yield is referred to as "agricultural output."

Crop Yield Statistics

The U.S. Department of Agriculture (USDA) produces charts and maps displaying crop yields, crop weather, and crop acreage animations to help U.S. farmers maximize agricultural product output. ​The USDA supplies many different statistics about crop yields for various agricultural products. For example, it publishes a monthly report of field crop yields for dozens of different products including barley, rice, tobacco, and wheat.

Part of this information is the absolute high and low yield for the entire history of the data series, some of which extend back over 150 years. Interestingly, for many products, the absolute low crop yield occurred in the 1930s during the time of the Great Depression and Dust Bowl years, while the absolute high crop yield occurred in the most recent years recorded.

Crop yields, farm efficiency, and agricultural product output in the U.S. have increased dramatically over the past decades as technology has advanced in farm automation, crop genetics, fertilizers, and pesticides.

Special Considerations​

Crop yield data is important not only in the U.S. but abroad as well. Declassified CIA documents show the U.S. government has used satellite reconnaissance imagery to estimate the crop yields of foreign countries.

This was particularly important in the 1960s during the height of the Cold War when the U.S. was using such methods to assess the agricultural health of China and the Soviet Union. Today, foreign countries frequently publish crop yield statistics on their government websites, similar to what the USDA does in the U.S.